Volumetrics Diet

Diet Reference Archive: a book-based eating approach built on energy density

Volumetrics Diet

An eating approach from the books of Barbara Rolls, a Penn State nutrition scientist, that steers meals toward foods with few calories for their weight, such as vegetables, fruit, broth-based soups and whole grains. It is sold and studied mainly as a way to eat less without feeling hungry, and this page also carries the wider research on energy density, labeled as research on energy density rather than on the named plan.

Family: Guideline-endorsed and evidence-based dietary patterns, listed there on the archive index Promoted by: Barbara Rolls, through 3 Volumetrics books First appeared: 2000, as a book GRADE: Low for regain of measured weight over 21 months after a 12-week weight-loss phase, adults in primary care given the Volumetrics book and energy density lessons during maintenance compared with lifestyle maintenance alone, one randomized trial; this page's own judgment

ON THIS PAGE

1. In brief
2. Overview
3. In practice
4. For the coach
5. The evidence (opens on request)
6. Mechanisms (opens on request)
7. Risks, contraindications and myths (opens on request)
8. Key terms
9. Review questions
10. References
11. Evidence rating and review record

The summary and sections 1 to 3 are the short version and are open when the page loads. Sections 4 to 6 hold the research detail, the biology, and the cautions. Each of those opens when you select its heading, and you can read the page without opening them. The evidence section keeps 2 kinds of research apart: studies that tested the Volumetrics plan as Rolls published it, and the much larger body of research on energy density in general. Back to the Diet Reference Archive index.

In brief

What is it? A way of choosing food by its energy density, the number of calories in a given weight of food. Barbara Rolls, a nutrition scientist at Penn State, set it out in 3 books from 2000 to 2012. The books sort foods into 4 groups, from very low energy density, such as most vegetables, fruit and broth-based soups, to high, such as chips, butter and candy, and build meals mostly from the first 2 groups so that portions stay large while calories fall (Lowe et al., 2010; Rolls, 2016; Schueller, 2026). No food is forbidden.

Does it work? Two different questions have 2 different answers. Research on energy density itself is large: in short controlled studies, people served lower-energy-density food ate less over a day without eating more food by weight (Klos et al., 2023; Robinson et al., 2022), and in a year-long trial women counseled to add water-rich foods to a lower-fat diet lost more weight at 6 months than women counseled on fat alone, with a smaller, uncertain difference at 12 months (Ello-Martin et al., 2007). Cohort studies of energy density and weight gain, type 2 diabetes and cancer disagree with each other, and in a large UK cohort a slightly higher risk of death with higher energy density was no longer seen once overall diet quality was taken into account (Wang et al., 2026).

Research on the named plan is thin. The searches for this page found 2 randomized trials that handed participants a Volumetrics book. In one, adults in primary care who added the book and energy density lessons while keeping off lost weight regained less than a comparison group, but the same lessons combined with meal replacements did not, and the certainty is low (Lowe et al., 2014). In the other, a workplace study, the book and lessons did not change measured weight (Lowe et al., 2010).

Is it safe? It removes no food group, and in older adults in Spain lower-energy-density eating went with better nutrient intakes (Schröder et al., 2008). No trial found by these searches reported harm from the plan, but none was designed to look for it.

The cautions concern particular people: someone taking insulin or a sulfonylurea who eats less can have low blood sugar (National Institute of Diabetes and Digestive and Kidney Diseases, n.d.-b), a sudden jump in leafy greens can change how warfarin works (National Institutes of Health Office of Dietary Supplements, 2021), and for people whose problem is eating too little, a diet that fills the stomach with few calories works against what they need. A person on these medicines keeps the prescriber informed before a substantial change in eating; a possible low blood sugar episode is treated first under the person's own plan, with emergency help if symptoms are severe or the person cannot manage the episode under that plan, and the prescriber is told afterward.

Who should not do it without talking to a doctor or dietitian first? Anyone taking insulin, a sulfonylurea, blood pressure medicine, warfarin or a weight-loss medicine such as a GLP-1 drug. Anyone with kidney disease, whose needs depend on the stage of disease, lab results and dialysis. Anyone who is pregnant or breastfeeding, any child or teenager, and any older adult with a small appetite or weight loss they did not intend. Athletes and very active people with high energy needs. And anyone with a current or past eating disorder or disordered eating, because the plan is built around eating fewer calories and a low-energy-density diet is a documented concern in recovery from anorexia nervosa (Schebendach et al., 2008, 2012).

Related pages: Mayo Clinic Diet, which builds on the same idea; Noom, whose color labels rest on calorie density; Vegan Diet and Whole-Food Plant-Based Diet, often low in energy density; Intermittent Fasting, the comparison in one trial; Meal Replacement Programs, paired with the plan in another; and Mindful Eating and Intuitive Eating, approaches built around hunger and fullness rather than calories. Full list on the archive index.

1. Overview

What you eat

The plan is organized around energy density, the number of calories in a given weight of food. Water adds weight to food without adding calories, fiber adds bulk with few calories, and fat carries the most calories for its weight, so foods high in water and fiber and low in fat are the ones the plan puts at the center of the plate (Rolls, 2017). Because broth-based soups sit in the very low group and crackers in the high group, the same calories buy a much larger portion of soup than of crackers.

The books sort foods into 4 groups. A workplace trial that used the first book gives its ranges: very low energy density, under 0.6 calories per gram; low, 0.6 to 1.5; medium, 1.6 to 3.9; and high, 4.0 to 9.0 (Lowe et al., 2010, citing Rolls and Barnett). U.S. News & World Report gives the same 4 groups with examples. Very low: non-starchy vegetables and fruit, broth-based soups and nonfat milk. Low: starchy vegetables, whole grains such as brown rice and whole-wheat pasta, lean fish and poultry, beans and lentils, and low-fat dairy. Medium: breads, desserts, cheese and fattier meats. High: fried foods, chips, candy, crackers, nuts, butter and oils (Schueller, 2026).

A person eats mostly from the first 2 groups and smaller portions from the other 2. U.S. News describes each day as breakfast, lunch, dinner, a couple of snacks and dessert (Schueller, 2026). The most recent book, The Ultimate Volumetrics Diet (2012), adds a 12-week plan and more than 100 recipes, according to Penn State's announcement of it (Penn State News, 2012). The books themselves were not opened for this page, so the plan is described here from these published accounts of it.

What you avoid or limit

Nothing is off limits. The plan limits rather than removes the medium and high groups, and asks a person to eat them in smaller portions. Rolls put it this way in a U.S. News interview: the book does not tell people to avoid higher-calorie-density foods but to manage portions to meet a calorie goal (Schueller, 2026). Caloric drinks get particular attention because they add calories without much fullness; one trial labeled a volumetrics diet barred caloric drinks altogether (Cloos et al., 2025), although its rules came from German nutrition societies rather than from Rolls's books. These are guidelines, not hard rules, and how closely a person follows them is up to them.

Where it came from

Barbara Rolls has studied hunger, fullness and food intake for decades; when Penn State announced her 2012 book, she was a professor of nutritional sciences there and held the Helen A. Guthrie Chair in Nutrition (Penn State News, 2012). Her laboratory's controlled studies served meals that differed in energy density, portion size or both, and measured how much people ate. In her 2009 review of that work, people tended to eat a fairly consistent weight of food, so lowering the energy density of what was served lowered the calories eaten; the reasons for that tendency were not yet well understood, and studies lasting more than several days were few (Rolls, 2009). In a typical result, women served all their meals for 2 days at 75 percent of the usual energy density ate about 575 fewer calories a day, without rating themselves hungrier (Rolls et al., 2006).

Rolls turned that research into books for the public: a first book written with Robert Barnett in 2000, listed in catalogs both as Volumetrics: Feel Full on Fewer Calories and as The Volumetrics Weight-Control Plan; The Volumetrics Eating Plan in 2005; and The Ultimate Volumetrics Diet, written with Mindy Hermann, in 2012 (Open Library, n.d.-a, n.d.-b, n.d.-c, n.d.-d; Rolls, 2016). Penn State reported that one of the earlier books topped the New York Times paperback advice list in 2007 (Penn State News, 2012). Rolls has written that publishing popular books felt risky for her scientific standing, because translating research for the public means glossing over unsettled questions (Rolls, 2016).

The plan is a book-based approach, not a company. U.S. News describes it as not a commercial diet, with no subscription or products to buy (Schueller, 2026). Penn State Extension, the university's outreach service, runs a paid class series based on it, described under cost below.

What it claims to do

The claims come from the books' author and from writers about the plan, and they are reported here as claims. Rolls's central claim, in Penn State's words, is that lowering the calorie density, or calories per bite, of food can help people feel full while eating fewer calories; she is quoted saying that there is no magic way around eating fewer calories than the body burns, but that cutting calories does not have to leave a person hungry (Penn State News, 2012). Penn State Extension calls the plan a scientifically backed approach for managing weight while eating satisfying and nutritious foods (Penn State Extension, n.d.).

U.S. News's profile goes further. It says the diet has proven health benefits based on independent research, that a person is likely to lose weight following it and will not go hungry, and that it can help prevent heart disease and diabetes; it also notes that there are few research studies on the Volumetrics diet itself (Schueller, 2026). Section 4 sets those statements beside what the searches for this page found, and keeps the plan's own research apart from research on energy density in general.

U.S. News lists the Volumetrics Diet among the 10 diets on its list of top expert-recommended diets overall and among the 9 on its list of expert-recommended diets for weight loss; its profile shows a score of 3.8 in the weight-loss category (Burdeos, n.d.; Jones, n.d.; Schueller, 2026). U.S. News says a category score is the share of its expert panelists who recommended the diet for that goal, multiplied by 5, from ratings released in January 2025 (Schueller, 2025). That is U.S. News's rating, a summary of expert opinion rather than a study.

What it gets right

Much of what the plan asks for matches current heart-health guidance. The American Heart Association's 2026 statement lists matching energy intake and expenditure to keep a healthy body weight, eating plenty of vegetables and fruits, choosing mostly whole grains, choosing healthy protein sources, using unsaturated fats in place of saturated fats, choosing minimally processed foods, minimizing added sugars and reducing sodium (Lichtenstein et al., 2026). A low-energy-density pattern leans on the first several of these, and it removes no food group.

The plan also takes hunger seriously. Many weight-loss approaches ask people to eat less of everything; this one asks them to change what fills the plate, which is the part a person can see and feel. In the year-long trial described in section 4, women who were taught to add water-rich foods reported less hunger than women taught to cut fat alone (Ello-Martin et al., 2007). These are the parts a coach can honor in a client's reasons without endorsing the whole package.

How clients describe it, and what it gets confused with

Clients say "I'm doing Volumetrics," "I eat volume," "I fill up on vegetables first," "I'm doing volume eating," "I start every meal with soup or a salad," or "I eat the low-calorie-density foods." Some have read one of the books, some follow social media accounts that use the word volume, and some have picked up the idea from another program. Ask which one before assuming.

It is confused with the Mayo Clinic Diet, whose food pyramid rests on the same idea that vegetables and fruit are filling for their calories; with Noom, whose green, yellow and orange food labels follow calorie density; and with Calorie Counting and Tracking Apps, since the plan asks people to think about calories without requiring them to count. It is not a meal-replacement program, which Meal Replacement Programs covers, and it is not the same as Vegan Diet or Whole-Food Plant-Based Diet eating, which are often low in energy density but are defined by which foods they include or exclude. It is also not Clean Eating, a label with no fixed definition.

2. In practice

A typical day of eating

The books were not opened for this page, so the day below is an illustration built from the food groups described in section 1, not a menu from the books. Breakfast might be oatmeal cooked with milk and topped with berries, or eggs scrambled with mushrooms and peppers, which is the kind of swap U.S. News describes (Schueller, 2026). Lunch might start with a bowl of broth-based vegetable soup, then a sandwich on whole-wheat bread with turkey and plenty of lettuce and tomato. A snack could be an apple, grapes or carrots with a little hummus.

Dinner might be a large salad with a light dressing, then fish or beans with brown rice, the rice portion halved and the space on the plate filled with roasted vegetables. Dessert, which the plan allows, might be fruit with yogurt, or a small portion of something richer. Nothing on the list is unusual food. What changes for most people is the proportion: more vegetables, fruit and soup at the start and center of meals, smaller portions of fried foods, chips, cheese and sweets, and water or other calorie-free drinks in place of sweetened ones.

Cost, products, and who profits

The plan needs no special products. U.S. News says it is not a commercial diet, with no subscription or products to buy, and that Rolls's books guide a person but are not necessary to follow the eating pattern (Schueller, 2026). Library catalog records list the books under HarperCollins and related names, among them Harper Paperbacks, HarperTorch and, for The Ultimate Volumetrics Diet, William Morrow Cookbooks (Open Library, n.d.-a, n.d.-b, n.d.-c, n.d.-d). The searches for this page could not read a current book price: the publisher's page refused the browser on October 19, 2026, and a retailer's page stopped at a security check, so no price is given here.

Penn State Extension sells a 6-session live online class series, The Volumetrics Weigh of Life: Weight Management Plan, 1 hour a week for 6 weeks. On October 19, 2026, its page listed the series at $30.00, with the next series beginning January 6, 2027, and recordings available to registrants for 6 months (Penn State Extension, n.d.). In 2023 Penn State described an in-person version of the same series at $40 (Penn State News, 2023).

Several parties make money when a client follows the plan. Rolls receives royalties from the sale of the Volumetrics books; she has declared this in her research papers, for example in a 2017 review and a 2018 review with a colleague (Rolls, 2017; Smethers & Rolls, 2018). The publishers sell the books, and Penn State Extension collects class fees. The plan's ideas also appear inside other products: a registration of a study that Noom Inc. sponsored describes the app's color system for foods as founded on calorie density, naming the Volumetrics diet and Barbara Rolls (Noom Inc., 2021). The sources opened for this page do not say whether Rolls or the publishers receive anything from that use.

The food itself is ordinary grocery food, and what it costs depends on how cost is measured. Low-energy-density foods such as fresh vegetables and fruit cost more per calorie than energy-dense foods: in Seattle supermarket prices from 2004 to 2006, the least energy-dense fifth of 372 foods cost $18.16 per 1,000 calories against $1.76 for the most energy-dense fifth, and the least energy-dense foods rose 19.5 percent in price over 2 years (Monsivais & Drewnowski, 2007). Other analysts argue that cost per calorie is the wrong measure, because in an online supermarket produce cost more per calorie than snacks but less per gram and less per package (Lipsky, 2009), and an analysis of 4,430 foods eaten by U.S. adults, read in abstract only, found almost no statistical support for energy-dense foods being cheaper once the way the measure is built was accounted for (Davis & Carlson, 2015).

For someone with little money, the practical points are these: frozen and canned vegetables without added sauces, dried or canned beans, oats, potatoes, seasonal fruit and homemade soups are low in energy density and inexpensive, while bagged salads, berries out of season and lean fresh fish cost more. That sentence is observation, not a measured finding. A library copy of a book, or no book at all, delivers the central idea without cost.

Environmental footprint

The searches for this page did not identify a study of the environmental footprint of the Volumetrics plan itself. Two French studies bear on energy density and footprint in general. In a modeling study of 483 supermarket foods, grains and sweets had the lowest greenhouse gas emissions, per 100 grams and per 100 calories, but were high in energy density and low in nutrients; meat and dairy had higher emissions, and their gap with other foods looked much smaller when counted per 100 calories than per 100 grams. In general, more nutrient-dense foods carried higher emissions per 100 calories (Drewnowski et al., 2015). In the self-selected diets of 1,918 French adults, the diets that were both lower in emissions and higher in nutritional quality had a below-average energy density, energy content and cost, and a larger share of plant foods (Masset et al., 2014).

Both are modeled or survey estimates, not measurements of people following a plan. Because a low-energy-density diet can be built mostly on vegetables, legumes and grains or mostly on lean meat, fish and nonfat dairy, its footprint depends mostly on which foods a person chooses within it.

Cultural fit

Because the plan works by food properties rather than by named foods, most food traditions can be fitted to it: soups, stews, salads, vegetable dishes, rice with beans and steamed or braised dishes are low or moderate in energy density in many cuisines. U.S. News says the recipes can be adapted for vegan, vegetarian, gluten-free, halal and kosher eating (Schueller, 2026). Two features fit some lives less easily. Foods central to many traditions, such as fried breads, nut-based sauces, cheeses and cured meats, sit in the medium and high groups, and a person may hear the groups as a judgment on their family's food. And the plan's emphasis on fresh produce and home cooking assumes time, storage and store access that not every household has.

The people studied so far are not a broad sample. The year-long energy density trial enrolled women, more than 9 in 10 of them White (Ello-Martin et al., 2007). The primary care trial was more varied, with about 2 in 3 participants African American and 9 in 10 women (Lowe et al., 2014). The workplace trial enrolled hospital and university employees in Philadelphia (Lowe et al., 2010).

What makes people stop

The studies give dropout figures more often than reasons. In the year-long trial, 71 of 97 women stayed to 12 months, and the reasons most often given for leaving were schedule conflicts with counseling sessions and moving away (Ello-Martin et al., 2007). In the workplace trial, 42.7 percent had dropped out by the 12-month follow-up, significantly more from the group that received the book and classes (Lowe et al., 2010). In a 12-week trial of a rule-based low-energy-density diet, participants reported sticking to the rule on 5.29 days a week on average, fewer than the 5.78 days reported by a group following an eating window, and adherence in the low-energy-density group fell from 74 to 65 percent over the 12 weeks (Cloos et al., 2025).

Beyond those figures, what follows is observation. U.S. News names meal planning and portioning as tedious for some people (Schueller, 2026), and the authors of the 12-week trial noted that keeping every meal under an energy density limit is hard when foods are combined (Cloos et al., 2025). Other likely reasons are the cooking time, the cost of fresh produce, meals with family members who eat differently, and slower weight change than a client hoped for.

What happens when you stop

The searches for this page did not identify a study that followed people after they stopped using a Volumetrics book. Three trials of energy density approaches followed people after the intensive part of treatment ended. In the primary care trial, the group that received the book and energy density lessons regained an average of 0.52 kilograms from the start of maintenance to the last follow-up, 2 years after treatment ended, against 5.06 kilograms in the lifestyle-only group, while the group that received the same lessons with meal replacements regained 4.55 kilograms (Lowe et al., 2014). In the year-long trial, both groups regained an average of 0.7 kilograms in the second 6 months, when contact was less frequent (Ello-Martin et al., 2007).

In a trial in 2,718 breast cancer survivors, read here in abstract only, a multicomponent diet intervention lowered energy density and kept it lower for 4 years, and produced a small weight difference at 1 year that was gone by 4 years (Saquib et al., 2008). The Meal Replacement Programs page describes Lowe et al. (2018), a broader home-food-environment program that borrowed Volumetrics ideas. The plan is designed not to end, so the more useful question for a client may be what helps the changes last.

Common variations

The plan has appeared in 3 books, in 2000, 2005 and 2012 (Open Library, n.d.-a, n.d.-c, n.d.-d). The books were not opened for this page, so their differences are described only where a source says: Penn State describes the 2012 book as building on the 2 earlier ones and adding a 12-week plan and more than 100 recipes (Penn State News, 2012). Penn State Extension's class series teaches the plan in 6 sessions (Penn State Extension, n.d.). Other programs borrow the idea: the Mayo Clinic Diet builds its pyramid on vegetables and fruit being filling for their calories, and Noom labels foods by calorie density.

Researchers have also used the name for their own rules. A 2025 German trial called its intervention a volumetrics diet and defined it as keeping every meal at or below 1.5 calories per gram with no caloric drinks, using limits from German nutrition societies rather than Rolls's books (Cloos et al., 2025). And on social media many people describe volume eating, filling up on large portions of low-calorie foods; the sources opened for this page do not describe how closely that follows the books, so a coach asks what a client means by it.

3. For the coach

SCOPE OF PRACTICE

A health and wellness coach does not prescribe, adjust, endorse, or discourage the Volumetrics plan or any other way of eating, and does not diagnose or treat. The coach helps the client understand what they have chosen, notice how it is going, and decide what to do next. The plan is framed around eating fewer calories, so the coach also keeps weight in its place: a number a study measured, never a goal the coach sets or a measure of whether the client is succeeding. A client who wants an individual eating plan for a medical condition is describing the work of a registered dietitian.

The plan's risks fall on particular groups rather than on healthy adults in general. For a client in any of these groups, the coach's role includes making sure the client has medical oversight for the change. Insulin or a sulfonylurea: the client keeps the prescriber informed before a substantial change in eating, because eating less can bring on low blood sugar. Blood pressure medicine or a weight-loss medicine such as a GLP-1 drug: the client keeps the prescriber informed before a substantial change in eating, and any change to the medicine is the prescriber's decision. Warfarin: the client keeps the prescriber informed before a substantial change in vitamin K intake, such as many more leafy greens.

Kidney disease: the kidney care team, because needs depend on the stage of disease, lab results and dialysis. Pregnancy or breastfeeding: the obstetric clinician and a registered dietitian. Children and teenagers: the family and the pediatric clinician. An older adult with a small appetite or weight loss they did not intend: the physician and a dietitian, before the plan. An athlete or very active person with high energy needs: a sports dietitian. A current or past eating disorder or disordered eating: the client's clinician, through the coach’s own referral process or an existing care plan, before the plan is discussed further.

Who does what

The physician

Decides whether this change in eating is medically appropriate for this person, given their conditions, medicines and nutritional needs. Orders and reads the labs that matter, such as blood sugar and HbA1c, kidney function and potassium, and blood lipids, and measures blood pressure over time. Adjusts any medicine the change affects: insulin and sulfonylureas as eating falls, blood pressure medicine as pressure changes, warfarin around vitamin K intake, and any weight-loss medicine. Evaluates weight a person is losing without meaning to.

The registered dietitian

Designs and monitors an individual eating plan, which a book cannot do. For this plan that usually means checking whether a person is eating enough energy and protein, especially an older adult, an athlete or someone on a weight-loss medicine; fitting a high-fiber, high-produce pattern to diabetes, kidney disease or a digestive condition; and fitting the plan to a budget, a food tradition or an allergy.

The health and wellness coach

Helps the client get clear about what they want from the plan and why, and whether the plan's ideas fit their life, kitchen and budget. Helps them choose 1 or 2 changes to start with, such as a vegetable at lunch or soup before dinner, plan for meals where the changes are hardest, and notice how it is going in their own terms: hunger, energy, sleep, mood, enjoyment of food and the habits themselves, not only the scale. With the client's permission, can share general information about what the research does and does not show. Holds the referral line when a question belongs to a clinician.

What a client bringing this diet needs

Clients bring Volumetrics for a handful of reasons: they are tired of being hungry on diets, a friend lent them a book, they saw it on a list of top-rated diets, or they want an approach without forbidden foods or a subscription. Some are already taking a weight-loss medicine and want help with eating while on it. Some say they want to lose weight, and some want to eat more vegetables or feel better after meals. The reason shapes the conversation.

What the coaching conversation can offer that the book cannot is room to separate the client's own goal from the diet's promises. A coach can help a client decide which change matters most to them, what "full" and "satisfied" feel like, and how to tell whether a change is working apart from the scale. When a client says a diet is "ranked number one," a coach can recognize the rating, then ask what drew the client to it.

What to ask

• "What made Volumetrics appealing to you?"
• "Which change feels easiest to start with, and which one feels furthest away?"
• "How would you know, a few months from now, that this is working for you, apart from the scale?"

Referral red flags

A client on insulin or a sulfonylurea who reports shakiness, sweating or confusion may be having a low blood sugar episode right now. The first step is the one in their own diabetes plan for treating it, with emergency help if the symptoms are severe or the person cannot manage the episode under their plan; telling the prescriber is the separate step that follows. Eating fewer carbohydrates, or skipping or delaying meals, makes low blood sugar more likely for people taking these medicines (National Institute of Diabetes and Digestive and Kidney Diseases, n.d.-b), so the client keeps the prescriber informed before a substantial change in eating.

A client on blood pressure medicine who reports dizziness or lightheadedness, especially on standing, should tell the prescriber, who can work out the cause; the coach does not guess at it. Before a substantial change in vitamin K intake, a client taking warfarin keeps the prescriber informed, because people taking warfarin need a consistent intake of vitamin K (National Institutes of Health Office of Dietary Supplements, 2021). A client taking a weight-loss medicine who reports side effects takes them to the prescriber. Weight a client is losing without meaning to, or a client who is eating very little, is a reason to involve a clinician.

Some patterns call for a closer look at the eating itself: filling up on vegetables to avoid eating anything else, distress about eating a food from the high group, weighing or calculating every meal long after it stopped being useful, turning down meals with others, or describing foods as good and bad. Many of these have ordinary reasons, from a dietitian's plan to a work schedule to a household's preferences, so on its own a behavior tells a coach little, and none of this is a diagnosis. The coach asks what the behavior is for, whether it causes distress, whether it is narrowing what the person eats, and whether it is getting in the way of daily life. Where the answers raise a real concern about disordered eating, the coach follows their own referral process, or brings the concern to the client's clinician under an existing care plan.

Special populations

Pregnancy and breastfeeding

The searches for this page did not identify a study of the Volumetrics plan in pregnancy or breastfeeding. The workplace trial of the plan excluded people who were pregnant or planning pregnancy (Lowe et al., 2010), as did the 12-week trial that used the name (Cloos et al., 2025). In one cohort of 1,231 pregnant women, those whose diets were in the second and third quarters of energy density gained more weight than those in the lowest quarter, by 0.91 and 1.47 kilograms (Deierlein et al., 2008); that is an association, not a test of the plan. U.S. News lists pregnant women among those who should not follow the diet (Schueller, 2026). Any eating plan in pregnancy or breastfeeding belongs with the obstetric clinician and a registered dietitian.

Children and adolescents

The searches did not identify a study of the named plan in children or teenagers. Energy density research in children exists: in feeding studies in preschool children, lowering the energy density of meals or hiding pureed vegetables in entrees lowered calories eaten and raised vegetable intake over a day or 2 (Leahy et al., 2008; Spill et al., 2011). Those were short studies in childcare settings, read here in abstract only, not a weight-loss diet. U.S. News lists children among those who should not follow the diet (Schueller, 2026). A coach works with the adult in front of them; a child's eating belongs to the family and the pediatric clinician.

Older adults

The searches did not identify a study of the plan designed for older adults. In a survey of 2,244 adults over 65 in Spain, read in abstract only, lower-energy-density diets went with better intakes of fiber, several vitamins, calcium and magnesium (Schröder et al., 2008). The other side matters too: when the energy density of home-delivered lunches for older adults at nutrition risk was raised, their intake rose by 453 calories a day (Silver et al., 2008). An older adult who eats little, has a small appetite or is losing weight without meaning to may need more energy in each bite, not less, and is a client for the physician and a dietitian before a lower-calorie plan.

Athletes and people with high activity

The searches did not identify a study of the plan in athletes. In 25 female endurance athletes, read in abstract only, those with low energy availability or loss of menstrual periods ate diets lower in energy density and fat, and the authors named low energy density and high fiber as dietary concerns (Melin et al., 2016). A 12-week trial in physically active middle-aged adults found that lean mass, measured by bioelectrical impedance, held steady while fat mass fell, both with a rule-based low-energy-density diet and with an eating window (Cloos et al., 2025). Whether a plan meets the energy and protein needs of training is a question for a sports dietitian.

People taking medication for diabetes, blood pressure, or blood thinning

Insulin, sulfonylureas and meglitinides can cause low blood sugar, and eating fewer carbohydrates or skipping or delaying meals makes it more likely (National Institute of Diabetes and Digestive and Kidney Diseases, n.d.-b). People taking warfarin need a consistent intake of vitamin K, and sudden changes can increase or decrease its effect (National Institutes of Health Office of Dietary Supplements, 2021); a plan built on vegetables can add many leafy greens quickly. The standing rule is that the client keeps the prescriber informed before a substantial change in eating, rather than asking permission for every food choice.

People with a history of disordered eating

The searches did not identify a study measuring the onset or worsening of disordered eating in people following the plan. The 12-week trial that used the name excluded people with eating disorders (Cloos et al., 2025), the year-long energy density trial excluded people with symptoms of disordered eating (Ello-Martin et al., 2007), and the 2 trials that handed out a book did not report outcomes for people with these histories.

Two kinds of research bear on this group. In women recently weight-restored after treatment for anorexia nervosa, lower energy density of the diet predicted a poorer outcome in the following year, in 47 women and again in a replication in 16 (Schebendach et al., 2008, 2012); the 2008 paper was read in abstract only, and a 2012 correction to it is indexed but was not read for this page. In adults with binge eating disorder, adding low-energy-density counseling to cognitive behavioral therapy did not change binge remission (Masheb et al., 2011), and an online program that included content adapted from a Volumetrics book did not change eating disorder symptoms compared with the therapy content alone (Grammer et al., 2023).

U.S. News lists people with current or past eating disorders among those who should not follow the diet (Schueller, 2026). A client with this history is referred to their clinician, or through the coach’s own referral process if they have none, before the plan is discussed further.

Client misconceptions

Three come up most. The first is that research has proven the Volumetrics Diet works. Research has shown that people served lower-energy-density food eat fewer calories in the short term, but the named plan has been tested in only a few trials, with mixed results and low to very low certainty (Lowe et al., 2010; Lowe et al., 2014). The second is that eating more vegetables will by itself cause weight loss. A review of trials found no discernible effect on weight from advice or provision to eat more fruit and vegetables without reducing other foods (Kaiser et al., 2014); the plan's own logic depends on replacing energy-dense foods, not adding to them.

The third is that foods in the high group are bad foods. The groups describe calories per gram, not nutritional value: nuts and cooking oils sit in the highest group, and the American Heart Association lists unsaturated fats in place of saturated fats among the features of a heart-healthy pattern (Lichtenstein et al., 2026). Each myth is taken up in section 6.

🤝 COACHING CONNECTION

Rachel tells her coach she has read a Volumetrics book and wants to "eat as much as I want as long as it's vegetables" so she never feels hungry again. The coach reflects how tired she sounds of being hungry and asks what hunger has been like for her on past diets. Rachel says she usually ends up eating a lot at night. With her permission, the coach shares that the research behind the book is mostly about swapping some energy-dense foods for water-rich ones, not adding vegetables on top. Rachel decides to start with soup or salad before dinner on weeknights and to notice how hungry she is at 9 p.m. The coach asks how she will keep track of that in a way that feels useful rather than like another diet rule.

4. The evidence

(select the heading to open or close this section)

This section keeps 2 bodies of research apart. Research on the Volumetrics plan as published means studies that gave participants a Volumetrics book or content taken from one, or that tested a diet under the Volumetrics name. Research on energy density means studies of lower-energy-density foods or diets in general, whatever they were called; it is the science the books draw on, and no other archive page carries it, so this page reports it here, labeled as research on energy density rather than on the named plan.

The searches for this page, run on October 19, 2026 in Europe PMC, which indexes PubMed, and in ClinicalTrials.gov, identified 2 randomized trials that gave participants a Volumetrics book, one randomized trial whose program included content adapted from one, and one randomized trial of a diet labeled volumetrics whose rules did not come from the books. A 2017 systematic review that searched for trials of 20 popular diets by name, Volumetrics among them, found eligible trials for 7 of the 20, and Volumetrics was not one of the 7 (Anton et al., 2017).

A 2020 network review labeled the year-long energy density trial described below Volumetrics and published certainty ratings for it (Ge et al., 2020). That trial used some book-linked portion guidance but did not test the book as a program, so this page treats it as research on energy density, carries the review's rating exactly in its own row, and does not transfer it to the book-maintenance comparison in the banner. The certainty ratings are in the Evidence rating and review record at the end of the page.

Evidence from randomized controlled trials

A trial assigns people to a diet by chance and compares them with people assigned to something else, which is the strongest way to test whether the diet itself causes a result. This archive reports body weight as something a study measured, in that study's own numbers, and not as a goal or as a measure of whether a diet worked; see the standing rule in the review record at the foot of this page.

Trials of the Volumetrics plan as published

The longest test of the book comes from a primary care trial in Philadelphia. Of 238 adults referred by their doctors, 132 completed a 12-week weight-loss phase that used meal replacement shakes and bars, losing 6.1 kilograms on average, and were then randomly assigned to 4 maintenance groups for 9 months: lifestyle modification alone, continued meal replacements, an energy density program, or both. The energy density program gave participants the first Volumetrics book with lessons that complemented it, homework on buying and cooking lower-energy-density foods, and advice to start meals with a food such as broth-based soup (Lowe et al., 2014). Treatment was delivered by telephone, and weight was measured at clinic visits.

At the follow-ups 1 and 2 years after treatment ended, the group that received the energy density program without meal replacements had regained less weight than the lifestyle-only group: 0.41 against 3.20 kilograms at the first follow-up and 0.52 against 5.06 kilograms at the second, measured from the start of maintenance. The other 2 groups did not differ significantly from the lifestyle-only group, and the group that received the same energy density program together with meal replacements regained 2.70 and 4.55 kilograms. About a third of participants missed each follow-up visit, and diet recalls showed no difference between groups in energy density or calories, so the authors could not identify what produced the result and called for replication (Lowe et al., 2014).

That trial was funded by the National Institutes of Health; the meal replacements were provided at cost by their maker, and the senior author declared that he sat on a scientific advisory committee for Weight Watchers International (Lowe et al., 2014). Rolls was not an author. The page rates this comparison in its review record: low certainty, from one trial with missing follow-up data and a wide interval. The group that received the book together with meal replacements did not show the same advantage, so the result should not be generalized across packages.

A workplace study at 2 Philadelphia hospitals tested the book as prevention rather than treatment. Ninety-six employees who regularly ate lunch in the hospital cafeteria were randomly assigned either to cafeteria changes alone, new lower-energy-density menu items and labels showing each food's energy density group, or to the same changes plus 4 group classes based on the first Volumetrics book, a copy of the book and discounts on low-energy-density foods (Lowe et al., 2010). Lunch calories fell in both groups, but no difference between groups was detected in calories, in diet recalls or in measured weight, at the end of the 3-month intervention or 12 months after it ended.

By 12 months 42.7 percent had dropped out, significantly more from the group that received the book (Lowe et al., 2010). Rolls was a co-author of that paper; its conflict of interest statement lists ties only for the first author and says the other authors declared none (Lowe et al., 2010), while Rolls's later papers declare that she receives royalties from the books (Rolls, 2017).

Two other trials used the name or the content in different ways. An online program for 60 young adults with binge-type eating disorders and high body weight added behavioral weight-loss content, including energy density lessons adapted from The Ultimate Volumetrics Diet, to cognitive behavioral therapy tools, and compared it over 8 weeks with the therapy tools alone; neither eating disorder symptoms nor self-reported weight differed between groups, and both groups had fewer binge episodes (Grammer et al., 2023). A German trial in 37 physically active adults who completed it called its intervention a volumetrics diet, defined as keeping every meal at or below 1.5 calories per gram with no caloric drinks, drawn from German nutrition society guidance rather than from Rolls's books; it is described under Head to head below (Cloos et al., 2025).

Energy density trials: body weight, as measured

The rest of this section is research on energy density in general, not on the named plan. The central weight-loss trial is from Rolls's laboratory. Ninety-seven women with obesity were randomly assigned to dietitian counseling either to reduce fat or to reduce fat and eat more water-rich foods, especially fruit and vegetables, for 1 year, with no calorie or fat limits; both groups were taught about portion sizes, and counseling time was matched (Ello-Martin et al., 2007). Seventy-one women completed the year. Among completers, the added-produce group had lost 8.9 kilograms at 6 months against 6.7 kilograms in the fat-reduction group, and 7.9 against 6.4 kilograms at 12 months. The pattern of weight loss over the year differed between groups, both in completers and in all 97 randomized women.

The added-produce group also ate a greater weight of food and reported less hunger (Ello-Martin et al., 2007). The trial was funded by the National Institutes of Health, and the authors declared no conflicts of interest. It was read here in the published version. The water-rich food group was encouraged to eat larger portions of low-energy-density foods and recommended servings of energy-dense ones, guidance the paper credits to the first Volumetrics book, but participants were not given the book as a program. The trial's significant tests concern the pattern of weight change across the year. This page's own approximation from the published means and standard errors puts the 12-month difference between completer groups at about 1.5 kilograms, with an interval from about minus 1 to 4 kilograms, which includes no difference, and the review record rates it low.

Other trials point in more than one direction, and most were read in abstract only. In a 1-year trial in 200 adults on an energy-restricted diet, eating 2 servings a day of a low-energy-density soup produced more weight loss than eating the same calories as high-energy-density snacks, 7.2 against 4.8 kilograms, though a group given no special food lost 8.1 kilograms (Rolls et al., 2005). In 103 women who had lost weight with meal replacements, adding a reduced energy density eating program to a maintenance program lowered the energy density of their diets but did not improve maintenance (Lowe et al., 2008). In 70 Iranian adults who had recently lost weight, a low-energy-density diet over 7 months was followed by a small weight change, minus 0.3 percent, against a 1.3 percent gain on a usual diet (Karimi et al., 2016).

Within large trials designed for other purposes, lowering energy density did not always change weight for long. In a multicomponent diet trial in 2,718 breast cancer survivors, read in abstract only, the intervention group lowered the energy density of their diets and kept it lower for 4 years, but the small weight difference at 1 year had disappeared by 4 years (Saquib et al., 2008); because the diet changed several things at once, this does not isolate energy density. A 2014 review, read in abstract only, of trials that told people to eat more fruit and vegetables, or provided them, without asking them to cut other foods found no discernible effect on weight (Kaiser et al., 2014). These results fit the plan's own logic, which depends on replacing energy-dense foods rather than adding to them, although the 2014 review tested adding foods, not replacing them.

A 2012 systematic review prepared for the 2010 Dietary Guidelines Advisory Committee, read in abstract only, included 7 randomized trials, 1 nonrandomized trial and 9 cohort studies in adults, and reported the committee's conclusion of strong and consistent evidence that dietary patterns relatively low in energy density improve weight loss and weight maintenance in adults (Pérez-Escamilla et al., 2012). That is the committee's grade, from its own grading method, not a GRADE rating, and this page does not carry it into its own table because only the abstract was read.

Energy density trials: energy intake and hunger

The strongest and most consistent findings concern how much people eat in the short term. A 2022 meta-analysis pooled 31 controlled studies, 27 in adults and 4 in children, each lasting 1 to 14 days, in which the same people were served food at higher and lower energy densities. Serving lower-energy-density food lowered daily energy intake by a large amount, a standardized mean difference of about 1.0, and people ate little more at other meals to make up for it (Robinson et al., 2022). Results varied widely in size between studies, though nearly all pointed the same way, and a test for publication bias was positive.

A 2023 meta-analysis of 38 randomized studies under controlled conditions found that meals of lower energy density, a median of 1.1 calories per gram, led people to eat about 223 fewer calories than meals of higher energy density, a median of 1.5, while the weight of food eaten did not change (Klos et al., 2023). In one 2-day study in 24 women, read in abstract only, serving every food at 75 percent of its usual energy density lowered intake by about 575 calories a day, and serving 75 percent of the usual portion lowered it by about 231, without changes in rated hunger or fullness (Rolls et al., 2006). These are short studies in which food was served to people, not trials of people choosing food for themselves.

Five of the studies in the 2022 meta-analysis also weighed people before and after, and the pooled weight change was about 0.7 kilograms more weight lost on the lower-energy-density food, with an interval that included no difference (Robinson et al., 2022). The paper gives that interval as minus 1.43 to 0.04 kilograms in its results and as minus 1.34 to 0.04 in its abstract; this page uses the results section.

Cardiometabolic outcomes

The searches did not identify a trial of the named plan or of an energy density diet that measured heart attacks, strokes or other cardiovascular events. Blood lipids were measured in the 2 trials of the book. In the primary care trial, total and LDL cholesterol rose less in the 2 groups that received the energy density program than in the other 2, an effect that was no longer significant once weight change was taken into account; blood pressure, triglycerides and HbA1c showed no effect of group (Lowe et al., 2014).

In the workplace trial, total cholesterol rose in the group that received the book and fell in the comparison group, largely because HDL cholesterol rose, and the authors said it was unclear whether the change was good or bad (Lowe et al., 2010). In the year-long energy density trial, the authors reported that weight loss led to favorable changes in blood lipids and insulin in both groups (Ello-Martin et al., 2007).

Cancer

The searches did not identify a randomized trial of the plan or of an energy density diet with cancer incidence or cancer outcomes as an outcome. The breast cancer survivor trial described above was a trial of a diet in people who already had cancer, and the analysis read here reported energy density and weight, not cancer outcomes (Saquib et al., 2008).

Body weight, as measured

The weight results from trials are reported above, separately for the named plan and for energy density research, because they answer different questions. For the named plan, the evidence is the 2 trials that handed out a book, one showing less regain in one of its 2 book groups and one showing no difference in weight; for energy density approaches, the year-long trial and several smaller or shorter trials, with mixed results beyond the first months.

Mortality

The searches did not identify a randomized trial of the plan or of an energy density diet that reported death from any cause or from a specific cause.

Eating behavior and wellbeing

Three trials measured eating behavior. In adults with binge eating disorder and obesity, 50 were randomly assigned to 6 months of cognitive behavioral therapy plus low-energy-density diet counseling or plus general nutrition counseling; binge remission did not differ, 52 against 44 percent of all randomized participants when those who left were counted as not remitted, and weight loss did not differ significantly, although the low-energy-density group lowered the energy density of its diet and ate more fruit and vegetables (Masheb et al., 2011). Rolls was a co-author of that trial, and its authors declared no conflicts of interest.

In the online trial in young adults with binge-type eating disorders, adding behavioral weight-loss content with Volumetrics-derived lessons did not change eating disorder attitudes or behaviors compared with therapy tools alone over 8 weeks; both groups improved, and fewer than half completed the program (Grammer et al., 2023). In the workplace trial, dietary restraint, the effort people put into limiting what they eat, rose during the intervention period in both groups, mostly in its rigid form, and then leveled off (Lowe et al., 2010). None of these studies measured the onset of an eating disorder.

Evidence from long-term prospective cohort studies

A cohort study follows people who already eat a certain way and records what happens to them. It can show that a pattern goes with an outcome; it cannot by itself show that the pattern caused it. The searches did not identify a cohort study of people following the Volumetrics plan. The cohorts below measured the energy density of people's usual diets from food questionnaires or recalls, so they are research on energy density, and different studies calculated it differently, some counting drinks and some counting only food.

Cardiometabolic outcomes

Three large cohorts examined energy density and new cases of type 2 diabetes, and they disagree. In 21,919 adults in Norfolk, England, followed for 12 years, those in the highest fifth of energy density, calculated from foods and drinks, had 60 percent higher odds of developing diabetes than those in the lowest fifth, an odds ratio of 1.60, from 1.19 to 2.16 (Wang et al., 2008). In a case-cohort study in 8 European countries with 12,403 new cases, energy density of foods alone was not associated with diabetes, a hazard ratio of 1.02 per 1 calorie per gram, from 0.93 to 1.13 (InterAct Consortium et al., 2013).

In 143,204 postmenopausal women in the United States followed for about 13 years, those in the highest fifth of energy density, counting foods only, had a 24 percent higher risk, a hazard ratio of 1.24, from 1.17 to 1.32 (Hingle et al., 2017). In the last study, the authors report that body mass index and waist size mediated the association.

Cancer

In 92,295 postmenopausal women in the Women's Health Initiative, those in the highest fifth of dietary energy density had about a 10 percent higher risk of any cancer linked to obesity than those in the lowest fifth, a subhazard ratio of 1.1, from 1.03 to 1.2, and the higher risk appeared limited to women who were of normal weight at enrollment (Thomson et al., 2018). For breast cancer alone, the same study found the highest fifth not clearly different from the lowest, a subhazard ratio of 1.06, from 0.97 to 1.1 as the paper rounds it.

In 56,795 postmenopausal women in the Cancer Prevention Study II Nutrition Cohort, read in abstract only, the highest fifth had a 20 percent higher rate of breast cancer, a rate ratio of 1.20, from 1.05 to 1.36 (Hartman et al., 2016). A Canadian case-cohort study did not detect clear associations with breast, endometrial, ovarian or colorectal cancer; its precision and definitions need to be considered alongside the positive cohorts (Arthur et al., 2018). It was read in abstract only, which gives no estimates. All are associations measured once by questionnaire, and the review record rates any obesity-related cancer and breast cancer as separate outcomes.

Body weight, as measured

The cohort studies of weight disagree too. Among 50,026 younger and middle-aged women in the Nurses' Health Study II, those whose diets rose most in energy density over 8 years gained more weight than those whose diets fell most, 6.42 against 4.57 kilograms after adjustment (Bes-Rastrollo et al., 2008). In 186 women followed for 6 years, a higher energy density went with greater weight gain (Savage et al., 2008). In 89,432 adults in 5 European countries followed for an average of 6.5 years, energy density was not associated with weight change, about 42 grams a year less per 1 calorie per gram, from 112 grams less to 28 grams more, but was weakly associated with a gain in waist size (Du et al., 2009).

A 2016 meta-analysis of observational studies, read in abstract only, reported that people in the highest group of energy density gained 2.26 kilograms more than those in the lowest, from 1.00 to 3.53 (Rouhani et al., 2016). In children, a meta-analysis of 6 cohort studies found a small association between energy density and gain in body fat, which became more uncertain once the authors adjusted for each study's biases, a correlation of 0.17 with an interval from minus 0.11 to 0.45 (Wilks et al., 2011).

Mortality

The searches did not identify a mortality study of the named Volumetrics plan. Research on dietary energy density is a different matter: a 2026 UK Biobank cohort analysis reported an association with all-cause mortality (Wang et al., 2026). In 208,312 adults followed for a median of 16.8 years, each 1 kilojoule per gram higher energy density, about a quarter of a calorie per gram, went with a 1.7 percent higher risk of death, a hazard ratio of 1.017, from 1.004 to 1.030. When the authors also adjusted for overall diet quality, the association was no longer seen, 0.983, from 0.965 to 1.001. Energy density was one of 63 nutrients tested, and the paper does not say whether drinks were counted. That observational association does not show that following the book, or changing energy density itself, changes survival.

Highlighted studies

These 5 studies carry the most weight on this page, the first 3 for the named plan and the last 2 for energy density research. Each is described so that a reader can judge it without opening the paper.

On a narrow screen, scroll the table sideways to see every column.

Highlighted studies for the Volumetrics Diet

Study	Design	Sample size	Duration	Finding	The limitation that matters
Lowe et al., 2014	Randomized trial of maintenance programs, 2 by 2 design; one arm received the Volumetrics book and energy density lessons	238 began; 132 who completed a 12-week weight-loss phase were randomized, 33 to the book arm and 33 to lifestyle alone	9 months of maintenance, then follow-up to 36 months from the start	Book arm regained 0.52 kilograms by the last follow-up against 5.06 in the lifestyle arm	The other arm given the book, with meal replacements, regained 4.55 kilograms; about a third missed each follow-up; no measured diet change explained the result
Lowe et al., 2010	Randomized trial at 2 hospital cafeterias; book, classes and discounts added to cafeteria changes	96 employees	3 months of intervention, follow-up to 12 months	No difference between groups detected in lunch calories, diet recalls or measured weight	42.7 percent had dropped out by 12 months, more in the book group; a prevention study, not a weight-loss trial
Cloos et al., 2025	Randomized trial; a rule labeled volumetrics diet, every meal at or below 1.5 calories per gram, against an 8-hour eating window	48 began; 37 completed, 21 and 16	12 weeks	Both groups lost about 1.6 to 1.8 kilograms and some body fat, with no difference detected between groups; adherence was lower with the energy density rule	The rule came from German nutrition societies, not Rolls's books; small, completers only; no between-group interval reported
Ello-Martin et al., 2007	Randomized trial of 2 dietitian-counseled energy density strategies	97 women with obesity; 71 completed	1 year	Adding water-rich foods to fat reduction gave more weight loss at 6 months, 8.9 against 6.7 kilograms; at 12 months, 7.9 against 6.4	The comparison group also lowered energy density; 27 percent did not finish; the 12-month difference is uncertain
Robinson et al., 2022	Meta-analysis of controlled feeding studies of served food at 2 or more energy densities	31 studies, 27 in adults and 4 in children	1 to 14 days	Lower energy density lowered daily energy intake by a large amount, a standardized mean difference of about 1.0	Short studies of served food in controlled settings; results varied in size; possible publication bias

Head to head

One trial compared a diet under the Volumetrics name with another named approach. In the German trial, physically active adults aged 30 to 65 were randomly assigned for 12 weeks either to keep every meal at or below 1.5 calories per gram, with no caloric drinks, or to eat within an 8-hour window from 11:30 a.m. to 7:30 p.m. Of 48 who began, 37 completed: 21 in the energy density group and 16 in the window group (Cloos et al., 2025). Both groups lost weight and body fat, measured by bioelectrical impedance, by similar amounts; the energy density group went from 73.59 to 71.97 kilograms and the window group from 78.99 to 77.23, and no difference between groups was detected.

Reported adherence was lower in the energy density group, and the study had no outside funding (Cloos et al., 2025). Its rule was drawn from German nutrition societies' energy density guidance and did not cite Rolls's books, so it tested a rule that shares the plan's central idea rather than the plan as published. The eating-window approach is described on the Intermittent Fasting page; Time-Restricted Eating is the related daily-window approach.

The other comparisons found by these searches involve energy density counseling rather than the named plan. In a 12-week study within weekly Weight Watchers group meetings, adults counseled on a low-energy-density plan, a low-glycemic-index plan or the program's own points-based portion-control plan lost similar amounts of weight and showed similar changes in metabolic measures (Melanson et al., 2012). The paper describes the portion-control group in one place as a similar group who had enrolled in that plan and in another as randomized, and one author declared consulting fees and research grants from Weight Watchers International. The WeightWatchers page describes that program's own trials.

In the primary care trial, the energy density program was compared directly with continued meal replacements during maintenance, and only the energy density program without meal replacements differed from the lifestyle-only group (Lowe et al., 2014); the Meal Replacement Programs page covers meal replacement evidence. The searches did not identify a trial comparing the Volumetrics plan with the Mayo Clinic Diet, Noom, the Mediterranean Diet or the DASH Diet.

Where the evidence is absent

The searches for this page, run on October 19, 2026 in Europe PMC and ClinicalTrials.gov, including a separate search for each special population this archive covers, identified few trials of the Volumetrics plan as published: 2 that handed out a book, one that adapted its content, and one that used the name for a different rule. They did not identify a trial of the named plan as a stand-alone weight-loss treatment against usual care; a trial of the plan longer than 12 months of treatment; or any study of the plan measuring heart attacks, strokes, cancer, death, vitamin and mineral intake or status, or the onset of disordered eating.

For energy density research in general, they did not identify a randomized trial with cardiovascular events, cancer or death as outcomes; the one cohort analysis of energy density and death they found is described above. They did not identify a study of the named plan in pregnancy, breastfeeding, children, adolescents, older adults as a group, athletes, people taking diabetes, blood pressure or weight-loss medicines, or people with kidney disease, nor a study of what the plan costs at the store or of its environmental footprint. The books themselves were not opened. The studies reviewed for this page do not establish that the plan has the effects claimed for it, and they do not establish that it lacks them. These searches were not an exhaustive check of every database, regulator, court or special population.

5. Mechanisms

(optional reading; select the heading to open or close this section)

This section explains how the diet is thought to work in the body. You can skip it. Nothing in the coaching sections depends on it.

Established mechanisms

Energy density depends mostly on 3 things in a food: water, which adds weight but no calories; fat, which carries 9 calories per gram; and carbohydrate and protein, which carry 4 (Rolls, 2009, 2017). Raising the proportion of water or water-rich ingredients, such as vegetables, fruit or broth, lowers a food's energy density, and so does lowering its fat. In controlled studies, lowering the calorie density of foods, for example by adding water-rich vegetables and fruit, increased fullness and lowered how much people ate at a meal, because people tend to eat a fairly consistent weight of food; the reasons for that tendency are not yet well understood (Rolls, 2009). The pooled studies in section 4 measured this directly: lower-energy-density meals led to fewer calories eaten with no change in the weight of food eaten (Klos et al., 2023).

Any change in body weight on the plan is expected to come from eating fewer calories than the body uses, not from a particular food. Rolls herself is quoted saying there is no way around that, only ways to make it less hungry work (Penn State News, 2012). That is also why adding vegetables without replacing anything else did not change weight in the trials pooled in 2014 (Kaiser et al., 2014). Water drunk with a meal does not act like water inside food: in Rolls's review, a soup made from a casserole and water was more filling than the same casserole served with a glass of the same water (Rolls, 2009).

Proposed mechanisms

Why a larger volume of food is more filling is less settled. Rolls's 2017 review describes a complex interplay of cognitive, sensory, gastrointestinal, hormonal and neural influences (Rolls, 2017), and her 2009 review names people's beliefs about how filling different foods are among the cognitive factors involved (Rolls, 2009). These are proposals from a body of mostly short studies. A proposed mechanism never supports a claim in section 4.

A second proposal places energy density among several food properties that drive intake. A 2025 review by Rolls's group proposes 3 established determinants, portion size, energy density and variety, and argues that energy density likely plays the most dominant role and that large portions of low-energy-density foods can be used to moderate intake (Rolls et al., 2025). That is the authors' proposal, and how these properties interact in everyday eating is still a research question.

6. Risks, contraindications and myths

(select the heading to open or close this section)

Warnings from professional or regulatory bodies

The searches for this page did not identify a warning about the Volumetrics plan from a professional or regulatory body; they covered Europe PMC and ClinicalTrials.gov and did not cover every regulator, state attorney general or court. A federal guide to choosing a weight-loss program lists promises to look out for, including "Lose weight while eating as much as you want of all your favorite foods!" (National Institute of Diabetes and Digestive and Kidney Diseases, n.d.-a). That is a general caution, not a finding about this plan, but it is worth knowing because the plan is often summarized as eat more, weigh less, and a client may have heard it that way. The plan as Rolls describes it asks people to eat more of some foods and less of others, not as much as they want of everything.

Nutrient gaps

The plan removes no food group, and its emphasis on vegetables, fruit, legumes and whole grains raises fiber and several vitamins and minerals. In the Spanish survey of adults over 65, those with lower-energy-density diets more often met recommendations for fiber, vitamin C, vitamin E, several B vitamins, folate, calcium and magnesium (Schröder et al., 2008). The searches for this page did not identify a study measuring nutrient intake or status in people following the named plan.

Two gaps are possible depending on how the plan is followed. A diet built heavily on vegetables, fruit and soup and sparing of meat, dairy, nuts and oils can run short of energy and protein for someone with high needs, which is the concern raised in female endurance athletes (Melin et al., 2016). And a client who cuts most fats can cut the unsaturated fats in fish, nuts and oils that heart-health guidance encourages (Lichtenstein et al., 2026). A dietitian is the right person to check a plan for an older adult, an athlete, a person with a medical condition or anyone eating very little.

Who should not follow it without medical supervision

Anyone taking insulin, a sulfonylurea or a meglitinide, because eating less, or skipping or delaying meals, can bring on low blood sugar (National Institute of Diabetes and Digestive and Kidney Diseases, n.d.-b). Anyone taking warfarin, because a sudden change in vitamin K intake can change its effect (National Institutes of Health Office of Dietary Supplements, 2021). Anyone taking blood pressure medicine or a weight-loss medicine, who keeps the prescriber informed before a substantial change in eating and whose prescriber decides whether the medicine still fits as eating and weight change. Anyone with kidney disease, whose needs depend on the stage of disease, lab results and dialysis, with the kidney care team.

Anyone pregnant or breastfeeding, and any child or teenager, whom U.S. News also lists among those who should not follow the diet (Schueller, 2026). An older adult with a small appetite or unintended weight loss. An athlete with high energy needs. And anyone with a current or past eating disorder, for whom a low-energy-density diet has been linked to poorer outcomes after treatment for anorexia nervosa (Schebendach et al., 2008, 2012). The special populations list in section 3 is built from these cautions.

Medication interactions

A coach never adjusts medication. The point of listing these is to know when the client should talk with the prescriber before starting. Insulin, sulfonylureas and meglitinides can cause low blood sugar, and not eating enough carbohydrates, or skipping or delaying meals, makes it more likely (National Institute of Diabetes and Digestive and Kidney Diseases, n.d.-b); a lower-calorie plan changes exactly those things. Warfarin needs a consistent intake of vitamin K, and sudden changes in intake can increase or decrease its effect (National Institutes of Health Office of Dietary Supplements, 2021); a plan built on vegetables can add many leafy greens quickly. Blood pressure medicine and weight-loss medicines are managed by the prescriber as weight, blood pressure and eating change.

Signs it is going wrong

Physical signs include shakiness, sweating, dizziness or confusion in a client on diabetes medicine; dizziness or lightheadedness, especially on standing, in a client on blood pressure medicine; unusual tiredness, feeling cold, or missed periods; ongoing bloating or stomach pain; side effects from a weight-loss medicine; and weight the client is losing without meaning to. For possible low blood sugar, follow the immediate-response steps in Referral red flags: the client's own diabetes plan first, emergency help if symptoms are severe or the person cannot manage the episode under that plan, and the prescriber afterward. Other physical signs are reasons to involve a clinician, not diagnoses, and working out the cause is the clinician's job.

Eating behaviors are a separate matter. Filling up on vegetables to avoid eating other foods, distress after eating a food from the high group, calculating the energy density of every meal long after it stopped being useful, turning down meals with others, or talking about foods as good and bad can each come from ordinary reasons, such as a work schedule, food access, a cultural practice, a household's preferences or a dietitian's plan. The coach asks what the behavior is for, whether it causes distress, whether it narrows what the person eats, and whether it gets in the way of daily life. A real concern goes through the coach’s own referral process or the client's existing clinical plan. A behavior alone is never a diagnosis.

Myths and where they came from

Myth: "On Volumetrics you can eat as much as you want and still lose weight."

Where it came from: summaries of the plan that stress large portions and never going hungry, such as a U.S. News headline promising to eat more and weigh less (Schueller, 2026). What is true: the plan asks people to eat larger portions of low-energy-density foods and smaller portions of energy-dense ones, and Rolls is quoted saying that weight loss still requires eating fewer calories than the body burns (Penn State News, 2012). In the short studies, people ate fewer calories because the food carried fewer calories per bite, not because calories stopped counting (Klos et al., 2023).

Myth: "Just add more fruit and vegetables and the weight will come off."

Where it came from: a reasonable reading of the plan's emphasis on produce. What is true: trials that told people to eat more fruit and vegetables, or delivered them, without asking them to cut other foods found no discernible effect on weight (Kaiser et al., 2014). The energy density trials that changed weight did so by replacing energy-dense foods or lowering fat at the same time (Ello-Martin et al., 2007).

Myth: "High-energy-density foods are unhealthy foods."

Where it came from: the plan's sorting of foods into groups, which can sound like a ranking of good and bad. What is true: the groups describe calories per gram, not nutritional value. Nuts and cooking oils sit in the highest group, while heart-health guidance encourages unsaturated fats in place of saturated fats (Lichtenstein et al., 2026; Schueller, 2026). And an energy-dense diet is not always a cheap one, or a low-energy-density one an expensive one: it depends on how price is measured (Davis & Carlson, 2015; Lipsky, 2009).

Myth: "It's one of the top-ranked diets, so it must be proven."

Where it came from: U.S. News lists the Volumetrics Diet among its top expert-recommended diets overall and for weight loss (Burdeos, n.d.; Jones, n.d.). What is true: U.S. News's scores summarize how many of its panelists recommended a diet (Schueller, 2025). A rating is a summary of expert opinion, not a study, and the named plan's own trials are few and give low to very low certainty. The research on energy density itself is a separate and larger body of work.

7. Key terms

Energy density

The number of calories in a given weight of food, usually given in calories per gram; vegetables and fruit are low in energy density.

Volumetrics

The eating approach in Barbara Rolls's books, which builds meals mostly from foods low in energy density so that portions stay satisfying while calories fall.

Energy density groups

The plan's 4 groups of foods, from very low, under 0.6 calories per gram, through low and medium, to high, 4.0 calories per gram and above.

Water-rich food

A food whose weight is mostly water, such as most vegetables, fruit and broth-based soups, which lowers its energy density.

Satiety

The feeling of fullness that follows eating and delays the next meal.

Preload

A first course or snack eaten before a meal in a study, such as soup or salad, to see how it changes what is eaten afterward.

Energy intake

The total calories a person eats and drinks over a set period.

Weight maintenance

Keeping off weight that has been lost; in trials, usually measured as how much weight is regained.

Crossover study

A study in which the same people receive each condition in turn, so each person is compared with themselves.

Meta-analysis

A study that combines the results of several studies to give one pooled estimate.

Standardized mean difference

A way of expressing a difference between groups in units of the outcome's spread, so studies that measured an outcome differently can be pooled; about 0.2 is small and 0.8 or more is large.

Hazard ratio and odds ratio

Ways of comparing how often an outcome occurs in 2 groups; a value above 1 means it was more common in the first group.

Dietary restraint

The deliberate effort a person makes to limit what they eat, measured by questionnaire; rigid restraint is the all-or-nothing form.

Binge eating disorder

An eating disorder marked by repeated episodes of eating an unusually large amount of food with a sense of loss of control, without the compensating behaviors of bulimia nervosa.

Energy availability

The energy left for the body's functions after the energy used in exercise is subtracted from what is eaten; low energy availability is a concern in athletes.

Royalty

A payment an author receives from each sale of a book.

8. Review questions

1. What is energy density, what makes a food low or high in it, and how does the Volumetrics plan use energy density to shape a meal without forbidding any food?
2. Drawing on section 4: what did the primary care trial give participants in its energy density arm, what happened to weight in the 2 arms that received the book, and why does this page rate the result low? How does that evidence differ from the short controlled studies of energy density and energy intake?
3. A client who takes insulin tells you she has started filling half of every meal with vegetables and soup and has cut out bread and pasta. What happens first if she reports shakiness and sweating, what does she do before a substantial change in eating, and where is the referral line?
4. A client recovering from anorexia nervosa says a friend recommended Volumetrics. What does the research on energy density after treatment for anorexia nervosa suggest, and what does the coach do?
5. Drawing on sections 1 and 6: a client says the diet lets her eat as much as she wants. Where does that idea come from, and what do the plan's author and the controlled studies say?

9. References

Anton, S. D., Hida, A., Heekin, K., Sowalsky, K., Karabetian, C., Mutchie, H., Leeuwenburgh, C., Manini, T. M., & Barnett, T. E. (2017). Effects of popular diets without specific calorie targets on weight loss outcomes: Systematic review of findings from clinical trials. Nutrients, 9(8), Article 822. https://doi.org/10.3390/nu9080822

Arthur, R., Kirsh, V., & Rohan, T. E. (2018). Association between dietary energy density and risk of breast, endometrial, ovarian, and colorectal cancer among Canadian women. Cancer Epidemiology, Biomarkers & Prevention, 27(3), 338-341. https://doi.org/10.1158/1055-9965.EPI-17-0861

Bes-Rastrollo, M., van Dam, R. M., Martinez-Gonzalez, M. A., Li, T. Y., Sampson, L. L., & Hu, F. B. (2008). Prospective study of dietary energy density and weight gain in women. The American Journal of Clinical Nutrition, 88(3), 769-777. https://doi.org/10.1093/ajcn/88.3.769

Burdeos, J. (n.d.). Top expert-recommended diets overall. U.S. News & World Report. health.usnews.com/best-diet/best-diets-overall

Cloos, A., Geisler, S., & Isenmann, E. (2025). Similar body composition outcomes following volumetric diet and time-restricted eating in middle-aged individuals: A 12-week randomized controlled trial. Nutrition Journal, 24, Article 94. https://doi.org/10.1186/s12937-025-01167-9

Davis, G. C., & Carlson, A. (2015). The inverse relationship between food price and energy density: Is it spurious? Public Health Nutrition, 18(6), 1091-1097. https://doi.org/10.1017/S1368980014001098

Deierlein, A. L., Siega-Riz, A. M., & Herring, A. (2008). Dietary energy density but not glycemic load is associated with gestational weight gain. The American Journal of Clinical Nutrition, 88(3), 693-699. https://doi.org/10.1093/ajcn/88.3.693

Drewnowski, A., Rehm, C. D., Martin, A., Verger, E. O., Voinnesson, M., & Imbert, P. (2015). Energy and nutrient density of foods in relation to their carbon footprint. The American Journal of Clinical Nutrition, 101(1), 184-191. https://doi.org/10.3945/ajcn.114.092486

Du, H., van der A, D. L., Ginder, V., Jebb, S. A., Forouhi, N. G., Wareham, N. J., Halkjaer, J., Tjønneland, A., Overvad, K., Jakobsen, M. U., Buijsse, B., Steffen, A., Palli, D., Masala, G., Saris, W. H., Sørensen, T. I., & Feskens, E. J. (2009). Dietary energy density in relation to subsequent changes of weight and waist circumference in European men and women. PLOS ONE, 4(4), Article e5339. https://doi.org/10.1371/journal.pone.0005339

Ello-Martin, J. A., Roe, L. S., Ledikwe, J. H., Beach, A. M., & Rolls, B. J. (2007). Dietary energy density in the treatment of obesity: A year-long trial comparing 2 weight-loss diets. The American Journal of Clinical Nutrition, 85(6), 1465-1477. https://doi.org/10.1093/ajcn/85.6.1465

Ge, L., Sadeghirad, B., Ball, G. D. C., da Costa, B. R., Hitchcock, C. L., Svendrovski, A., Kiflen, R., Quadri, K., Kwon, H. Y., Karamouzian, M., Adams-Webber, T., Ahmed, W., Damanhoury, S., Zeraatkar, D., Nikolakopoulou, A., Tsuyuki, R. T., Tian, J., Yang, K., Guyatt, G. H., & Johnston, B. C. (2020). Comparison of dietary macronutrient patterns of 14 popular named dietary programmes for weight and cardiovascular risk factor reduction in adults: Systematic review and network meta-analysis of randomised trials. BMJ, 369, Article m696. https://doi.org/10.1136/bmj.m696. A correction was published (BMJ, 370, Article m3095, https://doi.org/10.1136/bmj.m3095); it lists changes to the macronutrient-pattern estimates and Table 1, not to the named-diet tables used on this page.

Grammer, A. C., Monterubio, G. E., D'Adamo, L., Balantekin, K. N., Taylor, C. B., Fitzsimmons-Craft, E. E., & Wilfley, D. E. (2023). Evaluation of a combined, online intervention for binge-type eating disorders and high body weight in young adults. Eating Behaviors, 50, Article 101789. https://doi.org/10.1016/j.eatbeh.2023.101789

Hartman, T. J., Gapstur, S. M., Gaudet, M. M., Shah, R., Flanders, W. D., Wang, Y., & McCullough, M. L. (2016). Dietary energy density and postmenopausal breast cancer incidence in the Cancer Prevention Study II Nutrition Cohort. The Journal of Nutrition, 146(10), 2045-2050. https://doi.org/10.3945/jn.116.234344

Hingle, M. D., Wertheim, B. C., Neuhouser, M. L., Tinker, L. F., Howard, B. V., Johnson, K., Liu, S., Phillips, L. S., Qi, L., Sarto, G., Turner, T., Waring, M. E., & Thomson, C. A. (2017). Association between dietary energy density and incident type 2 diabetes in the Women's Health Initiative. Journal of the Academy of Nutrition and Dietetics, 117(5), 778-785.e1. https://doi.org/10.1016/j.jand.2016.11.010

InterAct Consortium, van den Berg, S. W., van der A, D. L., Spijkerman, A. M., van Woudenbergh, G. J., Tijhuis, M. J., Amiano, P., Ardanaz, E., Beulens, J. W., Boeing, H., Clavel-Chapelon, F., Crowe, F. L., de Lauzon-Guillain, B., Fagherazzi, G., Franks, P. W., Freisling, H., Gonzalez, C., Grioni, S., Halkjaer, J., . . . Wareham, N. J. (2013). The association between dietary energy density and type 2 diabetes in Europe: Results from the EPIC-InterAct Study. PLOS ONE, 8(5), Article e59947. https://doi.org/10.1371/journal.pone.0059947

Jones, L. (n.d.). Expert-recommended diets for weight loss. U.S. News & World Report. health.usnews.com/best-diet/best-weight-loss-diets

Kaiser, K. A., Brown, A. W., Bohan Brown, M. M., Shikany, J. M., Mattes, R. D., & Allison, D. B. (2014). Increased fruit and vegetable intake has no discernible effect on weight loss: A systematic review and meta-analysis. The American Journal of Clinical Nutrition, 100(2), 567-576. https://doi.org/10.3945/ajcn.114.090548

Karimi, G., Azadbakht, L., Haghighatdoost, F., & Esmaillzadeh, A. (2016). Low energy density diet, weight loss maintenance, and risk of cardiovascular disease following a recent weight reduction program: A randomized control trial. Journal of Research in Medical Sciences, 21, Article 32. https://doi.org/10.4103/1735-1995.181992

Klos, B., Cook, J., Crepaz, L., Weiland, A., Zipfel, S., & Mack, I. (2023). Impact of energy density on energy intake in children and adults: A systematic review and meta-analysis of randomized controlled trials. European Journal of Nutrition, 62(3), 1059-1076. https://doi.org/10.1007/s00394-022-03054-z

Leahy, K. E., Birch, L. L., & Rolls, B. J. (2008). Reducing the energy density of multiple meals decreases the energy intake of preschool-age children. The American Journal of Clinical Nutrition, 88(6), 1459-1468. https://doi.org/10.3945/ajcn.2008.26522

Lichtenstein, A. H., Khera, A., Anderson, C. A. M., Appel, L. J., DeSilva, D. M., Gardner, C., Hu, F. B., Jones, D. W., Petersen, K. S., & American Heart Association. (2026). 2026 dietary guidance to improve cardiovascular health: A scientific statement from the American Heart Association. Circulation, 153(18), e1285-e1295. https://doi.org/10.1161/CIR.0000000000001435

Lipsky, L. M. (2009). Are energy-dense foods really cheaper? Reexamining the relation between food price and energy density. The American Journal of Clinical Nutrition, 90(5), 1397-1401. https://doi.org/10.3945/ajcn.2008.27384

Lowe, M. R., Butryn, M. L., Thomas, J. G., & Coletta, M. (2014). Meal replacements, reduced energy density eating, and weight loss maintenance in primary care patients: A randomized controlled trial. Obesity, 22(1), 94-100. https://doi.org/10.1002/oby.20582

Lowe, M. R., Butryn, M. L., & Zhang, F. (2018). Evaluation of meal replacements and a home food environment intervention for long-term weight loss: A randomized controlled trial. The American Journal of Clinical Nutrition, 107(1), 12-19. https://doi.org/10.1093/ajcn/nqx005

Lowe, M. R., Tappe, K. A., Annunziato, R. A., Riddell, L. J., Coletta, M. C., Crerand, C. E., Didie, E. R., Ochner, C. N., & McKinney, S. (2008). The effect of training in reduced energy density eating and food self-monitoring accuracy on weight loss maintenance. Obesity, 16(9), 2016-2023. https://doi.org/10.1038/oby.2008.270

Lowe, M. R., Tappe, K. A., Butryn, M. L., Annunziato, R. A., Coletta, M. C., Ochner, C. N., & Rolls, B. J. (2010). An intervention study targeting energy and nutrient intake in worksite cafeterias. Eating Behaviors, 11(3), 144-151. https://doi.org/10.1016/j.eatbeh.2010.01.002

Masheb, R. M., Grilo, C. M., & Rolls, B. J. (2011). A randomized controlled trial for obesity and binge eating disorder: Low-energy-density dietary counseling and cognitive-behavioral therapy. Behaviour Research and Therapy, 49(12), 821-829. https://doi.org/10.1016/j.brat.2011.09.006

Masset, G., Vieux, F., Verger, E. O., Soler, L. G., Touazi, D., & Darmon, N. (2014). Reducing energy intake and energy density for a sustainable diet: A study based on self-selected diets in French adults. The American Journal of Clinical Nutrition, 99(6), 1460-1469. https://doi.org/10.3945/ajcn.113.077958

Melanson, K. J., Summers, A., Nguyen, V., Brosnahan, J., Lowndes, J., Angelopoulos, T. J., & Rippe, J. M. (2012). Body composition, dietary composition, and components of metabolic syndrome in overweight and obese adults after a 12-week trial on dietary treatments focused on portion control, energy density, or glycemic index. Nutrition Journal, 11, Article 57. https://doi.org/10.1186/1475-2891-11-57

Melin, A., Tornberg, Å. B., Skouby, S., Møller, S. S., Faber, J., Sundgot-Borgen, J., & Sjödin, A. (2016). Low-energy density and high fiber intake are dietary concerns in female endurance athletes. Scandinavian Journal of Medicine & Science in Sports, 26(9), 1060-1071. https://doi.org/10.1111/sms.12516

Monsivais, P., & Drewnowski, A. (2007). The rising cost of low-energy-density foods. Journal of the American Dietetic Association, 107(12), 2071-2076. https://doi.org/10.1016/j.jada.2007.09.009

National Institute of Diabetes and Digestive and Kidney Diseases. (n.d.-a). Choosing a safe & successful weight-loss program. niddk.nih.gov/health-information/weight-management/choosing-a-safe-successful-weight-loss-program

National Institute of Diabetes and Digestive and Kidney Diseases. (n.d.-b). Low blood glucose (hypoglycemia). niddk.nih.gov/health-information/diabetes/overview/preventing-problems/low-blood-glucose-hypoglycemia

National Institutes of Health Office of Dietary Supplements. (2021). Vitamin K: Fact sheet for health professionals. ods.od.nih.gov/factsheets/VitaminK-HealthProfessional

Noom Inc. (2021). Effects of online app weight loss programs on liver health in obese adults (Identifier NCT05015491) [Clinical trial registration]. ClinicalTrials.gov. clinicaltrials.gov/study/NCT05015491

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Open Library. (n.d.-d). The ultimate volumetrics diet. Internet Archive. openlibrary.org/works/OL20354586W

Penn State Extension. (n.d.). The Volumetrics weigh of life: Weight management plan. extension.psu.edu/the-volumetrics-weigh-of-life-weight-management-plan

Penn State News. (2012, March 28). Ultimate Volumetrics diet book helps people lose weight, manage hunger. The Pennsylvania State University. psu.edu/news/research/story/ultimate-volumetrics-diet-book-helps-people-lose-weight-manage-hunger

Penn State News. (2023, December 13). With the new year, establish new healthy habits with Volumetrics series. The Pennsylvania State University. psu.edu/news/agricultural-sciences/story/new-year-establish-new-healthy-habits-volumetrics-series

Pérez-Escamilla, R., Obbagy, J. E., Altman, J. M., Essery, E. V., McGrane, M. M., Wong, Y. P., Spahn, J. M., & Williams, C. L. (2012). Dietary energy density and body weight in adults and children: A systematic review. Journal of the Academy of Nutrition and Dietetics, 112(5), 671-684. https://doi.org/10.1016/j.jand.2012.01.020

Robinson, E., Khuttan, M., McFarland-Lesser, I., Patel, Z., & Jones, A. (2022). Calorie reformulation: A systematic review and meta-analysis examining the effect of manipulating food energy density on daily energy intake. International Journal of Behavioral Nutrition and Physical Activity, 19, Article 48. https://doi.org/10.1186/s12966-022-01287-z

Rolls, B. J. (2009). The relationship between dietary energy density and energy intake. Physiology & Behavior, 97(5), 609-615. https://doi.org/10.1016/j.physbeh.2009.03.011

Rolls, B. J. (2016). Creativity needs some serendipity: Reflections on a career in ingestive behavior. Physiology & Behavior, 162, 186-195. https://doi.org/10.1016/j.physbeh.2016.02.009

Rolls, B. J. (2017). Dietary energy density: Applying behavioural science to weight management. Nutrition Bulletin, 42(3), 246-253. https://doi.org/10.1111/nbu.12280

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Rolls, B. J., Roe, L. S., & Meengs, J. S. (2006). Reductions in portion size and energy density of foods are additive and lead to sustained decreases in energy intake. The American Journal of Clinical Nutrition, 83(1), 11-17. https://doi.org/10.1093/ajcn/83.1.11

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Evidence rating and review record

Each row identifies the method, source, outcome or recommendation, and comparison being rated. Ratings from different tools are not interchangeable. The source is either a named published review or this page's own judgment. The rating in the banner is for this diet's main claimed outcome or recommendation, and the banner names the tool that produced it. A high rating means the research is solid; it does not mean the diet is right for everyone, and it does not mean a coach should recommend it.

The rated outcomes on this page use GRADE, the same 4-level scale as the clinical guidelines you will meet in practice. High means further research is very unlikely to change the conclusion. Moderate means further research may change it. Low means further research is likely to change it. Very low means the conclusion is uncertain. GRADE rates each outcome separately, so a diet can be high for one outcome and very low for another. A row marked Not rated is an abstention, not a certainty level: where no study addresses a question, there is nothing to rate.

For the Volumetrics Diet, all rows but one are this page's own judgment. One row carries a published GRADE rating exactly as a 2020 network review published it, for a trial that review labeled Volumetrics (Ge et al., 2020); the searches did not identify a published review that rated the plan as published. Each row says whether it concerns the named plan or energy density research. Low means further research is likely to change the conclusion, and Very low means any effect the studies suggest is very uncertain; neither means the plan has been shown not to work. The banner reflects the first row.

On a narrow screen, scroll the table sideways to see every column.

Evidence ratings, their sources and reasons

Outcome	Certainty	Who rated it, and for which comparison	Why it is rated this way
Measured weight regained over 21 months after a 12-week weight-loss phase, the Volumetrics book with energy density lessons compared with lifestyle maintenance alone (the banner rating)	Low	GRADE, this page's own judgment, from one randomized trial (Lowe et al., 2014). Population: adults referred from primary care with a body mass index over 30, or over 27 with a related condition, who had completed a 12-week weight-loss phase with meal replacements; about 2 in 3 African American, 9 in 10 women. Intervention: 9 months of telephone maintenance with the first Volumetrics book, complementary lessons and homework, and no meal replacements; 33 adults. Comparison: the same maintenance program without the book or meal replacements; 33 adults. Outcome: weight change in kilograms from the start of maintenance, measured at clinic visits. Follow-up: to the visit 1 year after treatment ended, 21 months after the start of maintenance.	Randomized evidence starts at high. Risk of bias is serious, lowered 1 level, mainly for missing data: about a third of participants missed each follow-up visit and 20.5 percent contributed no follow-up data, which mixed models do not fully correct when missingness may depend on weight. The paper also does not describe how allocation was concealed, and it describes the timing of randomization in 2 ways, before the weight-loss phase with assignment hidden until that phase ended, and among the 132 who completed it. Weight was measured at clinic visits, so knowing the assignment is not by itself a route to bias in this outcome. Inconsistency cannot be assessed from one trial and is not a deduction. Indirectness is not serious for this named comparison. Applicability: the package that combined the book with meal replacements did not show the same advantage, regaining 2.70 kilograms against 3.20 in the comparison group, so the finding should not be generalized across packages. Imprecision is serious, lowered 1 level: the difference, 3.20 against 0.41 kilograms, or about 2.8 kilograms, has an interval this page approximates at 0.1 to 5.5 kilograms from the reported least-squares means and their standard errors of 0.89 and 1.03 kilograms. That interval includes differences below the 1-kilogram threshold this page uses for a meaningful difference in measured weight between programs as well as larger ones; it does not include more regain with the book. With 33 people per group, the width of the interval already reflects the small sample, so no second level is taken for it. Publication bias cannot be assessed; not lowered. No factor raises it. High minus 2 is Low.
Measured weight 12 months after a 3-month program ended, the Volumetrics book, 4 classes and discounts on low-energy-density foods added to cafeteria changes, compared with cafeteria changes alone	Very low, for no clear difference detected	GRADE, this page's own judgment, from one randomized trial (Lowe et al., 2010). Population: 96 hospital and university employees in Philadelphia who ate lunch in the cafeteria at least twice a week, average body mass index 29.7. Intervention: the cafeteria changes plus the book, 4 group classes based on it and price discounts; 47 adults. Comparison: new lower-energy-density menu items and energy density labels alone; 49 adults. Outcome: measured weight. Follow-up: 3 months of intervention, then visits 6 and 12 months after it ended; this is a 3-month program measured a year later, not a 12-month supported program.	Randomized evidence starts at high. Risk of bias is very serious, lowered 2 levels, for attrition: 42.7 percent had dropped out by the 12-month follow-up, and significantly more dropped out of the book group at every assessment, so the groups analyzed may differ from those randomized. Weight was measured, so the lack of blinding is not counted as a separate route to bias. Inconsistency cannot be assessed from one trial. Indirectness is not serious for this comparison, though it is a prevention study in people not seeking weight loss. Imprecision is serious, lowered 1 level: the paper reports no between-group interval for weight change, and this page cannot compute one, because the weight table gives unadjusted group means and standard deviations at each visit rather than change scores; the unadjusted means rose 1.5 kilograms in the comparison group and 0.8 in the book group. With about 55 people left at 12 months, a difference of 1 kilogram in either direction cannot be ruled out. That is a judgment, not a computed interval, so this domain stays provisional. Publication bias cannot be assessed. No factor raises it. High minus 3 is Very low. This is not evidence that the book has no effect.
Measured body weight at 12 weeks, a rule labeled volumetrics diet, every meal at or below 1.5 calories per gram with no caloric drinks, compared with an 8-hour eating window	Very low, for no clear difference detected	GRADE, this page's own judgment, from one randomized trial (Cloos et al., 2025). Population: physically active adults aged 30 to 65 with a body mass index of 18.5 to 34.9. Intervention: the energy density rule, drawn from German nutrition society guidance, not from Rolls's books; 21 completers. Comparison: eating only between 11:30 a.m. and 7:30 p.m.; 16 completers. Outcome: body weight measured on an impedance scale. Follow-up: 12 weeks.	Randomized evidence starts at high. Risk of bias is serious, lowered 1 level: 11 of 48 dropped out and only completers were analyzed, and the method of randomization is described only as based on sex, age and weight; the paper's baseline table also marks age and height as differing between groups. Inconsistency cannot be assessed from one trial. Indirectness is not serious for the rule as tested, but the row does not describe the plan in the books. Imprecision is very serious, lowered 2 levels: the paper gives no between-group interval for weight. The groups went from 73.59 to 71.97 kilograms and from 78.99 to 77.23, a difference in change of about 0.1 kilograms. This page's reconstruction, which assumes a correlation of 0.95 to 0.98 between each person's starting and final weight because the paper does not report one, gives an interval of about minus 2.6 to 2.9 kilograms at 0.95, or minus 1.7 to 2.0 at 0.98. Either version crosses the 1-kilogram threshold in both directions. Because the correlation is assumed, this precision judgment stays provisional. Publication bias cannot be assessed. No factor raises it. High minus 3 is Very low.
Measured body weight at 12 months, counseling to reduce fat and add water-rich foods compared with counseling to reduce fat alone (research on energy density, not the named plan)	Low, for an uncertain difference	GRADE, this page's own judgment, from one randomized trial read in the published version (Ello-Martin et al., 2007). Population: women aged 20 to 60 with a body mass index of 30 to 40, without symptoms of disordered eating; more than 9 in 10 White. Intervention: dietitian counseling to reduce fat and eat more water-rich foods; 48 randomized, 35 completed. Comparison: the same counseling time on reducing fat; 49 randomized, 36 completed. Neither group had calorie limits, and both lowered energy density. Outcome: measured weight. Follow-up: 12 months.	Randomized evidence starts at high. Risk of bias is serious, lowered 1 level: 27 percent did not complete the year, and the 12-month figures in the published Table 2 are for completers; in the analysis of all 97 randomized women, the 12-month estimates were smaller, 6.4 and 4.9 kilograms, with the same gap of 1.5. Participants and dietitians were not blinded, which matters less for a measured outcome when counseling time was matched. Inconsistency cannot be assessed from one trial. Indirectness is not serious for this comparison. Imprecision is serious, lowered 1 level: the 12-month difference between completers, 7.9 against 6.4 kilograms lost, or 1.5 kilograms, has an interval this page approximates at minus 1.0 to 4.0 kilograms from the published standard errors of 0.9 kilograms in each group, which crosses both no difference and the 1-kilogram threshold. The paper's significant tests, P = 0.002 in completers and 0.021 in all randomized women, are longitudinal tests of a different pattern of weight change across the year, not tests of this 12-month difference; the 6-month difference, 2.2 kilograms, was clearer. Publication bias cannot be assessed. No factor raises it. High minus 2 is Low.
Weight change at 6 months, the network node a 2020 review labeled Volumetrics, which is the water-rich food arm of the year-long energy density trial, compared with usual diet (published rating; energy density research, not the plan as published)	Moderate	GRADE, published by a network meta-analysis (Ge et al., 2020, Supplementary Tables S2, S29 and S35). Population: adults with overweight or obesity in randomized trials. Intervention: the node the review labeled Volumetrics, whose only trial is Ello-Martin et al. (2007), with 35 completers in that arm. Comparison: usual diet, reached only through indirect comparisons with other trials, because this trial compared 2 counseling approaches with each other. Outcome: weight change in kilograms. Follow-up: 6 months.	The review's network estimate is 5.95 kilograms more lost than with usual diet, with a credible interval from 1.97 to 9.98, rated Moderate. For the direct comparison with the trial's lower-fat arm, 2.20 kilograms, from 0.13 to 4.27, the review's rating was Low, with risk of bias and imprecision judged serious. This page carries the label exactly and does not transfer it: the trial used some portion guidance from the first Volumetrics book but did not give participants the book as a program, so this is not a rating for the plan as published, for the book-maintenance comparison in the banner, or for 12 months. A correction to the review lists changes to its macronutrient-pattern estimates and its Table 1, and none to these named-diet tables.
Daily energy intake over 1 to 14 days, food served at lower compared with higher energy density (research on energy density)	Low, for lower intake	GRADE, this page's own judgment, from the data of a meta-analysis (Robinson et al., 2022), with a second meta-analysis consistent with it (Klos et al., 2023). Population: adults, 27 studies, and children, 4 studies, in controlled settings. Intervention: food served at a lower energy density. Comparison: the same people served the foods at a higher energy density. Outcome: calories eaten in a day, measured by researchers or partly self-reported. Follow-up: 1 to 14 days.	Within-person experiments start at high. Risk of bias is serious, lowered 1 level: in 10 of 31 studies the order of conditions was not randomized or not reported, and 14 used some self-reported intake, which can misstate how much was eaten. Inconsistency is not lowered: effect sizes varied, with I squared of 92 percent, but nearly all effects pointed the same way, and the pooled effect changed little when outliers were removed. Indirectness is not serious for this question about served food, but these were not trials of people choosing their own food. Imprecision is not serious: the interval, a standardized mean difference of minus 0.75 to minus 1.27, lies well beyond 0.2, a small effect. Publication bias is suspected, lowered 1 level: the review's test for small-study effects was positive. No upgrade applied. High minus 2 is Low. The direction is consistent; the size may change.
Weight change over 8 years in U.S. women, the largest rise compared with the largest fall in the energy density of the usual diet (cohort research on energy density)	Very low	GRADE, this page's own judgment, from one cohort read in full (Bes-Rastrollo et al., 2008). Population: 50,026 younger and middle-aged U.S. women in the Nurses' Health Study II. Exposure: change in the energy density of foods eaten, drinks excluded, from food questionnaires in 1991, 1995 and 1999; the highest fifth of change, a median rise of 0.99 calories per gram. Comparison: the lowest fifth of change, a median change of minus 0.05 calories per gram. Outcome: self-reported weight change in kilograms. Follow-up: 8 years.	Observational evidence starts at low. Risk of bias is serious, lowered 1 level: diet and weight changed over the same years, so the study cannot show which came first, and weight was self-reported, although self-reports agreed closely with measured weight in a validation in the original Nurses' Health Study (correlation 0.97); confounding is already reflected in the starting level. Inconsistency cannot be assessed from one study. Indirectness is not serious for this population. Imprecision is not serious: the adjusted 8-year weight gains were 6.42 and 4.57 kilograms, each with a standard error of 0.07, a difference of 1.85 kilograms with an interval this page approximates at 1.66 to 2.04, which lies above the 1-kilogram threshold this page uses for weight. Publication bias cannot be assessed from one study. The gradient across the fifths is not used to raise the rating, because risk of bias is serious. Low minus 1 is Very low.
Weight change over about 6 years in adults, higher compared with lower energy density of the usual diet at the start (cohort research on energy density)	Very low, provisional	GRADE, this page's own judgment, from 2 cohorts read in full (Du et al., 2009; Savage et al., 2008), with a meta-analysis read in abstract only and not used for the grade (Rouhani et al., 2016). Population: 89,432 adults in 5 European countries, and 186 non-Hispanic White women in Pennsylvania. Exposure: energy density of foods eaten, drinks excluded, at the start, from food questionnaires in the European study and from three 24-hour recalls in the U.S. study. Comparison: per 1 calorie per gram higher in the European study; diets below 1.5 calories per gram compared with diets above 1.85 in the U.S. study. Outcome: weight change in kilograms, self-reported at follow-up in most European centers and measured in the U.S. study. Follow-up: an average of 6.5 years in Europe and 6 years in the U.S. study.	Observational evidence starts at low. Risk of bias is serious, lowered 1 level: follow-up weight was self-reported in most European centers, and the U.S. association remains open to confounding. The U.S. paper reports that its energy density association persisted after adjustment for initial BMI, dietary fiber and caloric beverage intake; the quoted 6.4 and 2.5 kilogram gains are descriptive group results, not a fully adjusted between-group treatment contrast. Inconsistency is unresolved for a common contrast. In Europe, each 1 calorie per gram higher at baseline was associated with 42 grams less weight gain per year, from 112 grams less to 28 grams more. Multiplying by the average 6.5-year follow-up gives approximately 0.27 kilograms less gain, from 0.73 less to 0.18 more, assuming that annual association applies over that duration. The U.S. high-versus-low-category gap was 3.9 kilograms over 6 years, but a valid interval for that gap has not been established here; baseline category counts are not substituted for follow-up denominators. The studies differ in contrast and adjustment, so these results alone do not establish interval-based inconsistency. Indirectness is not serious for the stated cohort question. Imprecision is unresolved across the contrasts: the European approximation excludes a 1-kilogram difference over its average follow-up, but no verified U.S. interval is available to compare with that boundary. Publication bias cannot be assessed from 2 studies. No upgrade is applied. Low minus 1 reaches Very low. The row remains provisional for the U.S. precision assessment and the comparison across studies.
New cases of type 2 diabetes over about 12 years, higher compared with lower energy density of the usual diet (cohort research on energy density)	Very low	GRADE, this page's own judgment, from 3 cohort studies read in full (Hingle et al., 2017; InterAct Consortium et al., 2013; Wang et al., 2008). Population: 21,919 adults in Norfolk, England; a case-cohort study in 8 European countries with 12,403 cases; and 143,204 postmenopausal U.S. women. Exposure: energy density of the usual diet from food questionnaires, counting foods and drinks other than water in the Norfolk study and foods only in the other 2. Comparison: the highest against the lowest fifth in the Norfolk and U.S. studies, and per 1 unit of energy density in the 8-country and Norfolk studies. Outcome: diagnosed type 2 diabetes. Follow-up: about 12 to 13 years.	Observational evidence starts at low. Risk of bias is not lowered further: confounding is reflected in the starting level, and the food questionnaires' weak measure of food weight is shared by all 3 studies. Inconsistency is serious, lowered 1 level, judged within comparable contrasts. Highest against lowest fifth: an odds ratio of 1.60, from 1.19 to 2.16, in Norfolk, counting drinks, and a hazard ratio of 1.24, from 1.17 to 1.32, in U.S. women, foods only; the 8-country study reports its fifths only as close to 1, without intervals. Per 1 calorie per gram, foods only: a hazard ratio of 1.02, from 0.93 to 1.13, in the 8 countries, where the authors note that 1 calorie per gram is about the distance from the lowest to the highest fifth. Within the foods-only definition, the 8-country interval lies entirely below the U.S. interval, so the disagreement is not only a matter of significance or of how energy density was calculated. The Norfolk per-unit estimate, an odds ratio of 1.21 per kilojoule per gram, from 1.06 to 1.38, counts drinks and is not compared directly. Indirectness is not serious. Imprecision is not lowered separately: against a 25 percent relative change in risk, a common GRADE rule of thumb for an appreciable effect, the U.S. and Norfolk intervals include both small and appreciable increases and the 8-country interval excludes an appreciable increase, but the main uncertainty is the disagreement already counted. Publication bias cannot be judged from 3 studies. No upgrade. Low minus 1 is Very low. In the U.S. study, body size mediated the association, so it may reflect weight rather than energy density itself.
Any obesity-related cancer over about 15 years, highest compared with lowest fifth of the energy density of the usual diet, postmenopausal U.S. women (cohort research on energy density)	Very low	GRADE, this page's own judgment, from one cohort read in full (Thomson et al., 2018). Population: 92,295 women in the Women's Health Initiative. Exposure: energy density of foods eaten, drinks excluded, from one food questionnaire at enrollment. Comparison: the lowest fifth. Outcome: any of 8 cancers the American Institute for Cancer Research links to obesity, with death treated as a competing risk. Follow-up: an average of 14.6 years.	Observational evidence starts at low. Risk of bias is serious, lowered 1 level: energy density came from one questionnaire at enrollment, which estimates food weight poorly and cannot capture later change, and the higher risk appeared only in women of normal weight at enrollment, while the authors note that under-reporting of intake is more likely in women with higher body weight. Inconsistency cannot be assessed from one study. Indirectness is not serious for postmenopausal women. Imprecision is not serious: the subhazard ratio, 1.1, from 1.03 to 1.2, excludes no association and excludes a 25 percent relative increase, a common GRADE rule of thumb for an appreciable effect. Publication bias cannot be judged from one study. No upgrade. Low minus 1 is Very low. This composite outcome is not combined with the breast cancer row below.
Breast cancer over about 12 to 15 years, highest compared with lowest fifth of the energy density of the usual diet, women (cohort research on energy density)	Very low, provisional	GRADE, this page's own judgment, from one cohort read in full (Thomson et al., 2018) and 2 read in abstract only (Arthur et al., 2018; Hartman et al., 2016). Population: 92,295 postmenopausal women in the Women's Health Initiative; 56,795 postmenopausal women in the Cancer Prevention Study II Nutrition Cohort; and a case-cohort study of Canadian women with 922 breast cancer cases. Exposure: energy density from a food questionnaire at enrollment. Comparison: the lowest fifth, or as the Canadian abstract reports it. Outcome: invasive breast cancer. Follow-up: a median of 11.7 years in the Cancer Prevention Study II cohort and an average of 14.6 years in the Women's Health Initiative; the Canadian abstract does not give follow-up.	Observational evidence starts at low. Risk of bias is serious, lowered 1 level: energy density came from one questionnaire at enrollment, which estimates food weight poorly. Inconsistency is serious, lowered 1 level: the Cancer Prevention Study II cohort reported a rate ratio of 1.20, from 1.05 to 1.36, while the Women's Health Initiative found a subhazard ratio of 1.06, from 0.97 to 1.1 as the paper rounds it, and the Canadian study did not detect a clear association. The 2 intervals overlap only between about 1.05 and 1.1, and the Canadian abstract gives no estimate, so its precision cannot be weighed. A result that is not statistically significant does not show that there is no association. Indirectness is not serious. Imprecision is not lowered separately: the first interval includes a 25 percent increase and the second excludes one, which is the disagreement counted under inconsistency. Publication bias cannot be judged from 3 studies. Low minus 2 reaches the floor of Very low. This row is provisional, because 2 of the 3 studies were read in abstract only.
Binge remission at the end of 6 months of treatment, adults with binge eating disorder and obesity, cognitive behavioral therapy plus low-energy-density counseling compared with therapy plus general nutrition counseling (research on energy density)	Very low, for no clear difference detected	GRADE, this page's own judgment, from one randomized trial (Masheb et al., 2011). Population: 50 adults with binge eating disorder and a body mass index of 30 or more. Intervention: therapy plus low-energy-density diet counseling; 25. Comparison: therapy plus general nutrition counseling not aimed at weight loss; 25. Outcome: no binge episodes in the 28 days before the end of treatment, from participants' own records and interviews. Follow-up: 6 months of treatment, with assessments to 12 months.	Randomized evidence starts at high. Risk of bias is serious, lowered 1 level: binge episodes were self-recorded by participants who knew which counseling they received, and 7 of 50 did not complete treatment. Inconsistency cannot be assessed from one trial. Indirectness is not serious for this comparison. Imprecision is very serious, lowered 2 levels: remission was 52 against 44 percent of all randomized participants, a difference of 8 percentage points with an interval this page approximates at minus 20 to 36, crossing both no difference and a 10-point threshold. Publication bias cannot be assessed. No upgrade. High minus 3 is Very low. This is not evidence that the counseling was harmful or helpful for binge eating.
Death from any cause in people following the named plan	Not rated	This page's own judgment. Population: adults. Intervention: the Volumetrics plan as published. Comparison: not following it. Outcome: death from any cause. Follow-up: any.	The searches did not identify a trial or cohort study of the named plan with this outcome, so there is no evidence body to rate. Not rated is an abstention, not a finding of no effect. The cohort research on energy density and death in the next row is not transferred to the plan.
Death from any cause over a median of 16.8 years, higher compared with lower energy density of the usual diet, middle-aged and older UK adults (cohort research on energy density)	Very low	GRADE, this page's own judgment, from one cohort analysis read in full with its supplement (Wang et al., 2026). Population: 208,312 UK Biobank participants, aged about 40 to 70 at enrollment, with at least one web-based 24-hour diet recall. Exposure: the UK Biobank energy density measure, averaged over 1 to 5 recalls, in kilojoules per gram, median 6.29, about 1.5 calories per gram; the paper does not say whether drinks were counted. Comparison: per 1 kilojoule per gram higher, about a quarter of a calorie per gram, and the highest against the lowest third. Outcome: death from any cause, from national registries; 12,617 deaths. Follow-up: a median of 16.8 years.	Observational evidence starts at low. Risk of bias is serious, lowered 1 level, for confounding: the main model adjusted for age, sex, ethnicity, education, deprivation, smoking, alcohol, physical activity and general health but not for body size, and when the authors also adjusted for overall diet quality, the association was no longer seen, a hazard ratio of 0.983, from 0.965 to 1.001. Energy density was also one of 63 nutrients tested in a hypothesis-free scan. Inconsistency cannot be assessed from one study; within it, the highest against the lowest third gave 1.05, from 0.999 to 1.11, and neither sex alone reached significance. Indirectness is not serious for this question about usual energy density. Imprecision is not serious for the main estimate: 1.017 per kilojoule per gram, from 1.004 to 1.030, which across the middle half of the cohort's range, about 2 kilojoules per gram, is roughly 1.04, from 1.01 to 1.06, if the relation is log-linear; that excludes no association and excludes a 25 percent relative increase, a common GRADE rule of thumb for an appreciable effect. Publication bias cannot be judged from one study. No upgrade. Low minus 1 is Very low. This is an observational association, not evidence that following the book, or changing energy density, changes survival.
Blood pressure, HbA1c and blood lipids, and separately cardiovascular events, the Volumetrics book added to a program compared with the same program without it	Not rated	This page's own judgment. Population: adults. Intervention: the Volumetrics book with lessons or classes added to a maintenance or workplace program. Comparison: the same program without the book. Outcomes: blood pressure, HbA1c and blood lipids as measured markers; heart attacks, strokes and other cardiovascular events as clinical events. Follow-up: any.	Markers: the 2 book trials measured them. In the primary care trial, total and LDL cholesterol rose less in the 2 groups given the energy density program, an effect no longer significant once weight change was accounted for, and blood pressure, triglycerides and HbA1c did not differ by group (Lowe et al., 2014); in the workplace trial, total cholesterol rose in the book group, largely through HDL (Lowe et al., 2010). These small package trials do not provide a sufficient body for the stated comparison. Events: no trial or cohort of the plan measured them, so cardiovascular events were not established. Not rated is an abstention, not a finding of no effect, and this page does not transfer ratings from energy density research or from cohort associations.
Onset or worsening of disordered eating in people following the named plan	Not rated	This page's own judgment. Population: people with and without a history of disordered eating. Intervention: the Volumetrics plan. Comparison: people not following it. Outcome: onset or worsening of disordered eating. Follow-up: any.	The searches did not identify a study with this design. The anorexia nervosa cohorts concern the energy density of diets after treatment, not the plan (Schebendach et al., 2008, 2012), and the 8-week online trial measured symptom change in people already diagnosed (Grammer et al., 2023); neither is transferred to this row.

How this archive talks about weight. This page reports what studies measured, including body weight, and does not treat weight change as a goal or as a measure of a diet's success. Weight a person loses without meaning to can be a sign of a health problem, and where it is, the page names it as a reason to see a clinician. People are described the way the study described them.

Last reviewed: Reviewed and approved by James Peth, MS, MPH, PhD, on October 21, 2026, after a combined final review of the fifth batch of 5 archive pages, the repairs it asked for and a targeted recheck. Written October 19, 2026. The class fee was rechecked and unchanged on October 21, 2026.

What changed after the combined final review: The banner rating is now Low rather than Very low, because a second deduction for imprecision in the first row rested on a different package. The cohort rows for weight, cancer and death are separated by the contrast or outcome each study measured, and each interval is compared with a stated threshold. A 2026 cohort analysis of energy density and death, a Canadian cancer study and a network review's published rating for a trial it labeled Volumetrics are added. The physician's role no longer names weight loss as a goal, and 2 passages that repeated or pointed to other pages' material are shortened.

What changed after the targeted recheck: The row for weight change by the energy density of the usual diet at the start is now Very low, provisional. Its reason no longer says the 2 cohorts disagree by more than their intervals allow, because the U.S. interval rested on group counts from the starting table rather than the numbers followed, and it now notes that the U.S. study adjusted for dietary fiber and caloric drinks as well as starting weight. The European comparison is now described as per 1 calorie per gram higher. No other rating changed.

The judgments in the table, apart from the one published rating, are this page's own, assigned from the evidence. Some sources could be read only as abstracts or author manuscripts, and the page says so where each is used. The Volumetrics books were not opened; the plan is described from published accounts of it. Prices are a snapshot from the pages opened on October 19, 2026, and can change.

Next scheduled review: Each year, because class prices and the U.S. News ratings change. Pages built on annual guidance are rechecked each year.

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Diet Reference Archive | One James

Prepared by James Peth, MS, MPH, PhD

© 2026–2027 One James. All rights reserved.

This page is for education and coaching practice. It is not medical or dietary advice.