Flexitarian Diet

Diet Reference Archive: a plant-forward eating pattern

Flexitarian Diet

A way of eating built mostly on plant foods that keeps meat, poultry or fish as an occasional part of the diet rather than cutting them out. Also called semi-vegetarian, it is promoted for weight control, heart health, diabetes prevention, a longer life and a smaller environmental footprint.

Family: Plant-based and plant-forward diets Promoted by: registered dietitian and author Dawn Jackson Blatner, sustainability researchers, and popular diet rankings First appeared: the word by 2003; the best-known popular book in 2009 GRADE: Very low for death from any cause, semi-vegetarian eating compared with eating meat more than once a week, in adults followed in long-term cohort studies, mainly Adventist Health Study-2 over a median of 11 years; 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. Back to the Diet Reference Archive index.

In brief

What is it? A mostly plant-based way of eating in which meat, poultry or fish are eaten now and then rather than every day. There is no single official version: one study may count anyone who eats meat less than once a week, another anyone who avoids red meat, and the popular book describes levels from 2 to 5 meatless days a week.

Does it work? The research is thin. In the largest long-term study, Adventist Health Study-2, people who ate meat between once a month and once a week did not have a clearly different death rate from people who ate meat more often, over a median of 11 years, and they were not clearly different for cancer. The same study linked semi-vegetarian eating with fewer new cases of type 2 diabetes over 2 years, a result that rests on few cases and self-report. In one 12-week trial, a diet that replaced most of the animal protein with plant protein lowered LDL cholesterol compared with a diet high in animal protein. In a 6-month weight trial, a semi-vegetarian group and an omnivorous group had similar average weight changes, but the trial was too small to show that the diets are equivalent. The certainty of these findings is low or very low.

Is it safe? For most healthy adults, eating less meat while keeping a varied diet raises no specific safety concern in the studies reviewed here. Two cautions matter most. In a 12-week trial in which the plant products were not fortified, replacing most of the animal protein with plant protein lowered vitamin B12 and iodine status, so what replaces the meat matters; certainty is moderate for the fall in B12 status. And in surveys of young women and university students, people who described themselves as semi-vegetarian, especially for weight reasons, reported more dietary restraint than omnivores and, in some samples, higher eating-disorder questionnaire scores. Those scores are not diagnoses, but they are a reason to listen for why a client is cutting back.

Who should not do it without talking to a doctor or dietitian first? Anyone who is pregnant or breastfeeding. Parents planning it for a child or teenager. Anyone with a history of disordered eating. Anyone whose eating changes raise a concern after the assessment described under Referral red flags. Anyone with kidney disease or another condition that has its own eating plan. Older adults with a small appetite or weight they are losing without meaning to. Anyone taking warfarin, insulin, a sulfonylurea or blood pressure medication who is planning a large change in what they eat.

Related pages: Mediterranean Diet, DASH Diet, and the Vegetarian Diet, Vegan Diet, Pescatarian Diet and Whole-Food Plant-Based Diet pages. The Vegan Diet page covers diets that exclude all animal foods. Full list on the archive index.

1. Overview

How the term is defined

"Flexitarian" joins "flexible" and "vegetarian." The American Dialect Society voted it the most useful new word of 2003 and defined it as "a vegetarian who occasionally eats meat" (American Dialect Society, 2004). A 2017 review of the health research used it for a diet that is primarily vegetarian with the occasional inclusion of meat or fish, treated "semi-vegetarian" as the same idea, and found that the studies defined it in many different ways (Derbyshire, 2017). A 2025 review of 86 studies found "flexitarian" used in 58 and "semi-vegetarian" in 47, with "meat reducer," "reducetarian," "demi-vegetarian" and others used less often, and concluded that the term has no formal definition, is mostly self-defined, and so can apply to diets with very different amounts of animal foods (Hess et al., 2025).

The definitions differ in ways that change who is counted. The Adventist Health Study-2, the main source of health data on this diet among the studies reviewed here, called people semi-vegetarian if they ate red meat or poultry at least once a month but less than once a week, or in some reports all meats including fish at least monthly but no more than weekly (Orlich et al., 2013; Tonstad et al., 2009). Other studies counted people who simply excluded red meat (Baines et al., 2007), people who ate meat no more than once a week (Mihrshahi et al., 2017), or, in the UK Biobank, "low meat-eaters" who ate red meat, processed meat or poultry up to 5 times a week (Watling et al., 2022).

This archive gives each related pattern its own page, and the line between them is drawn by what is eaten. A vegetarian diet excludes meat, poultry and fish; that is how the Academy of Nutrition and Dietetics defines it in its position paper (Raj et al., 2026), and it is covered on the Vegetarian Diet page. A pescatarian diet keeps fish but no meat or poultry and has its own page. A flexitarian diet keeps some meat, poultry or fish, eaten occasionally. One complication runs through the research: the Adventist Health Study-2 counted semi-vegetarians as one of its 4 "vegetarian" groups, so its combined "vegetarian" results include them (Abris et al., 2024; Orlich et al., 2013). This page reports only the semi-vegetarian group; the combined results belong to the Vegetarian Diet page.

What you eat

Most meals are built from vegetables, fruit, whole grains, beans, lentils, peas, nuts, seeds and soy foods. Eggs and dairy foods, or fortified plant milks, are usually part of the diet. Meat, poultry or fish appear in some meals, often in smaller portions, and are treated as one protein choice among several rather than the center of the plate.

Where a version gives numbers, they vary. The popular book, as summarized in a 2025 review, describes a beginner level of 2 meatless days a week, an advanced level of 3 or 4, and an expert level of 5 (Hess et al., 2025). The flexitarian pattern used in global modeling studies, adapted from the EAT-Lancet Commission, has at least 500 grams of fruit and vegetables and at least 100 grams of plant protein foods a day, whole grains, fewer than 2 servings a week each of poultry, fish and eggs, less than 1 serving of dairy a day, and 1 portion of red meat a week (Springmann et al., 2021).

What you avoid or limit

Nothing is strictly forbidden, which is the point of the name. What the versions limit is frequency: red and processed meat most of all, then poultry and fish, and in some versions eggs and dairy. The modeling version leaves out processed meat entirely (Springmann et al., 2018). Whether a limit is a rule or a goal is up to the person following it, which is why two people who both call themselves flexitarian can eat very differently.

Where it came from

The word was in public use by 2003, when the American Dialect Society named it the most useful new word of that year (American Dialect Society, 2004). Registered dietitian Dawn Jackson Blatner popularized it with her book The Flexitarian Diet, which U.S. News & World Report dates to 2009 and credits with coining the term (Chien, 2026). The Library of Congress record carries the publisher's description, which calls flexitarianism "the hot new term for healthy dieting that minimizes meat without excluding it altogether" (McGraw-Hill, n.d.).

The research label is older than the book. The Adventist Health Study-2, which enrolled about 97,000 adults in the United States and Canada between 2002 and 2007, grouped participants as vegans, lacto-ovo vegetarians, pesco-vegetarians, semi-vegetarians and nonvegetarians, and was publishing semi-vegetarian results by 2009 (Abris et al., 2024; Tonstad et al., 2009; Tonstad et al., 2013). More recently, sustainability research has adopted "flexitarian" for the low-meat reference diet used in global food system modeling (Springmann et al., 2018; Springmann et al., 2021).

Cultural and philosophical context

People give many reasons for eating less meat without giving it up. A review of the research lists health and weight, concern for animal welfare, the environment, the cost of meat, and sensory dislike of meat, and notes that many religious traditions limit meat on certain days or seasons (Forestell, 2018). People with strong ethical or religious reasons tend to adopt stricter vegetarian diets, while those who cut back for health or environmental reasons are more likely to reduce meat than to remove it (Forestell, 2018). The page rates only the health claims made for the diet, not any of these reasons.

What it claims to do

The publisher's description promises "Less meat = more weight loss and better health!" (McGraw-Hill, n.d.), and the subtitle of the book, as U.S. News gives it, is "The Mostly Vegetarian Way to Lose Weight, Be Healthier, Prevent Disease and Add Years to Your Life" (Chien, 2026). U.S. News states that a person can "reap all the health benefits of the vegetarian diet" without cutting out meat entirely (Chien, 2026). Its current page of top expert-recommended diets overall, as opened for this page, includes the flexitarian diet in an unnumbered list in which it appears third, after the Mediterranean and DASH diets (Burdeos, n.d.). Sustainability researchers claim a smaller environmental footprint (Springmann et al., 2018). Section 4 shows how far the evidence supports each claim.

What it gets right

The diet points people toward the foods that current heart-health guidance puts at the center: vegetables, fruit, whole grains, legumes and nuts. The American Heart Association's 2026 statement notes that dietary patterns higher in plant-based foods and lower in animal products have been associated with lower coronary heart disease risk, and that patterns higher in legumes and lower in red and processed meat have been associated with lower cardiovascular disease risk (Lichtenstein et al., 2026). The flexitarian approach also gives a person who is not willing to give up meat a way to move in that direction without an all-or-nothing rule, which is how young adults in one interview study described its appeal (Kemper & White, 2021).

How clients describe it, and what it gets confused with

Clients say "I'm flexitarian," "I'm mostly vegetarian," "I'm a part-time vegetarian," "I'm cutting back on meat," "I only eat meat on weekends," "I do Meatless Mondays," "I don't eat red meat," or "I eat plant-based but not strictly." Each can mean something different, from one meatless day a week to meat once a month. Ask what the client eats in a typical week before assuming.

It is easily confused with several neighbors, including the vegetarian and pescatarian diets described above. "Plant-based" can mean a fully plant diet or a plant-forward one, and the Whole-Food Plant-Based Diet page covers the version defined by food quality. The Mediterranean pattern also centers plant foods and keeps fish and some meat; its evidence is on the Mediterranean Diet page. The Planetary Health Diet, the EAT-Lancet pattern that modelers call flexitarian, is listed in the archive index under its own name.

2. In practice

A typical day of eating

Breakfast is oatmeal with walnuts and berries, or eggs with whole-grain toast and fruit. Lunch is lentil soup with bread and a salad, or a burrito bowl with black beans, rice, vegetables and salsa. A snack is yogurt, fruit, or hummus with carrots. Most dinners are built on beans, tofu, eggs or cheese, such as a vegetable stir-fry with tofu, chili made with beans, or pasta with chickpeas and greens. On 1 or 2 evenings a week, dinner includes a modest portion of chicken, fish or beef beside vegetables and a whole grain. The pattern is defined less by any single meal than by how often meat appears across the week.

Cost, products, and who profits

Whether the diet costs more depends on the country and on what replaces the meat. A global modeling study that priced diets in 150 countries found flexitarian diets 12 to 14 percent cheaper than current diets in upper-middle-income and high-income countries, but more expensive in lower-middle-income and low-income countries, where all the healthy and sustainable patterns it modeled cost 18 to 45 percent more than current diets (Springmann et al., 2021). A New Zealand study that modeled household shopping found the opposite at home: a flexitarian diet based on the EAT-Lancet pattern cost a family of 4 about NZ$728 a fortnight, against NZ$584 for the current diet, mainly because larger amounts of legumes, nuts, seeds and vegetables were needed to meet protein and other targets (Kidd et al., 2021). Both are models, not records of what people spent.

The cheaper route is built on dried or canned beans, lentils, eggs, frozen vegetables and whole grains. The more expensive route leans on packaged plant-based meat alternatives. The American Heart Association notes that these can help diversify protein choices but call for some caution, because "many are ultraprocessed and come with added sugars, sodium, stabilizers, and preservatives" (Lichtenstein et al., 2026). In a Dutch cohort, people with less education were consistently less likely to describe themselves as flexitarian, which suggests the label itself is unevenly spread (Zhu et al., 2025).

Several parties profit from the idea. The popular book and its author are one. Makers of meat alternatives are another; the 2017 review of flexitarian diets and health was funded by the company that makes Quorn products (Derbyshire, 2017). The meat industry has an interest too: the New Zealand trial that compared a flexitarian diet including red meat with a vegetarian diet including meat alternatives was partly funded by meat industry trade associations, which the authors state had no influence on the design, data collection or writing (Conner et al., 2025; Gillies et al., 2023). Knowing who paid for a study does not decide whether it is right, but it shapes the marketing a client has seen.

Environmental footprint

The environmental figures for this diet come from models, not from measurements in people. A global modeling study of more than 150 countries compared 4 balanced, mostly plant-based patterns, flexitarian, pescatarian, vegetarian and vegan, with current diets. Across the 4 patterns, modeled greenhouse gas emissions fell by 54 to 87 percent, nitrogen application by 23 to 25 percent, phosphorus application by 18 to 21 percent, cropland use by 8 to 11 percent and freshwater use by 2 to 11 percent; the paper's text reports these ranges rather than a separate figure for the flexitarian pattern. In low-income countries, the balanced patterns increased cropland use, freshwater use and phosphorus application, which the authors attribute partly to less efficient production and to current diets that are already high in staple crops (Springmann et al., 2018).

In the New Zealand household model, the flexitarian diet had about 263 kilograms of carbon dioxide equivalents a fortnight for a family of 4, against about 597 for the current diet and 203 for a vegan diet (Kidd et al., 2021). The same global study showed that what replaces meat matters: replacing animal foods with plant foods raised freshwater use by up to 16 percent (Springmann et al., 2018). For a person, the footprint of a flexitarian diet depends mostly on which meats are kept, how much, and what fills the rest of the plate.

Cultural fit

The diet fits easily with food traditions in which beans, lentils, grains and vegetables already carry most meals and meat is used in small amounts or saved for occasions. It asks more of households where meat is expected at most dinners, or where offering meat is part of hospitality. It can be adapted without losing what defines it by keeping a family dish and changing its proportions: more beans and vegetables in the stew, less meat, or a meatless version on some nights. Young adults in one interview study described compromising at social gatherings as the main reason they kept eating meat (Kemper & White, 2021).

What makes people stop

No study identified for this page measured why people stop a flexitarian diet. The closest evidence describes what keeps people eating meat. In 23 interviews with young adults in New Zealand, continued meat eating was driven mainly by social gatherings, and by associations of meat with variety, nutrients, fullness and taste, including cravings (Kemper & White, 2021). In a 10-week trial, participants who received red meat on top of a vegetarian base followed the plan more closely and were more satisfied with their allocation than those who received meat alternatives (Gillies et al., 2023). In a study of college women, all 57 who had been vegetarian or partly vegetarian and who answered a follow-up survey a year later said they still ate some form of that pattern (Forestell et al., 2012).

In a 6-month weight trial, adherence and acceptability did not differ clearly between a semi-vegetarian diet and vegan, vegetarian, pesco-vegetarian or omnivorous diets, according to the trial's abstract (Moore et al., 2015). Beyond these, the reasons a coach is likely to hear, such as cost, family meals, eating out and simply drifting back, are observation rather than measured data.

What happens when you stop

PREDITION reassessed participants 12 weeks after its 10-week intervention ended. It did not find clear differences between groups in changes in psychological outcomes at that follow-up, but participants were not randomized to stop, and ending the program did not establish that they stopped the diet (Conner et al., 2025). The searches did not identify a study that isolated health changes caused by stopping a flexitarian diet. Among the randomized general-adult trials included in this page, the longest intervention lasted 6 months (Turner-McGrievy, Davidson, et al., 2015). Longer, nonrandomized studies of disease-specific semi-vegetarian diets, including a 2-year Crohn disease report, were outside these comparisons (Chiba et al., 2010). In the 12-week Finnish trial, vitamin B12 and iodine status fell when most animal protein was replaced; whether they recover when a person eats more animal foods again was not studied (Pellinen et al., 2022).

Common variations

The popular book's 3 levels, from 2 to 5 meatless days a week, are the most familiar named version (Hess et al., 2025). "Semi-vegetarian" is used both for this diet and, in some studies, for people who avoid only red meat (Baines et al., 2007; Forestell et al., 2012). "Meatless Monday" and similar 1-day plans are often grouped with flexitarian eating but do not meet the definitions summarized in the 2025 review (Hess et al., 2025). "Reducetarian" and "meat reducer" describe cutting back without a fixed limit. The modeling version follows the EAT-Lancet pattern, which the archive index lists as the Planetary Health Diet (Springmann et al., 2021). Some studies split flexitarians further into pesco-, ovo-lacto- and vegan-leaning groups (Xu et al., 2026).

3. For the coach

SCOPE OF PRACTICE

A health and wellness coach does not prescribe, adjust, endorse, or discourage a flexitarian diet, 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. This diet needs a registered dietitian or physician when the person is pregnant or breastfeeding, is a child or teenager, has kidney disease or another condition with its own eating plan, takes medication affected by a large change in diet, has a history of disordered eating, or has questions about supplements such as vitamin B12, iodine or iron.

Who does what

The physician

Decides whether a large change in diet is safe for a person with a medical condition, and adjusts medication the change might affect, such as insulin, sulfonylureas, blood pressure medication or warfarin. Orders and reads blood tests when there is a question about vitamin B12, iron or iodine status, and works up symptoms or weight a person is losing without meaning to.

The registered dietitian

Plans the individual diet, including how often and which animal foods to keep, and which plant foods and fortified foods cover vitamin B12, iodine, iron, calcium and omega-3 fats. Adapts the plan to pregnancy, childhood, older age, sport or a diagnosed condition, and advises on supplements.

The health and wellness coach

Helps the client see their own reasons for eating less meat and what they hope will change. Explores how the plan fits their budget, cooking, family meals and social life; helps them build the habits that make it workable, such as planning meatless dinners or keeping beans on hand; notices how it is going; and listens for signs that cutting back has become a set of rigid rules. With the client's permission, can share general guidance from recognized authorities and explore what the client wants to do with it. Holds the referral line.

What a client bringing this diet needs

A client who says "I'm going flexitarian" is usually trying to eat more healthfully, spend less, or eat in a way that fits their values about animals or the environment, without the all-or-nothing rule of a vegetarian diet. Some want to lose weight, and for a few, cutting back on meat is one more rule in a growing list. What the coaching conversation offers that a search engine cannot is room to say what "flexitarian" means for this person, why it matters to them, and what a realistic week looks like, with the client deciding how far to go.

What to ask

• What does eating flexitarian look like for you in a usual week?
• What made you want to eat less meat, and what are you hoping will be different?
• How are meals with family or friends going since you started?

Referral red flags

A client whose list of avoided foods keeps growing beyond meat, who talks about cutting meat mainly to lose weight, who feels anxious or guilty about eating, or who is skipping meals with other people is worth asking about directly: what each restriction is for, whether it causes distress, whether it is narrowing what they eat, and whether it is getting in the way of daily life. Surveys have linked semi-vegetarian eating, especially for weight reasons, with more dietary restraint and higher eating-disorder questionnaire scores (Forestell, 2018; Sieke et al., 2022). There are ordinary reasons to eat less meat too. Where the answers raise a real concern, the coach follows their own referral process, or tells the client's clinician under an existing care plan.

A client who is pregnant or planning a pregnancy, is choosing this diet for a child, has kidney disease, or has questions about vitamin B12, iodine or iron supplements belongs with a registered dietitian or physician for those decisions. Weight a client loses without meaning to is a reason to involve a clinician, never a sign that the diet is working. A client taking insulin, a sulfonylurea, blood pressure medication or warfarin who plans a substantial change in eating keeps the prescriber informed before making it, which is the client keeping the prescriber in the loop rather than asking permission for every food choice.

Special populations

Pregnancy and breastfeeding

The searches for this page did not identify a trial of a flexitarian diet in pregnancy. In a United States pregnancy cohort of 1,948 women, 301 had a semi-vegetarian pattern by food questionnaire, eating meat, poultry and fish more than once a month but less than once a week. Their babies did not differ clearly in birthweight, but they had higher odds of being small for gestational age, an odds ratio of 1.98 (95 percent confidence interval 1.24 to 3.17), with no clear increase in small size combined with illness after birth (Yisahak et al., 2021). This is an association in one cohort and does not show that the diet caused smaller babies. Federal guidance names people who follow vegetarian diets, and the infants of women who follow vegan diets, among the groups at risk of vitamin B12 deficiency (NIH Office of Dietary Supplements, 2025b). Diet in pregnancy and breastfeeding belongs with the obstetric clinician and a registered dietitian.

Children and adolescents

The searches did not identify a trial of a flexitarian diet in children or adolescents. In a cross-sectional study of 165 Norwegian 16 to 24 year olds, including flexitarians, the risk of inadequate intake of most micronutrients was low, partly because many took supplements, but inadequate intakes of iodine, vitamin D and selenium were common in some of the diet groups (Groufh-Jacobsen et al., 2024). A survey of university students linked semi-vegetarian eating with higher eating-disorder questionnaire scores (Sieke et al., 2022). A child's diet belongs with the family, the pediatrician and a registered dietitian.

Older adults

In a 4-week trial in Australians aged 65 to 75, all food was provided and a semi-vegetarian diet with 70 percent of protein from plants lowered diastolic blood pressure more than an omnivorous diet with 50 percent, while all 4 study diets improved several health measures compared with participants' usual eating (Ribeiro et al., 2024). In a cross-sectional survey of 11,437 Chinese adults aged 65 and older, eating meat no more than 3 times a month was linked with higher odds of depression and cognitive impairment (Xu et al., 2026); a survey of this kind cannot tell whether eating less meat came before or after poorer health. Older adults are at higher risk of vitamin B12 deficiency (NIH Office of Dietary Supplements, 2025b). A small appetite or unintended weight loss is a reason to involve a clinician.

Athletes and people with high activity

The searches did not identify a trial of a flexitarian diet in athletes. A cross-sectional survey of recreational endurance runners described the eating habits and race-day strategies of 34 flexitarian runners alongside vegetarian and vegan runners, without measuring performance (Tanous et al., 2024). Questions about protein, iron or energy needs for training belong with a registered dietitian.

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

The searches did not identify a medication interaction specific to this diet. Any client taking insulin, a sulfonylurea, blood pressure medication or warfarin who plans a substantial change in eating keeps the prescriber informed before making it. A possible low blood sugar episode calls for immediate action under the client's own plan; severe symptoms, or an episode the person cannot manage, call for emergency help; and the client tells the prescriber about the episode afterward.

People with a history of disordered eating

The diet's flexibility can make it gentler than a strict vegetarian diet, but the studies of eating behavior point the other way for some people. In surveys of young women and students, people who called themselves semi-vegetarian or flexitarian reported more dietary restraint than omnivores, and in some samples higher eating-disorder questionnaire scores, especially when weight was the reason (Forestell et al., 2012; Sieke et al., 2022; Timko et al., 2012). Distress, narrowing and interference with daily life are what raise a concern, and a concern goes through the coach's own referral process or to the client's clinician under an existing care plan.

Client misconceptions

Three come up most. The first is that flexitarian eating gives all the benefits of a vegetarian diet without giving up meat. In the largest cohort, semi-vegetarians' death rate was not clearly different from that of people who ate meat more often (Abris et al., 2024). The second is that it is a weight-loss diet; in the one 6-month trial identified, semi-vegetarian and omnivorous advice produced similar average weight changes, in a trial too small to show the diets are equivalent (Turner-McGrievy, Davidson, et al., 2015). The third is that any meatless meal is a healthy one. What replaces the meat decides that, and the American Heart Association cautions that many meat alternatives are ultraprocessed (Lichtenstein et al., 2026). Each is taken up in section 6.

🤝 COACHING CONNECTION

Daniel tells the coach he wants to cut meat down to 2 dinners a week, to save money and because he worries about the environment, but a video he watched said he would run short of vitamin B12. The coach asks what a usual week of meals looks like now and what he has in mind for the meatless nights. Daniel describes a few dishes he already likes and says he is not sure about the vitamin question. The coach asks whether he would like to hear what a federal health agency says, and he says yes.

The coach shares that the agency lists foods of animal origin and some fortified foods as sources of B12, and adds that whether a person needs a supplement is a question for a doctor or dietitian. Daniel decides to plan 3 meatless dinners for the next 2 weeks and to ask about B12 at his next checkup. The coach did not recommend the diet or a supplement.

4. The evidence

(select the heading to open or close this section)

Very little research tests a flexitarian diet by name. Most of the evidence comes from 2 kinds of study: large cohort studies that compared people who ate meat only occasionally with people who ate it more often, mainly in the Adventist Health Study-2, and short trials that replaced part of the animal protein in a diet with plant protein. The cohorts found no clear difference in death rates or cancer for semi-vegetarians, and fewer new cases of diabetes in one short follow-up; the trials found changes in blood lipids and nutrient status over weeks to months. No trial identified for this page measured heart attacks, strokes, cancer or death. The ratings below are low or very low in certainty, apart from a moderate rating for a fall in vitamin B12 status when unfortified plant foods replace animal protein.

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. The searches for this page identified 5 trials that included a flexitarian or semi-vegetarian arm, or a diet that kept some meat while replacing much of the animal protein with plant protein. They lasted 4 weeks to 6 months and enrolled 19 to 145 people each. A 2026 systematic review of trials that partly replaced animal protein foods with plant protein foods in healthy adults found 4 such interventions reported in 7 articles; this page read only its abstract (Courtney et al., 2026).

Cardiometabolic outcomes

In the ScenoProt trial in Finland, 145 healthy adults aged 20 to 69 were randomized to 1 of 3 diets for 12 weeks, and 136 finished. The diets differed in where protein came from: 70 percent from animal foods, which was close to the usual Finnish diet; 50 percent; or 30 percent, with much of the meat and dairy replaced by plant protein foods such as legume and vegetable dishes, nuts, seeds, cereals and plant-based dairy alternatives, and fish held at 2 meals a week in every group.

Total and LDL cholesterol were lower after the 30 percent animal protein diet than after the 70 percent diet, with no clear difference in HDL cholesterol or triglycerides. Saturated fat intake was lower and fiber intake higher on the 2 more plant-based diets. The paper reports the lipid comparison as a statistical test and a figure; read from that figure, after adjustment for starting values, total cholesterol was about 0.35 mmol/L lower and LDL cholesterol about 0.3 mmol/L lower on the 30 percent diet than on the 70 percent diet (Päivärinta et al., 2020).

In the Nutrition for Healthy Living trial in Australia, 128 adults aged 65 to 75 were randomized to 1 of 4 diets for 4 weeks, with all food provided, and 113 finished; the methods section gives 129 randomized. The diets crossed 2 protein sources, a semi-vegetarian diet with 70 percent of protein from plants and an omnivorous diet with 50 percent, with 2 fat-to-carbohydrate ratios. Diastolic blood pressure fell more on the semi-vegetarian diets. Total cholesterol and glucose also differed by protein source at first, but not after adjustment for age, sex, body mass index and physical activity (Ribeiro et al., 2024).

In a 4-week crossover trial in 19 men at raised cardiometabolic risk, a diet with 64 percent of protein from plants was compared with one with 36 percent; risk factors improved over time on both, and the trial's abstract reports no clear difference between diets in blood vessel function and only a trend for insulin resistance (Lépine et al., 2024).

The New Zealand PREDITION trial compared 2 flexitarian-related diets with each other rather than with a usual diet: about 3 servings a week of red meat, or of plant-based meat alternatives, on top of a vegetarian base, for 10 weeks. Its cardiometabolic report, read only as an abstract, found no clear difference between groups in cardiometabolic markers (Morton et al., 2026). The review of partial-replacement trials reports, in its abstract, improvements in LDL cholesterol, total cholesterol and body weight in the groups eating more plant protein (Courtney et al., 2026); this page did not see its tables and does not use its findings for a rating.

Cancer

The searches for this page did not identify a trial of a flexitarian or semi-vegetarian diet that measured cancer. The trials identified lasted at most 6 months, which is too short to observe cancer outcomes.

Body weight, as measured

The New DIETs trial in South Carolina randomized 63 adults with overweight or obesity to 1 of 5 low-fat, low-glycemic-index diets for 6 months: vegan, vegetarian, pesco-vegetarian, semi-vegetarian (13 people) or omnivorous, and 50 finished. Weight change at 6 months was -3.2 percent (standard deviation 3.8) in the semi-vegetarian group and -3.1 percent (3.6) in the omnivorous group, and the vegan group's -7.5 percent was greater than both. This page's approximate 95 percent interval for the semi-vegetarian against omnivorous difference, which the trial did not report, is -3.2 to +3.0 percentage points, so the result does not show the diets are equivalent. The groups were not run identically: the omnivorous control group met monthly with weekly emails, while the others met weekly for the first 2 months (Turner-McGrievy, Davidson, et al., 2015).

In the Finnish trial, body mass index did not differ between the 3 diets at 12 weeks (Päivärinta et al., 2020). Weight is reported here as a measurement, not as a goal.

Mortality

The searches for this page did not identify a trial of a flexitarian or semi-vegetarian diet that measured death. Evidence on death comes only from the cohort studies below.

Eating behavior and wellbeing

In PREDITION, 80 healthy young adults in Auckland took part, assigned to a red meat or a meat-alternative arm. Participants entered as 40 household pairs organized into 8 sets of 5 pairs; the methods say the sets were randomized, although the abstract describes assignment by pair (Conner et al., 2025; Gillies et al., 2023). Of the 80, 78 finished; 1 pair in the meat-alternative arm withdrew because of digestive discomfort (Gillies et al., 2023). Weekly measures of well-being, depression, anxiety, stress and fatigue did not differ clearly between the arms over 10 weeks (Conner et al., 2025). Adherence scores were higher in the red meat group, 96.1 against 86.7 out of 100, and that group was generally more satisfied with its allocation; both groups ate more vegetables and reported more positive eating experiences than at baseline (Gillies et al., 2023).

In New DIETs, according to the abstract of a separate report, the vegan, vegetarian and pesco-vegetarian groups improved their Dietary Inflammatory Index scores more than the semi-vegetarian group at 2 months, with no clear difference at 6 months (Turner-McGrievy, Wirth, et al., 2015).

Nutrient intake and status

In the Finnish trial, vitamin B12 intake and status, measured as holotranscobalamin in blood, were lower at 12 weeks on the 30 percent animal protein diet than on the 50 or 70 percent diets, and B12 intake was also lower on the 50 percent diet than on the 70 percent diet. Iodine intake and status were lower on both of the more plant-based diets. Iron and folate intakes were higher on the most plant-based diet, with no clear difference in the blood markers of either (Pellinen et al., 2022). In PREDITION, serum vitamin B12 rose by 13 ng/L in the red meat group and fell by 31 ng/L in the meat-alternative group, a difference of 46 ng/L (95 percent confidence interval 7 to 84), with both groups well above deficiency thresholds (Conner et al., 2025).

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. For this diet, almost all the cohort evidence comes from the Adventist Health Study-2, which enrolled about 97,000 adults in the United States and Canada between 2002 and 2007, classified their diets once from a food questionnaire, and has followed them through national death and cancer registries (Abris et al., 2024; Tonstad et al., 2013). About 5 to 6 percent of participants were semi-vegetarian, and the reference group of nonvegetarians ate relatively little meat by general population standards (Orlich et al., 2013; Tantamango-Bartley et al., 2013). Other cohorts, in Australia, Sweden and the United Kingdom, used different definitions.

Cardiometabolic outcomes

In a 2-year follow-up of 41,387 Adventist Health Study-2 participants without diabetes, new diabetes was reported by 0.92 percent of the 2,404 semi-vegetarians and 2.12 percent of nonvegetarians. After adjustment for age, body mass index and other factors, the odds ratio for semi-vegetarians was 0.49 (95 percent confidence interval 0.31 to 0.76); among Black participants the estimate was similar but uncertain, 0.47 (0.15 to 1.44). Diabetes was self-reported, without blood testing (Tonstad et al., 2013). In the cross-sectional baseline data, 6.1 percent of semi-vegetarians had type 2 diabetes against 7.6 percent of nonvegetarians, an adjusted odds ratio of 0.76 (0.65 to 0.90) (Tonstad et al., 2009). A 2017 review of flexitarian diets reports the semi-vegetarian prevalence as 4.8 percent in one sentence, which is the paper's figure for pesco-vegetarians; its own table gives the correct 6.1 percent (Derbyshire, 2017).

For heart disease, the Adventist Health Study-2 semi-vegetarian results are imprecise. In the first mortality analysis, the hazard ratio for death from cardiovascular disease was 0.85 (95 percent confidence interval 0.63 to 1.16) and for ischemic heart disease 0.92 (0.57 to 1.51) (Orlich et al., 2013); the longer follow-up left semi-vegetarians out of its cause-specific figure, citing space and the lack of results whose intervals excluded no difference (Abris et al., 2024). A metabolic-syndrome substudy combined semi-vegetarians with fish-only eaters, so it does not isolate the group rated on this page (Rizzo et al., 2011).

Cancer

In the Adventist Health Study-2, semi-vegetarians did not have a clearly different rate of cancer overall: 182 cancers among 3,881 semi-vegetarians over about 4 years, a hazard ratio of 0.98 (95 percent confidence interval 0.83 to 1.18) compared with nonvegetarians (Tantamango-Bartley et al., 2013). The same was true, with wide intervals, for colorectal cancer, 0.92 (0.62 to 1.37), based on 30 cases (Orlich et al., 2015); breast cancer, 0.91 (0.67 to 1.23), based on 49 cases (Penniecook-Sawyers et al., 2016); and prostate cancer, 1.18 (0.91 to 1.54), based on 63 cases (Tantamango-Bartley et al., 2016). Among premenopausal women, semi-vegetarians had a higher rate of breast cancer, 1.96 (1.12 to 3.43), based on 15 cases, a result from one of many subgroup comparisons in that paper (Penniecook-Sawyers et al., 2016).

UK Biobank's "low meat-eater" category allowed meat up to 5 times a week, so its cancer results are not treated here as evidence about semi-vegetarian diets (Watling et al., 2022). Godos and colleagues' review grouped several unlike exposures as semi-vegetarian, including a fruit-and-vegetable dietary cluster. Because that pool does not isolate the semi-vegetarian pattern defined here, its pooled cancer association is not used on this page (Godos et al., 2017).

Body weight, as measured

In Adventist Health Study-2 baseline data, mean body mass index was 27.3 in semi-vegetarians and 28.8 in nonvegetarians (Tonstad et al., 2009). In the Swedish Mammography Cohort, according to its abstract, 960 women who called themselves semi-vegetarian had lower odds of overweight or obesity than omnivores, an odds ratio of 0.52 (0.43 to 0.62) (Newby et al., 2005). Among 9,113 young Australian women, semi-vegetarians, defined there as women who excluded red meat, had a mean body mass index of 23.0 against 23.7 in non-vegetarians (Baines et al., 2007). Among older Australian women, the 45 semi-vegetarians did not differ clearly from regular meat eaters (Ferguson et al., 2022). All of these compare people at one point in time and cannot show that the diet changed anyone's weight.

Mortality

In the first Adventist Health Study-2 mortality analysis, 73,308 adults were followed for a mean of 5.8 years; among 4,031 semi-vegetarians there were 160 deaths, and the hazard ratio for death from any cause was 0.92 (95 percent confidence interval 0.75 to 1.13) compared with nonvegetarians (Orlich et al., 2013). The longer follow-up, of 88,400 adults for a median of 11.1 years with 12,515 deaths, found a fully adjusted hazard ratio of 0.99 (0.92 to 1.07) for semi-vegetarians, based on 764 deaths (Abris et al., 2024).

In the Australian 45 and Up Study, 243,096 adults were followed for a mean of 6.1 years, and people who ate meat once a week or less had a fully adjusted hazard ratio of 1.12 (0.96 to 1.31) compared with regular meat eaters (Mihrshahi et al., 2017). None of these analyses, from 2 independent cohorts, found a clear difference.

Evidence from cross-sectional studies

Several surveys compared people who already eat this way with other groups at a single point in time, which cannot show which came first. In repeated surveys of 10,797 adults in Geneva, flexitarians, defined by questionnaire as eating red meat or poultry at least monthly but no more than weekly, were 15.6 percent of the population, and the groups that ate less meat had lower body mass index, total cholesterol and blood pressure than omnivores (Wozniak et al., 2020).

In a Dutch cohort in which people named their own diet, the share calling themselves flexitarian rose from 3.50 percent to 7.16 percent over about 15 years (Zhu et al., 2025), and in a weighted online survey of 3,000 Americans in 2024, 5 percent said they had followed a flexitarian eating pattern in the past year (International Food Information Council, 2024). The gap between these figures shows how much the definition, and whether people name the diet themselves, changes the count.

Studies of eating behavior point to a group that needs attention. In Timko and colleagues' first study, semi-vegetarians scored higher on some eating-behavior measures, although the overall Eating Attitudes Test difference was not statistically clear. Their second study found little evidence of greater eating-related pathology once questionnaire items about avoiding foods were considered. These scores are not diagnoses, and the studies cannot show that the diet caused an eating disorder (Timko et al., 2012). College women who were semi-vegetarian or flexitarian reported more dietary restraint than omnivores, with weight control as a leading motive (Forestell et al., 2012). Among 1,585 university students, semi-vegetarians had the highest eating disorder scores, especially those who chose the diet for weight or health, according to the abstract (Sieke et al., 2022).

Research on broad plant-rich dietary patterns, scored by indexes, is discussed on the Whole-Food Plant-Based Diet page; it does not isolate people eating a semi-vegetarian diet.

Highlighted studies

These 4 studies carry the most weight for this page: the longest cohort follow-up, the cohort analysis behind the diabetes finding, a 12-week trial of replacing animal protein, and the one trial that set a flexitarian diet directly against a vegetarian one.

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

Highlighted studies for the Flexitarian Diet

Study	Design	Sample size	Duration	Finding	The limitation that matters
Abris et al., 2024, Adventist Health Study-2	Prospective cohort	88,400 adults; 764 deaths among semi-vegetarians	Median 11.1 years	Death from any cause: hazard ratio 0.99 (0.92 to 1.07) for semi-vegetarians against nonvegetarians	Diet measured once at baseline, in a health-conscious church-based population
Tonstad et al., 2013, Adventist Health Study-2	Prospective cohort	41,387 adults without diabetes; 2,404 semi-vegetarians	2 years	New diabetes in 0.92 percent of semi-vegetarians against 2.12 percent of nonvegetarians; adjusted odds ratio 0.49 (0.31 to 0.76)	Self-reported diabetes, short follow-up and few cases among semi-vegetarians
Päivärinta et al., 2020, and Pellinen et al., 2022, ScenoProt	Randomized controlled trial of 3 diets with 70, 50 or 30 percent of protein from animal foods	145 randomized, 136 finished	12 weeks	Lower total and LDL cholesterol on the 30 percent diet than on the 70 percent diet; lower vitamin B12 and iodine status on the more plant-based diets	Healthy, well-educated volunteers on a prescribed diet; effect sizes for lipids shown only in a figure
Gillies et al., 2023, and Conner et al., 2025, PREDITION	Randomized trial of 8 sets of household pairs: red meat against meat alternatives on a vegetarian base	80 young adults in 40 household pairs; 78 finished	10 weeks	No clear difference in well-being or mood; higher adherence and serum vitamin B12 in the red meat group	Small, unblinded, partly funded by the meat industry, and compared 2 low-meat diets rather than a usual diet

Head to head

Three trials set a semi-vegetarian or flexitarian diet against named alternatives. In New DIETs, the semi-vegetarian group lost less weight at 6 months than the vegan group, and its average weight change was similar to those of the omnivorous and pesco-vegetarian groups, which does not show that those diets are equivalent (Turner-McGrievy, Davidson, et al., 2015). In PREDITION, a flexitarian diet with red meat and a vegetarian diet with meat alternatives did not differ clearly in mood, well-being or cardiometabolic markers, while vitamin B12 status and adherence favored the flexitarian arm (Conner et al., 2025; Gillies et al., 2023; Morton et al., 2026).

In ScenoProt, a diet with 30 percent of protein from animal foods lowered LDL cholesterol compared with one at 70 percent, while the 50 percent diet sat in between on several measures (Päivärinta et al., 2020; Pellinen et al., 2022).

Where the evidence is absent

The searches for this page did not identify a trial of a flexitarian diet that measured heart attacks, strokes, cancer or death. Among the randomized general-adult trials included here, the longest lasted 6 months; longer, nonrandomized studies of disease-specific semi-vegetarian diets were outside these comparisons. The searches did not identify a trial in pregnancy, children, adolescents or athletes, or a study that isolated health changes caused by stopping the diet. The cohort evidence comes mostly from one population, the Adventist Health Study-2, and each study defined the diet differently, so the results may not apply to people who call themselves flexitarian elsewhere. A trial registry search found a registered trial of a flexitarian diet combined with time-restricted eating, with no results posted. Findings from reports read only as abstracts are marked as such where they are used.

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

The clearest effects of eating less meat are on what goes into the diet. In the Finnish trial, replacing animal protein foods with plant protein foods lowered saturated fat intake and raised polyunsaturated fat and fiber intake, and the authors give the change in dietary fat as the likely explanation for the fall in LDL cholesterol, with lower cholesterol intake possibly playing a part (Päivärinta et al., 2020). Vitamin B12 occurs naturally in animal foods and is added to fortified foods, which is why B12 status fell when animal foods were cut back and the replacements were not fortified (NIH Office of Dietary Supplements, 2025b; Pellinen et al., 2022). Meat, poultry and seafood supply heme iron, which is absorbed better than the nonheme iron in plant foods, and federal guidance notes that people who follow vegetarian diets need more iron for that reason (NIH Office of Dietary Supplements, 2025a).

Proposed mechanisms

In a 4-week crossover trial in 19 men, a flexitarian diet high in plant protein changed some gut bacteria and shifted how the gut handled tryptophan, an amino acid, toward products that the authors link with cardiometabolic health, possibly because of the extra fiber from legumes (Lépine et al., 2026). The same trial reported changes in blood metabolites that the authors describe as possibly beneficial (Lépine et al., 2024). These are proposed pathways from a small, short study and do not support any claim in section 4.

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 professional or regulatory warning against the flexitarian diet itself. The American Heart Association cautions about one common ingredient of it: plant-based meat alternatives can help diversify protein choices, but "many are ultraprocessed and come with added sugars, sodium, stabilizers, and preservatives" (Lichtenstein et al., 2026).

Nutrient gaps

Keeping some animal foods provides additional potential sources of vitamin B12, iron and other nutrients. Adequacy still depends on the amounts eaten, the foods that replace meat, and whether fortified foods or supplements are used. Vitamin B12 occurs naturally in animal foods and is added to fortified foods, and federal guidance lists people who follow vegetarian diets and older adults among the groups at risk of deficiency (NIH Office of Dietary Supplements, 2025b). In the Finnish trial, B12 and iodine status fell within 12 weeks when 70 percent of protein came from plants, while iron status did not change clearly (Pellinen et al., 2022). None of the plant-based products supplied in that trial were fortified with vitamin B12 or iodine, so results may differ where fortified foods are used (Pellinen et al., 2022).

As meat is reduced, attention to iron sources and bioavailability becomes more important; the amount needed depends on the person's diet and life stage (NIH Office of Dietary Supplements, 2025a). A systematic review of observational studies found that semi-vegetarian diets had the lowest share of protein from plants of 4 plant-based diets, from 37 to 83 percent, with total protein in the semi-vegetarian studies at 13.7 to 16.5 percent of energy; these are group averages and do not show that every person's intake was adequate (Rolands et al., 2025). In PREDITION, a long-chain omega-3 fat in the blood fell for a time in the meat-alternative group and not in the red meat group, according to the abstract (Morton et al., 2026). The Vegan Diet page covers these nutrients in more depth. Numbers for an individual, and any supplement, belong with a registered dietitian or physician.

Who should not follow it without medical supervision

No group identified in the searches for this page needs to avoid eating less meat altogether. The groups who should plan the diet with a clinician or registered dietitian are people who are pregnant or breastfeeding, because of the small-for-gestational-age association in one cohort and the B12 guidance (NIH Office of Dietary Supplements, 2025b; Yisahak et al., 2021); children and adolescents; older adults with a small appetite or unintended weight loss; people with kidney disease, whose needs depend on stage, laboratory results and dialysis and whose plan belongs with the kidney care team; and people with a history of disordered eating, because of the restraint findings in section 4 (Sieke et al., 2022; Timko et al., 2012).

Medication interactions

The searches for this page did not identify a medication interaction specific to the flexitarian diet. The general rule applies: a client taking insulin, a sulfonylurea, blood pressure medication or warfarin who plans a substantial change in eating keeps the prescriber informed before making it. A coach never adjusts medication; the point of naming them is to know when to send the client back to the prescriber.

Signs it is going wrong

A coach or family member might notice tiredness, weight loss the person did not intend, or a list of avoided foods that keeps growing beyond meat. Behavioral signs include anxiety or guilt about eating meat or any other food, rigid rules about meals, secrecy, or pulling away from meals with others. Persistent physical symptoms or unintended weight loss call for clinical follow-up. For food rules or changes in social eating, the coach first explores purpose, distress, narrowing and interference with daily life; a real concern follows their own referral process or the client's existing care plan.

Myths and where they came from

Myth: "Blatner invented the word in 2009."

U.S. News credits the registered dietitian Dawn Jackson Blatner with coining the term in her 2009 book (Chien, 2026). The American Dialect Society had already voted "flexitarian" the most useful new word of 2003 (American Dialect Society, 2004). Blatner popularized it; she did not originate it.

Myth: "You get all the benefits of being vegetarian without giving up meat."

The claim appears on the U.S. News page for the diet (Chien, 2026). In the Adventist Health Study-2, semi-vegetarians' death rate over 11 years was not clearly different from that of people who ate meat more often (Abris et al., 2024). The vegetarian groups' own results are on the Vegetarian Diet page. The evidence does not show that eating meat occasionally gives the same benefits as a vegetarian diet.

Myth: "It is a weight-loss diet."

The publisher's description promises "more weight loss" (McGraw-Hill, n.d.). In the one 6-month trial identified, average weight change on semi-vegetarian advice was similar to that on omnivorous advice, in a trial too small to show the diets are equivalent (Turner-McGrievy, Davidson, et al., 2015). The lower body mass index of semi-vegetarians in surveys comes from comparisons at one point in time, not from following people who changed their diet.

Myth: "Any meatless meal is healthier."

What replaces the meat decides that. The American Heart Association cautions that many plant-based meat alternatives are ultraprocessed (Lichtenstein et al., 2026), and the benefits seen in the Finnish trial came with more legumes, nuts, seeds and fiber (Päivärinta et al., 2020).

7. Key terms

Flexitarian

A person or diet that is mostly vegetarian but includes meat, poultry or fish occasionally; the word joins "flexible" and "vegetarian."

Semi-vegetarian

A research term often used for the same diet, defined differently across studies, for example eating meat at least monthly but less than weekly, or avoiding only red meat.

Meat reducer

A person who eats less meat than before without setting a fixed limit; also called a reducetarian.

Plant-based meat alternative

A manufactured product designed to replace meat in a meal, such as a plant-based burger or sausage.

Adventist Health Study-2

A cohort of about 97,000 adults in the United States and Canada, enrolled from 2002 to 2007, that classified people by how often they ate meat and other animal foods.

Hazard ratio

A comparison of how often an event happens over time in one group against another; 1.0 means no difference, and below 1.0 means a lower rate.

Odds ratio

A comparison of the odds of an outcome in one group against another, often used in surveys and short follow-ups; 1.0 means no difference.

Small for gestational age

A baby who is small for the length of the pregnancy, judged against a standard growth reference.

Holotranscobalamin

A form of vitamin B12 in the blood, measured in research as a marker of B12 status.

Dietary restraint

Deliberately holding back on eating, usually to control weight, measured in research by questionnaire.

8. Review questions

1. How do the definitions of "flexitarian" used by the American Dialect Society, the popular book's levels and the Adventist Health Study-2 differ, and why does that matter when a client says "I'm flexitarian"?
2. In the Adventist Health Study-2, what was compared, in whom and for how long, and what did the semi-vegetarian group show for death from any cause and for new cases of diabetes? Draw on section 4.
3. A client says she has gone flexitarian to lose weight, has also stopped eating bread and dessert, and now skips family dinners. What does the coach ask, and where is the referral line?
4. Where does the claim that flexitarians get "all the health benefits of the vegetarian diet" come from, and what does the evidence in section 4 show?

9. References

Abris, G. P., Shavlik, D. J., Mathew, R. O., Butler, F. M., Oh, J., Sirirat, R., Sveen, L. E., & Fraser, G. E. (2024). Cause-specific and all-cause mortalities in vegetarian compared with those in nonvegetarian participants from the Adventist Health Study-2 cohort. American Journal of Clinical Nutrition, 120(4), 907-917. https://doi.org/10.1016/j.ajcnut.2024.07.028

American Dialect Society. (2004, January 13). 2003 words of the year. americandialect.org/2003_words_of_the_year

Baines, S., Powers, J., & Brown, W. J. (2007). How does the health and well-being of young Australian vegetarian and semi-vegetarian women compare with non-vegetarians? Public Health Nutrition, 10(5), 436-442. https://doi.org/10.1017/S1368980007217938

Burdeos, J. (n.d.). Top expert-recommended diets overall. U.S. News & World Report. Retrieved October 4, 2026, from health.usnews.com/best-diet/best-diets-overall

Chiba, M., Abe, T., Tsuda, H., Sugawara, T., Tsuda, S., Tozawa, H., Fujiwara, K., & Imai, H. (2010). Lifestyle-related disease in Crohn's disease: Relapse prevention by a semi-vegetarian diet. World Journal of Gastroenterology, 16(20), 2484-2495. https://doi.org/10.3748/wjg.v16.i20.2484

Chien, S. (2026, January 8). Flexitarian diet. U.S. News & World Report. health.usnews.com/best-diet/flexitarian-diet

Conner, T. S., Gillies, N. A., Worthington, A., Bermingham, E. N., Haszard, J. J., Knowles, S. O., Bernstein, D. R., Cameron-Smith, D., & Braakhuis, A. J. (2025). Effect of moderate red meat intake compared with plant-based meat alternative on psychological well-being: A 10-wk cluster randomized intervention in healthy young adults. Current Developments in Nutrition, 9(1), Article 104507. https://doi.org/10.1016/j.cdnut.2024.104507

Courtney, A., Sweeney, R., McNulty, B., Wallace, M., & Brennan, L. (2026). Partially replacing animal-based protein foods with plant-based protein foods: A systematic review of randomized controlled trials in healthy adults. Nutrition Reviews. Advance online publication. https://doi.org/10.1093/nutrit/nuag058

Derbyshire, E. J. (2017). Flexitarian diets and health: A review of the evidence-based literature. Frontiers in Nutrition, 3, Article 55. https://doi.org/10.3389/fnut.2016.00055

Ferguson, J. J., Oldmeadow, C., Mishra, G. D., & Garg, M. L. (2022). Plant-based dietary patterns are associated with lower body weight, BMI and waist circumference in older Australian women. Public Health Nutrition, 25(1), 18-31. https://doi.org/10.1017/S1368980021003852

Forestell, C. A. (2018). Flexitarian diet and weight control: Healthy or risky eating behavior? Frontiers in Nutrition, 5, Article 59. https://doi.org/10.3389/fnut.2018.00059

Forestell, C. A., Spaeth, A. M., & Kane, S. A. (2012). To eat or not to eat red meat. A closer look at the relationship between restrained eating and vegetarianism in college females. Appetite, 58(1), 319-325. https://doi.org/10.1016/j.appet.2011.10.015

Gillies, N. A., Worthington, A., Li, L., Conner, T. S., Bermingham, E. N., Knowles, S. O., Cameron-Smith, D., Hannaford, R., & Braakhuis, A. (2023). Adherence and eating experiences differ between participants following a flexitarian diet including red meat or a vegetarian diet including plant-based meat alternatives: Findings from a 10-week randomised dietary intervention trial. Frontiers in Nutrition, 10, Article 1174726. https://doi.org/10.3389/fnut.2023.1174726

Godos, J., Bella, F., Sciacca, S., Galvano, F., & Grosso, G. (2017). Vegetarianism and breast, colorectal and prostate cancer risk: An overview and meta-analysis of cohort studies. Journal of Human Nutrition and Dietetics, 30(3), 349-359. https://doi.org/10.1111/jhn.12426

Groufh-Jacobsen, S., Larsson, C., Margerison, C., Mulkerrins, I., Aune, D., & Medin, A. C. (2024). Micronutrient intake and status in young vegans, lacto-ovo-vegetarians, pescatarians, flexitarians, and omnivores. European Journal of Nutrition, 63(7), 2725-2741. https://doi.org/10.1007/s00394-024-03453-4

Hess, J. M., Robinson, K., & Scheett, A. J. (2025). Vegetarianísh: How "flexitarian" eating patterns are defined and their role in global food-based dietary guidance. Nutrients, 17(14), Article 2369. https://doi.org/10.3390/nu17142369

International Food Information Council. (2024). 2024 IFIC food & health survey. ific.org/wp-content/uploads/2025/07/2024-IFIC-Food-Health-Survey.pdf

Kemper, J. A., & White, S. K. (2021). Young adults' experiences with flexitarianism: The 4Cs. Appetite, 160, Article 105073. https://doi.org/10.1016/j.appet.2020.105073

Kidd, B., Mackay, S., Vandevijvere, S., & Swinburn, B. (2021). Cost and greenhouse gas emissions of current, healthy, flexitarian and vegan diets in Aotearoa (New Zealand). BMJ Nutrition, Prevention & Health, 4(1), 275-284. https://doi.org/10.1136/bmjnph-2021-000262

Lépine, G., Davila, A. M., Cueff, G., Pickering, G., Ichou, F., Perreau, C., Lefranc-Millot, C., Gilles, M., Thirion, F., Mariotti, F., Rémond, D., Fouillet, H., & Polakof, S. (2026). Increasing plant protein sources in the diet modulates gut microbiota and tryptophan metabolism in men at cardiometabolic risk. Gut Microbes, 18(1), Article 2677951. https://doi.org/10.1080/19490976.2026.2677951

Lépine, G., Mariotti, F., Tremblay-Franco, M., Courrent, M., Verny, M. A., David, J., Mathé, V., Jame, P., Anchisi, A., Lefranc-Millot, C., Perreau, C., Guérin-Deremaux, L., Chollet, C., Castelli, F., Chu-Van, E., Huneau, J. F., Rémond, D., Pickering, G., Fouillet, H., & Polakof, S. (2024). Increasing plant protein in the diet induces changes in the plasma metabolome that may be beneficial for metabolic health. A randomized crossover study in males. Clinical Nutrition, 43(12), 146-157. https://doi.org/10.1016/j.clnu.2024.10.009

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

McGraw-Hill. (n.d.). Publisher description for The flexitarian diet: The flexible way to lose weight and be healthier, by Dawn Jackson Blatner. Library of Congress. loc.gov/catdir/enhancements/fy0826/2008004100-d.html

Mihrshahi, S., Ding, D., Gale, J., Allman-Farinelli, M., Banks, E., & Bauman, A. E. (2017). Vegetarian diet and all-cause mortality: Evidence from a large population-based Australian cohort, the 45 and Up Study. Preventive Medicine, 97, 1-7. https://doi.org/10.1016/j.ypmed.2016.12.044

Moore, W. J., McGrievy, M. E., & Turner-McGrievy, G. M. (2015). Dietary adherence and acceptability of five different diets, including vegan and vegetarian diets, for weight loss: The New DIETs study. Eating Behaviors, 19, 33-38. https://doi.org/10.1016/j.eatbeh.2015.06.011

Morton, L., Cameron-Smith, D., Gillies, N., Fraser, K., & Braakhuis, A. (2026). Pasture-raised red meat compared with plant-based meat alternatives within healthy dietary patterns: Effects on polyunsaturated fatty acid status and cardiometabolic health in a randomized dietary intervention. American Journal of Clinical Nutrition. Advance online publication. https://doi.org/10.1016/j.ajcnut.2026.101564

Newby, P. K., Tucker, K. L., & Wolk, A. (2005). Risk of overweight and obesity among semivegetarian, lactovegetarian, and vegan women. American Journal of Clinical Nutrition, 81(6), 1267-1274. https://doi.org/10.1093/ajcn/81.6.1267

NIH Office of Dietary Supplements. (2025a, September 4). Iron: Fact sheet for health professionals. ods.od.nih.gov/factsheets/Iron-HealthProfessional

NIH Office of Dietary Supplements. (2025b, July 2). Vitamin B12: Fact sheet for health professionals. ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional

Orlich, M. J., Singh, P. N., Sabaté, J., Fan, J., Sveen, L., Bennett, H., Knutsen, S. F., Beeson, W. L., Jaceldo-Siegl, K., Butler, T. L., Herring, R. P., & Fraser, G. E. (2015). Vegetarian dietary patterns and the risk of colorectal cancers. JAMA Internal Medicine, 175(5), 767-776. https://doi.org/10.1001/jamainternmed.2015.59

Orlich, M. J., Singh, P. N., Sabaté, J., Jaceldo-Siegl, K., Fan, J., Knutsen, S., Beeson, W. L., & Fraser, G. E. (2013). Vegetarian dietary patterns and mortality in Adventist Health Study 2. JAMA Internal Medicine, 173(13), 1230-1238. https://doi.org/10.1001/jamainternmed.2013.6473

Päivärinta, E., Itkonen, S. T., Pellinen, T., Lehtovirta, M., Erkkola, M., & Pajari, A. M. (2020). Replacing animal-based proteins with plant-based proteins changes the composition of a whole Nordic diet: A randomised clinical trial in healthy Finnish adults. Nutrients, 12(4), Article 943. https://doi.org/10.3390/nu12040943

Pellinen, T., Päivärinta, E., Isotalo, J., Lehtovirta, M., Itkonen, S. T., Korkalo, L., Erkkola, M., & Pajari, A. M. (2022). Replacing dietary animal-source proteins with plant-source proteins changes dietary intake and status of vitamins and minerals in healthy adults: A 12-week randomized controlled trial. European Journal of Nutrition, 61(3), 1391-1404. https://doi.org/10.1007/s00394-021-02729-3

Penniecook-Sawyers, J. A., Jaceldo-Siegl, K., Fan, J., Beeson, L., Knutsen, S., Herring, P., & Fraser, G. E. (2016). Vegetarian dietary patterns and the risk of breast cancer in a low-risk population. British Journal of Nutrition, 115(10), 1790-1797. https://doi.org/10.1017/S0007114516000751

Raj, S., Guest, N. S., Landry, M. J., Mangels, A. R., Pawlak, R., & Rozga, M. (2026). Vegetarian dietary patterns for adults: A position paper of the Academy of Nutrition and Dietetics. Journal of the Academy of Nutrition and Dietetics, 126(3), Article 156227. https://doi.org/10.1016/j.jand.2025.156227

Ribeiro, R. V., Senior, A. M., Simpson, S. J., Tan, J., Raubenheimer, D., Le Couteur, D., Macia, L., Holmes, A., Eberhard, J., O'Sullivan, J., Koay, Y. C., Kanjrawi, A., Yang, J., Kim, T., & Gosby, A. (2024). Rapid benefits in older age from transition to whole food diet regardless of protein source or fat to carbohydrate ratio: A randomised control trial. Aging Cell, 23(11), Article e14276. https://doi.org/10.1111/acel.14276

Rizzo, N. S., Sabaté, J., Jaceldo-Siegl, K., & Fraser, G. E. (2011). Vegetarian dietary patterns are associated with a lower risk of metabolic syndrome: The Adventist Health Study 2. Diabetes Care, 34(5), 1225-1227. https://doi.org/10.2337/dc10-1221

Rolands, M. R., Hackl, L. S., Bochud, M., & Lê, K. A. (2025). Protein adequacy, plant protein proportion, and main plant protein sources consumed across vegan, vegetarian, pescovegetarian, and semivegetarian diets: A systematic review. Journal of Nutrition, 155(1), 153-167. https://doi.org/10.1016/j.tjnut.2024.07.033

Sieke, E. H., Carlson, J. L., Lock, J., Timko, C. A., Neumark-Sztainer, D., & Peebles, R. (2022). To meat or not to meat: Disordered eating and vegetarian status in university students. Eating and Weight Disorders, 27(2), 831-837. https://doi.org/10.1007/s40519-021-01202-8

Springmann, M., Clark, M. A., Rayner, M., Scarborough, P., & Webb, P. (2021). The global and regional costs of healthy and sustainable dietary patterns: A modelling study. Lancet Planetary Health, 5(11), e797-e807. https://doi.org/10.1016/S2542-5196(21)00251-5

Springmann, M., Wiebe, K., Mason-D'Croz, D., Sulser, T. B., Rayner, M., & Scarborough, P. (2018). Health and nutritional aspects of sustainable diet strategies and their association with environmental impacts: A global modelling analysis with country-level detail. Lancet Planetary Health, 2(10), e451-e461. https://doi.org/10.1016/S2542-5196(18)30206-7

Tanous, D. R., Motevalli, M., Leitzmann, C., Wirnitzer, G., Rosemann, T., Knechtle, B., & Wirnitzer, K. (2024). Dietary habits and race day strategies among flexitarian, vegetarian, and vegan recreational endurance runners: A cross-sectional investigation from the NURMI Study (Step 2). Nutrients, 16(11), Article 1647. https://doi.org/10.3390/nu16111647

Tantamango-Bartley, Y., Jaceldo-Siegl, K., Fan, J., & Fraser, G. (2013). Vegetarian diets and the incidence of cancer in a low-risk population. Cancer Epidemiology, Biomarkers & Prevention, 22(2), 286-294. https://doi.org/10.1158/1055-9965.EPI-12-1060

Tantamango-Bartley, Y., Knutsen, S. F., Knutsen, R., Jacobsen, B. K., Fan, J., Beeson, W. L., Sabate, J., Hadley, D., Jaceldo-Siegl, K., Penniecook, J., Herring, P., Butler, T., Bennett, H., & Fraser, G. (2016). Are strict vegetarians protected against prostate cancer? American Journal of Clinical Nutrition, 103(1), 153-160. https://doi.org/10.3945/ajcn.114.106450

Timko, C. A., Hormes, J. M., & Chubski, J. (2012). Will the real vegetarian please stand up? An investigation of dietary restraint and eating disorder symptoms in vegetarians versus non-vegetarians. Appetite, 58(3), 982-990. https://doi.org/10.1016/j.appet.2012.02.005

Tonstad, S., Butler, T., Yan, R., & Fraser, G. E. (2009). Type of vegetarian diet, body weight, and prevalence of type 2 diabetes. Diabetes Care, 32(5), 791-796. https://doi.org/10.2337/dc08-1886

Tonstad, S., Stewart, K., Oda, K., Batech, M., Herring, R. P., & Fraser, G. E. (2013). Vegetarian diets and incidence of diabetes in the Adventist Health Study-2. Nutrition, Metabolism and Cardiovascular Diseases, 23(4), 292-299. https://doi.org/10.1016/j.numecd.2011.07.004

Turner-McGrievy, G. M., Davidson, C. R., Wingard, E. E., Wilcox, S., & Frongillo, E. A. (2015). Comparative effectiveness of plant-based diets for weight loss: A randomized controlled trial of five different diets. Nutrition, 31(2), 350-358. https://doi.org/10.1016/j.nut.2014.09.002

Turner-McGrievy, G. M., Wirth, M. D., Shivappa, N., Wingard, E. E., Fayad, R., Wilcox, S., Frongillo, E. A., & Hébert, J. R. (2015). Randomization to plant-based dietary approaches leads to larger short-term improvements in Dietary Inflammatory Index scores and macronutrient intake compared with diets that contain meat. Nutrition Research, 35(2), 97-106. https://doi.org/10.1016/j.nutres.2014.11.007

Watling, C. Z., Schmidt, J. A., Dunneram, Y., Tong, T. Y. N., Kelly, R. K., Knuppel, A., Travis, R. C., Key, T. J., & Perez-Cornago, A. (2022). Risk of cancer in regular and low meat-eaters, fish-eaters, and vegetarians: A prospective analysis of UK Biobank participants. BMC Medicine, 20(1), Article 73. https://doi.org/10.1186/s12916-022-02256-w

Wozniak, H., Larpin, C., de Mestral, C., Guessous, I., Reny, J. L., & Stringhini, S. (2020). Vegetarian, pescatarian and flexitarian diets: Sociodemographic determinants and association with cardiovascular risk factors in a Swiss urban population. British Journal of Nutrition, 124(8), 844-852. https://doi.org/10.1017/S0007114520001762

Xu, X., Qin, A., & Wang, S. (2026). Flexitarian dietary patterns and neuropsychiatric multimorbidity among the oldest-old in China. Frontiers in Nutrition, 13, Article 1789764. https://doi.org/10.3389/fnut.2026.1789764

Yisahak, S. F., Hinkle, S. N., Mumford, S. L., Li, M., Andriessen, V. C., Grantz, K. L., Zhang, C., & Grewal, J. (2021). Vegetarian diets during pregnancy, and maternal and neonatal outcomes. International Journal of Epidemiology, 50(1), 165-178. https://doi.org/10.1093/ije/dyaa200

Zhu, Y., Ocké, M. C., & de Vet, E. (2025). Prevalence and socio-economic disparities in vegetarianism and flexitarianism over 15 years: The Dutch Lifelines Cohort. European Journal of Public Health, 35(4), 714-719. https://doi.org/10.1093/eurpub/ckaf095

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.

Rows rated with GRADE use 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.

All 8 ratings below are this page's own judgment, using GRADE, assigned from the evidence under the archive's September 28, 2026 decision; the searches for this page did not find a published GRADE rating of any flexitarian or semi-vegetarian outcome. The banner rates death from any cause because longer life is one of the claims in the popular book's subtitle and because it is the outcome with the longest follow-up. Of these, 2 rows are marked provisional: one because a study behind it could be read only as an abstract, and one because its imprecision judgment still needs a valid interval. Each row's reasons say where the rating starts and judge all 5 GRADE domains; where imprecision is judged, the row names the threshold used.

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
Death from any cause (the banner rating)	Very low	This page's own judgment, using GRADE. Semi-vegetarians against people who ate meat more often, in 2 independent cohorts, with 2 reports from Adventist Health Study-2: 88,400 adults over a median of 11.1 years (Abris et al., 2024) and the earlier 5.8-year analysis (Orlich et al., 2013); and the Australian 45 and Up Study, 243,096 adults over a mean of 6.1 years (Mihrshahi et al., 2017).	Cohort studies start at low. Lowered 1 level for risk of bias: diet was measured once by questionnaire at baseline and may have changed over 11 years, and confounding by other health habits cannot be ruled out. Indirectness is also serious: most of the evidence comes from one church-based population, and frequency definitions may not match how people who call themselves flexitarian eat; the rating is at its floor. Inconsistency not serious: the 2 cohorts' estimates, 0.99 and 1.12, have overlapping intervals. Imprecision not serious, judged against a 10 percent difference in death rate, a cautious threshold for death: the 11-year interval, 0.92 to 1.07, lies inside it. Publication bias could not be assessed with 2 cohorts. The rating supports "no clear difference was detected," not that the diets are equivalent.
New type 2 diabetes over 2 years	Very low	This page's own judgment, using GRADE. Semi-vegetarians against nonvegetarians, 41,387 Adventist Health Study-2 participants without diabetes at the start, 2 years; adjusted odds ratio 0.49 (0.31 to 0.76) (Tonstad et al., 2013). The cross-sectional baseline analysis (Tonstad et al., 2009) was read alongside and is not counted as cohort evidence.	Cohort studies start at low. Lowered 1 level for risk of bias: diabetes was self-reported without blood testing, and not everyone returned the follow-up questionnaire. Imprecision is also serious: although the interval lies wholly below the 10 percent threshold used for row 1, it rests on about 22 semi-vegetarians with new diabetes, calculated from the paper's 0.92 percent of 2,404, too few events for a stable estimate; the rating is at its floor. Not raised for a large effect, because the upper end of the interval, 0.76, is a modest effect and confounding is plausible. Indirectness serious for people outside this population. Inconsistency cannot be judged from 1 cohort. Publication bias could not be assessed.
Cancer, all sites, over about 4 years	Very low	This page's own judgment, using GRADE. Semi-vegetarians against nonvegetarians, 69,120 Adventist Health Study-2 participants, 182 cancers among 3,881 semi-vegetarians; hazard ratio 0.98 (0.83 to 1.18) (Tantamango-Bartley et al., 2013). The colorectal, breast and prostate cancer analyses were read alongside.	Cohort studies start at low. Lowered 1 level for risk of bias: diet measured once at baseline, early follow-up. Imprecision is also serious: judged against the 10 percent threshold used for row 1, the interval, from 17 percent lower to 18 percent higher, includes differences beyond it in both directions; the rating is at its floor. Inconsistency cannot be assessed from one independent cohort for all-site cancer. Indirectness serious for people outside this population. Publication bias could not be assessed. No clear difference was detected.
Body weight, as measured, at 6 months	Very low	This page's own judgment, using GRADE. Semi-vegetarian against omnivorous dietary advice, adults with overweight or obesity; 63 randomized across 5 diets, 13 to the semi-vegetarian diet, 50 finishing; -3.2 against -3.1 percent of body weight (Turner-McGrievy, Davidson, et al., 2015). The trial did not report this comparison; this page's approximate 95 percent interval for the difference is -3.2 to +3.0 percentage points.	Randomized trials start at high. Lowered 1 level for risk of bias: participants and staff knew the diet, allocation concealment is not described, the omnivorous control group had fewer meetings, and 4 of 13 semi-vegetarian and 4 of 12 omnivorous participants had no 6-month weight, which was imputed as a gain of 0.3 kg a month (a no-change analysis gave similar results). Lowered 2 levels for very serious imprecision: this page adopts 1 percentage point of body weight as its appraisal threshold, borrowing the step between neighboring groups in the trial's 2-month power calculation, which was not an established clinical threshold for this 6-month comparison; the approximate interval includes larger differences in both directions; the trial was sized to detect about 2.85 points between 2 groups. Indirectness not serious for adults seeking to lose weight. Inconsistency and publication bias cannot be judged from 1 trial. Weight is reported as a measurement, not as a goal.
LDL cholesterol at 12 weeks, provisional (total cholesterol not rated separately)	Low	This page's own judgment, using GRADE. The question rated is what a self-chosen flexitarian diet does to LDL cholesterol. Evidence: a prescribed diet with 30 percent of protein from animal foods against one with 70 percent, close to the usual Finnish diet, in healthy adults; 145 randomized, 136 finishing, 12 weeks; LDL about 0.3 mmol/L lower, read from the paper's figure (Päivärinta et al., 2020).	Randomized trials start at high. Risk of bias not lowered: participants could not be blinded, but the outcome is a laboratory measure and 94 percent finished. Lowered 1 level for indirectness: a prescribed diet with study-supplied protein foods in healthy, well-educated volunteers is not the same as a self-chosen flexitarian diet, and 12 weeks says nothing about longer periods. Lowered 1 level for imprecision as a provisional judgment, against 0.5 mmol/L, the threshold the Whole-Food Plant-Based Diet page uses for LDL. Imprecision remains provisional. The paper reports a baseline-adjusted, Bonferroni-corrected comparison, so its rounded P value cannot be treated as an ordinary unadjusted test to reconstruct the interval used here. The 0.5 mmol/L threshold remains this page's chosen threshold; a valid pairwise interval or a justified information-size calculation is still needed to complete this domain judgment. The paper's figure gives adjusted endpoint means without standard deviations, and lipids were not the outcome the trial's size was planned for; that supports caution but does not replace the calculation. Inconsistency cannot be judged from 1 trial; in the 4-week trial in older adults, a total cholesterol difference did not remain after adjustment. Publication bias could not be assessed.
Vitamin B12 status at 12 weeks	Moderate	This page's own judgment, using GRADE. The question rated is whether a self-chosen flexitarian diet lowers vitamin B12 status. Evidence: the prescribed diet with 30 percent of protein from animal foods, with unfortified plant products, against the 70 percent diet, same trial, 12 weeks, with 44 adults analyzed in the 30 percent group and 46 in the 70 percent group; holotranscobalamin averaged 97.7 against 122.1 pmol/L at 12 weeks (Pellinen et al., 2022).	Randomized trials start at high. Risk of bias not lowered: an objective blood marker with high completion. Lowered 1 level for indirectness: the plant products supplied were not fortified with vitamin B12, and fortified foods or supplements could change the result. Imprecision not lowered: the row rates the direction of change, so the threshold is no difference; the adjusted test (P < 0.001) and this page's approximate interval calculated from unadjusted 12-week endpoint means and standard deviations, about 4 to 45 pmol/L lower, both exclude it. The size of the fall is uncertain. Inconsistency cannot be judged from 1 trial with this comparison; the 10-week New Zealand trial, a different comparison, found the same direction. Publication bias could not be assessed. The rating is for a fall in status, not for deficiency.
Well-being, depression, anxiety, stress and fatigue scores over 10 weeks	Low	This page's own judgment, using GRADE. A flexitarian diet with about 3 servings a week of red meat against a vegetarian diet with plant-based meat alternatives, both on a vegetarian base; 80 healthy young adults in 40 household pairs, randomized as 8 sets, 78 finishing, 10 weeks (Conner et al., 2025).	Randomized trials start at high. Lowered 1 level for risk of bias: participants knew their diet and reported their own mood. The analysis accounted for the randomized sets, and the partial meat industry funding, which the authors state had no influence, is noted rather than counted as a deduction. Lowered 1 level for imprecision, judged against a small standardized difference of 0.2: the standardized intervals for the 10-week average, such as -0.61 to 0.43 for well-being, include differences beyond 0.2 in both directions. Indirectness not serious for this comparison in healthy young adults. Inconsistency and publication bias cannot be judged from 1 trial. No clear difference was detected.
Dietary restraint and eating-disorder questionnaire scores, as an association (provisional)	Very low	This page's own judgment, using GRADE. People who call themselves semi-vegetarian or flexitarian against omnivores, in surveys of young women and university students (Forestell et al., 2012; Sieke et al., 2022; Timko et al., 2012), with a narrative review (Forestell, 2018).	Observational studies start at low. Lowered 1 level for risk of bias: one-time self-report surveys in convenience samples cannot show whether the diet came before the eating concerns, and some questionnaire items score the food avoidance that a meat-reducing diet involves. Inconsistency is also serious: restraint was higher in 2 studies, while Timko and colleagues' second study found little difference from omnivores once those items were considered; the rating is at its floor. Indirectness serious: young women and students, mostly in the United States, and questionnaire scores are not diagnoses. Imprecision not judged: the studies used different scales with no common threshold, and their semi-vegetarian groups were small, 29 to 75 people. Publication bias could not be assessed. Provisional because 1 of the 3 surveys could be read only as an abstract. This is an association that guides what a coach listens for, not evidence that the diet causes disordered eating.
Heart attack, stroke, cancer or death, in trials	Not rated	This page's own judgment. No comparison is possible.	The searches for this page did not identify a randomized trial of a flexitarian or semi-vegetarian diet that measured any of these outcomes. This is a statement about the trials found, not a finding of no effect.

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 6, 2026, after a combined final review of the third batch of 5 archive pages, the plant-based family, the repairs it asked for, a focused recheck and a repair confirmation. Written October 4, 2026. Findings from abstracts are marked where they are used, and 2 ratings are provisional.

Updated October 21, 2026: The American Heart Association is now named as an author of its 2026 dietary guidance statement (Lichtenstein et al., 2026), as the publisher's citation credits it. No content changed.

Next scheduled review: August 2027. Pages built on annual guidance are rechecked each year. The U.S. News pages and the federal fact sheets cited here are updated from time to time and should be rechecked first.

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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.