Very Low Calorie Diets

Diet Reference Archive: medically supervised diet

Very Low Calorie Diets

Eating plans that replace ordinary meals with nutritionally complete formula products, or a small measured set of foods, for a fixed number of weeks, followed by a planned return to everyday food. They are a supervised medical treatment, used mainly to put early type 2 diabetes into remission or to bring about rapid weight loss before surgery.

Family: Therapeutic and elimination diets Promoted by: clinical research groups, health services and the makers of formula products First appeared: the 1970s, as liquid formula diets GRADE: High for type 2 diabetes remission at 12 months versus usual care in adults with recently diagnosed diabetes; Churuangsuk et al. (2022). Low for remission at 5 years in the original DiRECT groups with available data; this page's 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 way of eating, used as a medical treatment, in which ordinary meals are replaced for a set number of weeks by nutritionally complete formula shakes, soups and bars, or occasionally by a small measured set of foods, so that a person takes in far less energy than usual. It ends with a planned, step-by-step return to everyday food. Definitions vary: the National Institute for Health and Care Excellence (NICE), the guideline body for England, calls under 800 calories a day very low and 800 to 1,200 low, while the American Diabetes Association uses the term very low calorie for 800 to 1,000 calories a day.

Does it work? For one purpose, the evidence is strong. In 2 randomized trials of adults with type 2 diabetes diagnosed within the previous few years, a supervised formula program with food reintroduction and support put 46 percent and 61 percent of participants into remission at 12 months, against 4 percent and 12 percent with usual care, and reviewers rated that 12-month result high in certainty. Remission faded: in the larger trial, 36 percent of the program group were in remission at 2 years, and at 5 years, among participants with 5-year data, 10 percent against 5 percent, a difference that could have been chance. Measured body weight was 6 to 9 kilograms lower than in comparison groups at 12 months, and most of that difference had narrowed or gone by 3 to 5 years. Whether these diets prevent heart attacks, strokes or early death has not been established.

Is it safe? Under supervision, most side effects in the trials were mild: constipation, headache, dizziness, tiredness, feeling cold and some hair loss. The serious risks are gallstones, which are more likely with fast weight loss, and the effects of rapid change on medicines: blood pressure can fall too far for someone on blood pressure medicine, and blood sugar can fall too low for someone on insulin or a sulfonylurea. The American Diabetes Association lists electrolyte abnormalities and heart rhythm problems among the complications and advises that these programs run only for a short time under close medical monitoring.

Who should not do it without talking to a doctor or dietitian first? Anyone considering it. This is a treatment that a physician and a dietitian start and supervise, not a diet to begin alone. DiRECT excluded people who were pregnant or planning pregnancy, people taking insulin, people with an eating disorder, and people with advanced kidney disease, a recent heart attack or severe heart failure. For children and teenagers, the studies found for this page were small, and their authors could not judge safety from them.

Related pages: Detoxes and Cleanses, which covers juice cleanses, the Master Cleanse and detox teas, is a separate page; so are Intermittent Fasting, Ketogenic Diet and Low-Carbohydrate Diets. Full list on the archive index.

1. Overview

What you eat

A very low calorie diet has 3 phases, and what a person eats changes with each one. In the first phase, often called total diet replacement, all ordinary food is replaced by formula products: shakes, soups and bars made to supply protein, vitamins, minerals and essential fats in a small number of calories. In DiRECT, the trial behind most of the diabetes evidence on this page, participants took formula products providing 825 to 853 calories a day, with 59 percent of the energy from carbohydrate, 13 percent from fat and 26 percent from protein, for 12 to 20 weeks (Lean et al., 2018). In another trial, participants took 4 formula products a day plus 750 milliliters of skim milk, 2.25 liters of water or other drinks with little or no energy, and a fiber supplement, for 810 calories a day over 8 weeks (Astbury et al., 2018).

The second phase is food reintroduction. Ordinary meals return one at a time over 2 to 8 weeks, while the formula products are reduced, until the person is eating everyday food again (Lean et al., 2018; Astbury et al., 2018). The third phase is maintenance: ordinary food, regular contact with a nurse or dietitian, and in some programs one formula product a day or a short return to the formula if weight is regained (Astbury et al., 2018; Lean et al., 2019).

A few programs use measured portions of ordinary food instead of formula during the first phase, and some trials of the strictest versions used formula diets as low as 400 to 500 calories a day (Churuangsuk et al., 2022). Whatever the version, the person drinks plenty of water. The American Diabetes Association notes that adequate fiber and fluid help prevent and manage constipation on these diets (American Diabetes Association Professional Practice Committee for Diabetes, 2026).

What you avoid or limit

During the formula phase, the rule is strict: no ordinary meals or snacks, and no drinks that carry energy beyond what the program allows. The program defines the products, the number of them each day and the length of the phase, and a person does not add to them or stretch the phase on their own. During reintroduction and maintenance, the limits loosen into an eating plan built around the person's energy needs, which the dietitian designs.

Where it came from

Liquid formula diets of very few calories were in use by the 1970s (Tsai & Wadden, 2006). One commercial program still sold in the United States began in that decade as a 420-calorie formula diet and later added behavioral support and more calories (Ard et al., 2019).

In the late 1970s, deaths among people using "liquid protein" diets drew wide public attention. A 1981 report on 17 people who died suddenly of heart rhythm disturbances, after a median of 5 months on regimens of about 300 to 400 calories a day made up entirely or largely of protein, found that the deaths did not appear to depend on the type of medical supervision, and its authors recommended curtailing such diets until their safety could be established (Sours et al., 1981). A review published the same year of 44 publicized deaths reached a different conclusion. It judged that 32 of the 36 people with enough information had been managed inappropriately, and concluded that the cardiac deaths could not be ascribed to the diet itself; its authors argued for continued use of the diet under proper supervision (Frank et al., 1981).

Current formulas are designed to supply adequate protein and micronutrients during weight loss (Price & Sumithran, 2022), and current guidelines describe these diets as treatments for supervised medical use (National Institute for Health and Care Excellence, 2025; American Diabetes Association Professional Practice Committee for Diabetes, 2026).

The diabetes research came later. In a 2011 study in England, 11 adults with type 2 diabetes ate 600 calories a day for 8 weeks; their fasting blood sugar returned to the normal range within the first week, and the fat content of their livers fell sharply (Lim et al., 2011). That study led to the Diabetes Remission Clinical Trial, known as DiRECT, which tested a formula program inside ordinary family doctors' practices in Scotland and the north of England, recruited its participants between 2014 and 2016, and reported its 12-month results in December 2017 (Lean et al., 2018, 2019). A trial in Qatar, DIADEM-I, followed (Taheri et al., 2020), and in 2020 the National Health Service in England began offering a program based on the same approach (Valabhji et al., 2024).

What the name means, and why the numbers differ

"Very low calorie" is a label with no single number attached, and clients, programs and studies use it loosely. NICE defines a very-low-energy diet, "also known as" a very-low-calorie diet, as under 800 calories a day, and a low-energy or low-calorie diet as 800 to 1,200 calories a day (National Institute for Health and Care Excellence, 2025). The American Diabetes Association describes "very-low-calorie" interventions as usually providing 800 to 1,000 calories a day (American Diabetes Association Professional Practice Committee for Diabetes, 2026). The DiRECT investigators called their 825 to 853 calorie formula a "low energy formula diet" (Lean et al., 2018), while the American Diabetes Association cites the same trial as evidence for very-low-calorie eating patterns (American Diabetes Association Professional Practice Committee for Diabetes, 2026).

This page uses the title the archive index gives it and covers both: supervised formula programs under 800 calories a day, and the closely related programs of about 800 to 1,200 calories that the major diabetes and weight trials tested. Where a number matters, the page gives the number the study used. Juice cleanses, the Master Cleanse and detox teas are not covered here; they are on the separate Detoxes and Cleanses page.

What it claims to do

The strongest claim comes from the researchers who ran the diabetes trials. The DiRECT investigators concluded that "remission of type 2 diabetes is a practical target for primary care" (Lean et al., 2018). The investigators of the trial in Qatar concluded that the program "could allow a large proportion of young individuals with early diabetes to achieve improvements in key cardiometabolic outcomes" (Taheri et al., 2020).

Programs sold for weight loss make claims about weight. In a trial of one such program, funded by the company that owns it, the investigators concluded that the formula program "was more effective with greater sustained weight loss" than a food-based plan (Ard et al., 2019). Section 4 takes these claims one at a time. The remission claim is well supported for the first year in the people the trials enrolled, and less so after that.

What it gets right

For an adult with type 2 diabetes early in its course, this approach has the strongest trial evidence for remission. Among the dietary approaches compared in a 2022 review, formula programs with total diet replacement were the only ones whose remission evidence the reviewers rated high in certainty (Churuangsuk et al., 2022), and DiRECT made remission one of its 2 primary outcomes (Lean et al., 2018). It also comes with structure. The programs that produced the trial results did not hand people a formula and leave them; they reviewed medicines before day 1, measured blood pressure and blood sugar along the way, planned the return to food, and offered support for months afterward (Lean et al., 2018). The guidelines that now mention these diets make that structure a requirement (National Institute for Health and Care Excellence, 2025; American Diabetes Association Professional Practice Committee for Diabetes, 2026).

The maintenance phase is ordinary food, and much of the coaching work happens there. The American Heart Association's features of a heart-healthy pattern, including plenty of vegetables and fruit, mostly whole grains, healthy protein sources, unsaturated fats, minimally processed foods, and less added sugar and sodium, describe a reasonable destination for the eating that follows the formula (Lichtenstein et al., 2026).

How clients describe it, and what it gets confused with

Clients say "I'm on the shakes," "my doctor put me on a liquid diet before my surgery," "I'm doing the 800-calorie plan," or "I'm trying to reverse my diabetes." Any of these can mean a supervised formula program, a partial meal replacement plan with one or two shakes a day, or a plan the client put together from store-bought shakes. Ask which.

It is most often confused with a juice cleanse or detox, which is a different thing with a different evidence base; the Detoxes and Cleanses page covers those. It is also confused with intermittent fasting, which restricts eating on some days or at some hours rather than replacing food for weeks (see the Intermittent Fasting page), and with the very low calorie ketogenic diet, a variant described under common variations below and on the Ketogenic Diet page.

2. In practice

A typical day of eating

During the formula phase, a day is simple and repetitive. It might be a shake in the morning, a soup at midday, a bar in the afternoon and another shake or soup in the evening, with water and other drinks that carry no energy in between. The person eats nothing else. The products are measured so that the day adds up to the program's target, around 800 calories in the trials described on this page (Lean et al., 2018; Astbury et al., 2018).

During food reintroduction, the formula products give way to ordinary meals one meal at a time (Lean et al., 2024). In maintenance, a day looks like an ordinary day of eating built to the person's energy needs. Some programs keep one formula product a day during the first months of maintenance, and some offer a short return to the formula if weight starts to climb (Astbury et al., 2018; Lean et al., 2019).

Cost, products, and who profits

The costs fall into 2 parts: the products and the professional time. In DiRECT, delivering the program cost about 1,223 British pounds per participant over the first year, at 2017 prices. Formula products accounted for 58 percent of that, about 708 pounds, and visits with the nurse or dietitian for 37 percent. Participants needed fewer diabetes and blood pressure medicines, which offset part of the cost, and the extra cost for each additional person in remission at 1 year was about 2,564 pounds (Xin et al., 2019). Those are costs to the British National Health Service under trial conditions, and the authors described them as generous estimates of what the program would cost in routine care (Xin et al., 2019).

In Sweden, a commercial program that offered a 500-calorie formula diet charged participants about 1,300 U.S. dollars, or 1,000 euros, and all participants paid their own fee (Hemmingsson et al., 2012). No source opened for this page gave a current U.S. price for a medically supervised program, which in the United States depends on the clinic, the program and insurance coverage. A pilot study tested a homemade 800-calorie plan as a cheaper alternative to commercial products in 22 people; 12 completed its 48 weeks, and the authors described it as inexpensive (Hickson et al., 2025). A pilot that small does not show that a homemade plan works as well or as safely as a formula program.

Money attaches to the products and the programs. The formula used in DiRECT was donated by Cambridge Weight Plan, and several investigators reported links with that company or with Counterweight, the company whose specialists trained the nurses and dietitians who delivered the program (Lean et al., 2018; Xin et al., 2019). The DROPLET trial of a formula program for adults with obesity was funded in large part by the company that provided it (Astbury et al., 2018).

A U.S. trial that its authors describe as the largest randomized trial of total meal replacement in the United States was funded by Nestlé Health Science, and the paper states that Nestlé Healthcare Nutrition owns the program it tested (Ard et al., 2019). Industry funding does not make a result wrong, and DROPLET's data were analyzed independently by an accredited clinical trials unit (Astbury et al., 2018), but a client who meets these diets through an advertisement is meeting the product, not the trial.

Environmental footprint

The searches run for this page found no study of the environmental footprint of formula diets or very low calorie diets. During the formula phase, a person eats much less food overall, but the products are manufactured and supplied in single-serving sachets (Xin et al., 2019), and no source opened for this page measured the balance. After the formula phase, the footprint depends on the ordinary diet the person returns to, which differs from person to person.

Cultural fit

For the weeks of the formula phase, the diet sets food culture aside entirely, which is its main friction. Shared meals, holidays, celebrations and cooking for a family all continue around a person who is not eating. In interviews with DiRECT participants, starting the formula phase and moving back to food were the hardest points and needed the most support from the nurse or dietitian, although sticking to the formula proved easier than participants had expected (Rehackova et al., 2022).

The trials themselves were drawn from a few populations. DiRECT's participants were typical of Scotland and northeast England, and its authors cautioned that the results could not be applied without qualification to other groups, such as people of South Asian heritage, who tend to develop diabetes with less weight gain (Lean et al., 2018). DIADEM-I enrolled people from the Middle East and north Africa living in Qatar (Taheri et al., 2020). A small trial among 25 adults of South Asian heritage in the United Kingdom found remission rates and acceptability similar to those in mostly white groups (Sattar et al., 2023). The food reintroduction phase is where the person's own food traditions return, and fitting that phase to them is the dietitian's work.

What makes people stop

Most people who start the formula phase in a trial finish it. In DiRECT, 79 percent of the program group completed it; 6 people consented but never took part, and 26 withdrew during the first year, 15 of them during the formula phase (Lean et al., 2018). In a Swedish commercial program with a 500-calorie formula diet, 18 percent had dropped out by 1 year; younger people, people who lost little weight early, and people being treated for depression or psychosis were more likely to stop (Hemmingsson et al., 2012). In a U.S. trial, about a quarter of participants who started left before the end, at similar rates in the formula and food-based groups (Ard et al., 2019).

In the interviews with DiRECT participants, the switch back to ordinary meals was a disruption that people had to adjust to over time, and the researchers concluded that regular, continuing support tailored to the person was central to making the program work (Rehackova et al., 2022).

What happens when you stop

Weight regain after the formula phase is common, and the guidelines say so plainly. NICE advises clinicians to explain to people starting these diets "that weight regain is likely to happen, and if it does it is not because they or their healthcare professional have 'failed'" (National Institute for Health and Care Excellence, 2025).

The trials show what that looks like over time. In DiRECT, average weight in the program group rose by 2.6 kilograms between the first and second years, and about half of the program group needed at least 1 "rescue plan," a short return to the formula, during those 2 years (Lean et al., 2019).

At 5 years, among the program participants with data, average weight was 5.6 kilograms below where it started, against 4.6 kilograms in the comparison group, a difference of 1.1 kilograms that could have been chance (Lean et al., 2024). In DROPLET, the formula group regained an average of 8.9 kilograms between the end of the 6-month program and 3 years, but were still 3.3 kilograms lighter on average than the comparison group at 3 years (Astbury et al., 2021). These figures are weights the studies measured, reported as measurements; the archive does not treat weight change as the measure of whether a diet worked.

Remission follows the same path. In DiRECT, the share of the original program group in remission fell from 46 percent at 1 year to 36 percent at 2 years (Lean et al., 2019), and, among those with data, to 10 percent at 5 years (Lean et al., 2024). Across the whole trial, the chance of being in remission at 2 years was lower the more weight a person had regained between the first and second years (Lean et al., 2019). After the formula phase ends, what helps maintenance has been studied: a review of 20 trials found that meal replacements, weight-loss medicines and higher-protein diets each improved weight maintenance after a very low or low calorie diet, while exercise and dietary supplements did not show a clear effect (Johansson, Neovius, & Hemmingsson, 2014).

Common variations

Low-energy total diet replacement, about 800 to 1,200 calories a day of formula, is the version tested in DiRECT, DIADEM-I and DROPLET (Lean et al., 2018; Churuangsuk et al., 2022; Astbury et al., 2018). The English health service's program begins with a 3-month formula phase (Valabhji et al., 2024). Very low calorie diets in the strict sense, under 800 calories a day and sometimes as low as 400 to 500, were the version used in many older trials and in some commercial programs (Tsai & Wadden, 2006; Hemmingsson et al., 2012).

Food-based versions replace the formula with small measured portions of ordinary food, such as a 600-calorie food-based diet tested in a small single-group study (Churuangsuk et al., 2022) or the homemade 800-calorie plan described above (Hickson et al., 2025). The very low calorie ketogenic diet combines 500 to 800 calories a day with under 50 grams of carbohydrate, and a European obesity association has published guidance on it (Muscogiuri et al., 2021); it is described on the Ketogenic Diet page.

Partial meal replacement replaces 1 or 2 meals a day with a formula product, inside a calorie target of 1,200 to 1,800 calories, as in a large trial of adults with type 2 diabetes in U.S. diabetes centers that a 2022 review describes (Churuangsuk et al., 2022; Lean et al., 2019). Preoperative diets are short formula diets of 2 to 4 weeks before bariatric surgery, used partly to reduce the size of the liver; a review of 4 trials found more weight lost before surgery, and could not establish whether the diets reduced complications after it (McKechnie et al., 2023).

3. For the coach

SCOPE OF PRACTICE

A very low calorie diet is a medical treatment. A health and wellness coach does not prescribe, adjust, endorse or discourage it, and does not diagnose or treat. The decision to start one, the choice of program, the review of every medicine before the first day, and the monitoring along the way belong to a physician and a registered dietitian, inside a supervised program. NICE limits these diets to supervised services with access to a dietitian, for no more than 12 weeks, and the American Diabetes Association says they should be prescribed only to carefully selected people by trained practitioners in medical settings with close monitoring.

When a client is in a supervised program, the coach supports the plan the client and the care team made, and does not change it. When a client plans to replace their meals with shakes on their own, or is already doing so without a clinician, the documented harms on this page apply: the coach's role includes making sure the client has medical oversight, and it does not include supporting the diet itself.

The specific points that need a clinician are any client on insulin, a sulfonylurea, blood pressure medicine or a diuretic; any client who is pregnant, planning pregnancy or breastfeeding; any client under 18; any client with a history of an eating disorder, gallstones, kidney disease or heart disease; and any symptom during the diet that the care team has not already planned for.

Who does what

The physician

Decides whether a very low calorie diet is safe and suitable for this person, and refers them to a supervised program. Reviews every medicine before the first day and changes doses as the diet begins and as weight and blood sugar fall. In DiRECT, the protocol called for planned withdrawal of diabetes and blood pressure medicines on the first day and their reintroduction under a clinician's protocol if blood sugar or blood pressure rose, with exceptions (Lean et al., 2018; Leslie et al., 2021). The medicines that matter most are insulin and sulfonylureas, which can cause low blood sugar; blood pressure medicines and diuretics, because blood pressure falls quickly on these diets; and any medicine the person's other conditions require. Orders and reads the labs, which include HbA1c, kidney function and electrolytes. Decides whether to offer medicine to prevent gallstones, and arranges eye screening for someone with diabetic eye disease. Confirms remission by the agreed definition and arranges at least yearly follow-up afterward (Riddle et al., 2021).

The registered dietitian

Chooses a nutritionally complete formula, or designs a food-based version, and sets the energy target and the length of the formula phase. Manages the common side effects, such as constipation, through fiber and fluid. Designs the food reintroduction, meal by meal, and the long-term eating plan that follows, fitted to the person's food traditions, budget, kitchen and household. Plans what happens if weight is regained. NICE requires access to "an appropriately trained Registered dietitian or registered nutritionist" for every low-energy or very-low-energy diet (National Institute for Health and Care Excellence, 2025).

The health and wellness coach

Helps the client get clear on why they want to do this and what they expect from it. Helps them plan for the parts of life the formula phase disrupts: meals with family, work lunches, celebrations, travel. Helps them prepare questions for the physician and dietitian, and keeps them connected to that team. Supports the habits the maintenance phase depends on; in DiRECT, the more weight people regained after the first year, the less likely they were to be in remission at 2 years (Lean et al., 2019). Notices how the client is coping, physically and emotionally, and holds the referral line when a symptom, a medicine question or distress about eating comes up. And, if weight returns, helps the client hear what NICE tells clinicians to say: that regain is common and is not a personal failure.

What a client bringing this diet needs

Clients bring very low calorie diets for a few kinds of reason. Some have been offered a program by their doctor, often because they have type 2 diabetes and have read or been told that remission is possible. Some need to lose weight before an operation. Others have seen a shake plan advertised, or heard a friend's story, and want to know whether to try it. Each needs something different.

A client already in a supervised program needs help living with it: getting through the first weeks, managing the social side, and above all preparing for the return to food and the long maintenance phase that follows, since remission in DiRECT was tied to how much weight was regained after the first year (Lean et al., 2019). A client considering a program needs a clear look at what it asks of them, including weeks without ordinary meals, frequent appointments and a long maintenance phase, and a path to the clinician who would decide whether it is suitable. A client planning to do it alone with store-bought shakes needs the plain information that the evidence on this page comes from supervised programs that reviewed medicines first, and a conversation about how to get that supervision.

What the coaching conversation offers that a search engine cannot is the fit between this demanding plan and this person's life, and steady support through the maintenance years, when the formula is gone and the work is ordinary.

What to ask

• What have you been told about this program, and what are you hoping it will do for you?
• Who on your care team is supervising it, and what have they said about your medicines?
• What will be hardest about the weeks without ordinary meals, and who around you will be affected?
• When the formula phase ends, what would you like your everyday eating to look like?

Referral red flags

Some of these call for a prompt conversation with the care team, and some for urgent help. A client on insulin or a sulfonylurea who reports feeling shaky, dizzy, lightheaded, confused or irritable may be having a low blood sugar episode right now. The first step is the one in their own diabetes plan, with emergency help if symptoms are severe or they cannot manage the episode themselves; telling the prescriber is the separate step that follows (National Institute of Diabetes and Digestive and Kidney Diseases, n.d.-b). A client with pain in the upper right abdomen lasting several hours, especially with fever, chills, nausea and vomiting, or yellowing of the skin or eyes, should see a doctor right away, because these can be signs of a gallstone complication (National Institute of Diabetes and Digestive and Kidney Diseases, n.d.-c).

A client who feels dizzy or lightheaded, especially on standing, should tell the clinician supervising the diet, who can work out the cause; in DiRECT, about a third of participants reported dizziness during the formula phase, mostly mild (Leslie et al., 2021). A client on any of the medicines named above who is starting a very low calorie diet without having told the prescriber goes back to the prescriber before the diet begins. A client who is pregnant or planning a pregnancy, who is under 18, or who has a history of an eating disorder needs a clinician's assessment before any such diet.

Behavior matters too. A client who is extending the formula phase beyond what the program planned, restarting it repeatedly on their own, skipping the food-reintroduction phase, or describing the diet with fear, guilt or secrecy is worth a careful, open conversation. What the behavior is for, whether it causes distress, and whether it is narrowing the client's life are the questions; a real concern about disordered eating goes through the coach's own referral process, or to the client's clinician under an existing care plan.

Special populations

Pregnancy and breastfeeding

DiRECT excluded people who were pregnant or considering pregnancy (Lean et al., 2018). A review of using these diets to lose weight before pregnancy advises stopping the diet when pregnancy is desired and allowing a period of stable weight before trying to conceive, partly because of uncertainty about exposing an early pregnancy to the ketosis these diets cause; usual folate supplementation before pregnancy is still recommended (Price & Sumithran, 2022). The searches for this page found no study of very low calorie diets during breastfeeding. Any client who is pregnant, planning pregnancy or breastfeeding is referred to the obstetric clinician before any such diet.

Children and adolescents

A review of 24 studies in children and adolescents aged 5 to 18 found substantial short-term weight loss on very low energy programs, but its authors concluded that the studies did not allow conclusions about safety (Andela et al., 2019). In a trial of 141 adolescents aged 13 to 17 with obesity and a related health problem, which began with 4 weeks of a diet of about 800 calories under a specialist team that screened and monitored for depression and disordered eating, symptoms of both decreased on average over the year (Jebeile et al., 2024). During the year, 17 of the 141 adolescents needed additional support or referral for depression or disordered eating, including 7 with new or recurring symptoms. One adolescent was diagnosed with atypical anorexia nervosa and withdrawn 22 weeks into the trial. The study cannot isolate the effect of its initial 4-week very low energy diet phase (Jebeile et al., 2024). These are specialist pediatric treatments. A coach works with the adult in front of them, and a child's eating belongs to the family and the pediatric team.

Older adults

DiRECT enrolled adults up to age 65 (Lean et al., 2018). In a trial in older adults with obesity, 12 weeks of exercise combined with a very low calorie diet produced more weight loss than exercise with other diets, and also a loss of 4.8 percent of lean mass and 1.2 percent of bone mineral density; the trial did not detect a clear difference between the groups in its main measures of physical function (Haywood et al., 2018). Whether that loss of lean mass and bone matters for a particular older person is a question for the physician and dietitian before such a diet begins.

Athletes and people with high activity

The searches for this page found no trial of very low calorie diets in athletes. The programs described on this page were designed and tested for people with obesity or type 2 diabetes, not for people in heavy training, and an athlete who wants to change weight needs a sports dietitian.

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

This is the group for whom a very low calorie diet changes the most. In DiRECT, the protocol called for clinician-led withdrawal of diabetes and blood pressure medicines at the start, with monitoring and a plan to restart them, because blood pressure falls quickly on these diets and the investigators wanted to avoid dizziness on standing (Lean et al., 2018; Leslie et al., 2021). Some blood pressure medicines were continued for clinical reasons: of the 78 program participants taking them, 65 stopped all of them at the start, 4 stopped some and 9 stopped none. Among the 69 participants who stopped some or all blood pressure medicines, two thirds needed treatment restarted during follow-up, more often those who had been taking 2 or more (Leslie et al., 2021). In another trial, family doctors were given guidance to reduce or stop diabetes and blood pressure medicines at the start of the diet and to review people after 4 weeks (Astbury et al., 2018). Insulin, sulfonylureas and meglitinides can cause low blood sugar, and eating less carbohydrate than usual can bring it on (National Institute of Diabetes and Digestive and Kidney Diseases, n.d.-b). The searches for this page found no study of these diets in people taking warfarin; any change of this size in eating is one the prescriber should know about first. The standing rule is that the prescriber is involved before the diet starts, and in a supervised program that review is part of the program.

People with a history of disordered eating

The trials and guidelines treat a possible eating disorder as a reason for assessment before any such diet. DiRECT excluded people with an eating disorder or purging behavior (Lean et al., 2018), and NICE advises offering "assessment and counselling if they may have eating disorders or other mental health issues, to ensure the diet is appropriate for them" (National Institute for Health and Care Excellence, 2025). Among 580 people enrolled in the English health service's program, 26 percent screened positive for possible binge eating disorder before starting, a rate the authors judged higher than in the general public (Marwood et al., 2025). In a small trial of 56 adults with type 2 diabetes who already had eating disorder symptoms, a supervised formula program with behavioral support met the trial's noninferiority criterion for average eating disorder symptom scores at 6 months, and no new eating disorder was suspected (Tsompanaki et al., 2025). ARIADNE excluded people who reported a current or previous diagnosis of an eating disorder and people whose combined screening scores for eating disorder symptoms and related impairment were high enough to suggest an eating disorder was likely present (Tsompanaki et al., 2025; University of Oxford, 2025). Its finding concerns average symptom scores in a small, selected, supported program; it does not establish safety for the groups it excluded. These findings come from supervised programs that screened and monitored people. For a client with a history of disordered eating, any such diet is a decision for their clinician within their existing care plan.

Client misconceptions

Three come up most. That buying shakes and drinking them instead of meals is the same thing as the programs in the research, when the trials supervised medicines, monitored people and planned the return to food. That remission means diabetes is cured, when the international definition calls it remission precisely because it may not last, and people in remission still need yearly checks (Riddle et al., 2021). And that the weight always comes back so there is no point, when the trials show partial regain on average, with some people keeping much of their loss and some remaining in remission for years. Each is taken up in section 6.

🤝 COACHING CONNECTION

Denise, 54, has type 2 diabetes and tells her coach that her doctor has offered her a place in a 12-week shake program, starting next month. She is excited and also worried about her daughter's wedding in the middle of it. The coach asks what her doctor said about the program and what she hopes it will do for her. Denise says she wants to come off her diabetes tablets if she can. The coach asks what she would like the wedding day to look like, and Denise decides to ask the program dietitian how others have handled a big event. The coach asks what she knows about the plan for her tablets, and Denise realizes she does not know whether to keep taking them; she writes that down as her first question for the clinic. The coach gives no advice about her food or her medicine.

4. The evidence

(select the heading to open or close this section)

The best evidence for very low calorie diets comes from randomized trials of supervised formula programs in adults with type 2 diabetes of short duration, and it shows a large effect on diabetes remission at 1 year, which reviewers rated high in certainty. The effect shrinks over the following years, and by 5 years the one trial with that follow-up could no longer distinguish its program group from its comparison group on remission.

Trials in adults with obesity, with and without diabetes, show more weight lost at 1 year than with usual care, with much of the difference gone by 3 to 5 years. No trial found for this page was designed or large enough to show whether these diets prevent heart attacks, strokes or early death, and the known harms, chiefly gallstones and the effects of rapid change on medicines, come from trials and from a large observational study.

Evidence from randomized controlled trials

A trial assigns people to a program by chance and compares them with people assigned to something else, which is the strongest way to test whether the program itself causes a result. The trials of very low calorie diets cannot hide from participants which group they are in, and the outcomes that matter most here, HbA1c, medicine use and measured weight, are recorded objectively, which limits the bias that knowledge of the assignment can introduce. Each trial below tested a whole program: the formula phase, the return to food, and months of support. None isolates the formula from the support around it.

Cardiometabolic outcomes

Type 2 diabetes remission in DiRECT. The Diabetes Remission Clinical Trial randomized 49 family doctors' practices in Scotland and the Tyneside region of England, so that everyone in a practice received the same care, and enrolled 306 adults aged 20 to 65 who had been diagnosed with type 2 diabetes within the previous 6 years, had a body mass index of 27 to 45 and were not taking insulin; 149 in each group made up the main analysis. The program called for planned withdrawal of diabetes and blood pressure medicines on the first day and their reintroduction under a clinician's protocol, with exceptions; the program group took a formula diet of 825 to 853 calories a day for 3 to 5 months, returned to food over 2 to 8 weeks, and then had monthly support. The comparison group received best-practice diabetes care under national guidelines (Lean et al., 2018).

Remission was defined as an HbA1c below 6.5 percent after at least 2 months off all diabetes medicines. At 12 months, 68 of 149 people in the program group (46 percent) were in remission, against 6 of 149 (4 percent) in the comparison group, an odds ratio of 19.7, with a 95 percent confidence interval of 7.8 to 49.8. These are crude proportions at a single point, with anyone missing counted as not in remission. Quality of life, measured on a 100-point scale, improved by 7.2 points in the program group and fell by 2.9 in the comparison group (Lean et al., 2018).

Remission tracked weight change across the whole trial. None of the 76 people who gained weight were in remission at 12 months, against 7 percent of those who lost up to 5 kilograms, 34 percent of those who lost 5 to 10 kilograms, 57 percent of those who lost 10 to 15 kilograms, and 86 percent of those who lost 15 kilograms or more (Lean et al., 2018). That is an association within the trial, not a randomized comparison, and the people who lost the most may have differed in other ways from those who lost the least.

Remission at 2 and 5 years. At 2 years, 53 of 149 in the program group (36 percent) were in remission, against 5 of 149 (3 percent), an odds ratio of 25.8, from 8.3 to 80.8. HbA1c was 4.8 mmol/mol lower in the program group, despite less than half as much use of diabetes medicines, and systolic blood pressure was 3.4 mm Hg lower with fewer people on blood pressure medicine (Lean et al., 2019). The 2-year figures were checked against the publisher-formatted version of the paper published online in March 2019.

After 2 years, the trial became an extension study. All participants and their doctors were told the results and encouraged to work on their weight, so the comparison group was no longer receiving usual care; 95 of the 101 program participants still engaged joined a lower-intensity extension, and the others were followed through health records. At 5 years, among people with data, 12 of 118 in the original program group (10 percent) and 5 of 93 in the original comparison group (5 percent) were in remission, an odds ratio of 2.0, from 0.6 to 7.5, a difference the trial could not distinguish from chance. Of the extension participants who had been in remission at 2 years and were followed, 11 of 43 (26 percent) were still in remission at 5 years (Lean et al., 2024).

At 5 years, no clear difference in HbA1c was detected between the original groups, but the program group had spent more of the 5 years off diabetes medicines, and 32 percent were off them at 5 years against 13 percent in the comparison group. These 5-year figures use the data available without assumptions about missing data, the extension group chose itself by staying engaged, and the authors cautioned that differences after 2 years might not reflect the intervention (Lean et al., 2024).

Remission in other trials. DIADEM-I in Qatar randomized 158 adults aged 18 to 50 from the Middle East and north Africa who had had type 2 diabetes for 3 years or less and a body mass index of 27 or more. At 12 months, 61 percent of the program group and 12 percent of the usual care group were in remission, an odds ratio of 12.0, from 5.2 to 28.0; remission was a key secondary outcome, and the main outcome was weight (Taheri et al., 2020). The full published report of this trial was read for this page. A small trial among 25 adults of South Asian heritage in the United Kingdom found remission in 5 of 13 who started the formula phase straight away, against 0 of 12 who waited (Sattar et al., 2023).

A 2022 review rated the evidence that formula total diet replacement programs increase remission at 12 months, compared with usual care, high in certainty using GRADE, from DiRECT and DIADEM-I together, 445 participants. The review describes both trials as designed with remission as the primary outcome; DIADEM-I's own report names weight as its primary outcome and remission as a key secondary one (Churuangsuk et al., 2022; Taheri et al., 2020).

Remission outside trials. The English health service's program, delivered at scale since 2020 to adults aged 18 to 65 diagnosed within 6 years, reported early results in 2024. Of 1,740 people who started the formula phase before 2022, 55 percent completed the 12-month program. Among the 710 who started and had the 2 HbA1c tests the definition required, 27 percent were in remission at 1 year, a lower rate than in the trials, and the authors noted that data were more limited outside research (Valabhji et al., 2024). Only the abstract of this evaluation was read for this page.

Blood pressure, lipids and other measures. In DiRECT, blood pressure fell quickly once the formula phase began, which is why the protocol called for withdrawing blood pressure medicines at the start. Of the 69 program participants who stopped some or all of them, about a quarter needed one restarted during the formula phase and two thirds at some point over 2 years (Leslie et al., 2021). Triglycerides fell more in the program group at 2 years (Lean et al., 2019). In DROPLET, a trial in adults with obesity, the formula group had larger falls in HbA1c, diastolic blood pressure and triglycerides at 1 year, with no clear difference in systolic blood pressure or LDL cholesterol (Astbury et al., 2018).

Heart attacks, strokes and serious adverse events

No trial found for this page was designed or large enough to show whether a very low calorie diet prevents heart attacks, strokes or deaths. DiRECT recorded serious adverse events from medical records as a safety measure. In the second year, there were 9 in the program group and 22 in the comparison group, including several vascular events in the comparison group (Lean et al., 2019), and over 5 years the rate of serious adverse events in the original program group was about half that in the comparison group, 4.8 against 10.2 per 100 person-years (Lean et al., 2024). The authors noted that the trial was not powered for these outcomes, and a difference in serious adverse events is not evidence that the diet prevents disease.

Cancer

The supervised continuous formula programs reviewed here do not establish prevention of cancer or an effect on cancer treatment outcomes. Trials of short cyclic fasting-mimicking diets concern a different intervention, outside this page's scope.

Body weight, as measured

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. For these diets, weight is unavoidable: the programs were built to produce rapid weight loss, and remission in the diabetes trials followed it.

At 12 months in DiRECT, average weight had fallen by 10.0 kilograms in the program group and 1.0 kilogram in the comparison group, an adjusted difference of 8.8 kilograms, from 7.3 to 10.3 (Lean et al., 2018). In DIADEM-I, the difference was 6.1 kilograms, from 3.8 to 8.4 (Taheri et al., 2020). In DROPLET, 278 adults with obesity, 15 percent of whom had diabetes, were randomized to a formula program providing 810 calories a day for 8 weeks or to usual weight-loss support from a practice nurse; at 12 months, the formula group weighed 7.2 kilograms less on average, from 4.9 to 9.4 (Astbury et al., 2018).

A U.S. trial of a formula program funded by its owner found weight 10.5 percent lower than at the start at 52 weeks, against 5.5 percent with a food-based program (Ard et al., 2019). A review of trials comparing very low energy diets plus behavioral support with behavioral programs alone found 3.9 kilograms more weight lost at 1 year, 1.4 kilograms more at 2 years, and 1.3 kilograms more at 3 to 5 years, where the interval included no difference (Parretti et al., 2016); only the abstract of that review was read.

Longer follow-up shows the difference narrowing. In DROPLET at 3 years, with 66 percent of participants measured, the difference was 3.3 kilograms, from 1.5 to 5.2 (Astbury et al., 2021). In DiRECT at 5 years, with data from 78 percent of the program group and 55 percent of the comparison group, the difference was 1.1 kilograms and the interval included no difference (Lean et al., 2024).

Mortality

The searches for this page found no randomized trial of a very low calorie diet that was designed to measure death from any cause or from a specific cause, and the deaths recorded in the trials reviewed were too few to estimate an effect.

Eating behavior and wellbeing

A 2022 review of 35 publications on formula total diet replacement programs found no marked harm to mental well-being, and improvements in depression, anxiety and stress scores after the formula phase, mostly in studies without a comparison group; the 2 analyses that compared formula programs with food-based diets did not detect a clear difference in depression, with too little statistical power to be sure (Harris et al., 2022).

In the ARIADNE trial, 56 adults with type 2 diabetes and existing eating disorder symptoms were randomized to a supervised formula program or usual care. The program met the trial's noninferiority criterion for average eating disorder symptom scores at 6 months, and no participant was suspected of developing a new eating disorder (Tsompanaki et al., 2025).

All 56 were analyzed in the groups they were assigned to, but 6-month questionnaires were returned by 22 of 28 in the program group and 27 of 28 with usual care. A worst-case analysis that assumed symptoms had worsened in everyone with missing answers in the program group still met the noninferiority criterion. Average symptom scores also fell more in the program group, a difference of 0.8 points on a scale of 0 to 6 (95% confidence interval 0.3 to 1.4), and the difference was still present at 12 months. One serious adverse event, a gallbladder removal, occurred in the program group in a participant who had stopped the program more than 6 months earlier (Tsompanaki et al., 2025).

In DiRECT, quality of life was higher in the program group at 12 and 24 months (Lean et al., 2018, 2019).

Evidence from long-term prospective cohort studies

A cohort study follows people who already made a choice and records what happens to them. It can show that a choice goes with an outcome; it cannot by itself show that the choice caused it. For very low calorie diets, the searches for this page found no long-term cohort study of heart disease, cancer or death. The cohort evidence that exists comes from a Swedish commercial weight-loss program whose records were linked to national health registers, and it answers 2 practical questions: how much weight people lost and kept off, and how often they developed gallstones.

Cardiometabolic outcomes

The searches for this page found no cohort study of cardiometabolic disease outcomes after a very low calorie diet. The cardiometabolic evidence on this page comes from the trials above.

Cancer

The searches for this page found no cohort study of cancer outcomes after a very low calorie diet.

Body weight, as measured

Among 9,037 adults in the Swedish commercial program, those who chose a 500-calorie formula diet had lost 11.4 kilograms on average after 1 year, against 6.8 kilograms with a 1,200 to 1,500 calorie diet combining formula and food, and 5.1 kilograms with a restricted diet of ordinary food; after adjustment, the formula group lost 2.8 kilograms more than the low calorie group (Hemmingsson et al., 2012). People chose their own diet, so the groups differed at the start: the formula group had a higher body mass index on average. Only the abstract was read for this page.

Gallstones

The same program provided the clearest estimate of the main physical harm. Researchers matched 3,320 people who started the 500-calorie formula diet with 3,320 similar people who started the 1,200 to 1,500 calorie diet, by age, sex, body mass index, waist size and gallstone history, and followed them for 1 year through national hospital records. Gallstones that needed hospital care occurred in 48 people in the very low calorie group and 14 in the low calorie group, a rate of 152 against 44 per 10,000 person-years. That is a hazard ratio of 3.4, from 1.8 to 6.3, a time-to-event estimate, or about 1 additional case for every 92 people treated over the year (Johansson, Sundström, et al., 2014).

Surgery to remove the gallbladder followed in 29 and 9 people. Allowing for the weight lost in the first 3 months reduced the hazard ratio for gallstones to 2.5, from 1.3 to 5.1, which suggests that part of the difference reflects the faster weight loss. The authors called the risk low in absolute terms and about 3 times higher with the very low calorie diet (Johansson, Sundström, et al., 2014).

Mortality

The searches for this page found no cohort study of death after a supervised very low calorie diet. One cohort study of 6,770 U.S. adults found that people who reported drinking meal-replacement products daily or weekly had higher death rates over a median of 14 years than people who seldom did (Zhao et al., 2024). That study measured how often people drank such products in everyday life, not a supervised formula program, and as an observational study it cannot show that the products caused the deaths; only its abstract was read for this page.

Highlighted studies

These 4 sources carry the most weight for this diet. Each is described so that a reader can judge it without opening the paper. The limitation column gives the one weakness that most affects how far the finding can be trusted.

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

Highlighted studies for Very Low Calorie Diets

Study	Design	Sample size	Duration	Finding	The limitation that matters
Lean et al., 2018 and 2019, DiRECT	Cluster-randomized controlled trial in 49 family practices; formula diet of 825 to 853 calories a day for 3 to 5 months, food reintroduction and monthly support, against best-practice diabetes care	306 adults aged 20 to 65 with type 2 diabetes diagnosed within 6 years, body mass index 27 to 45, not on insulin; 149 per group analyzed	2 years	Remission at 12 months in 46 percent against 4 percent, and at 2 years in 36 percent against 3 percent; weight 8.8 kilograms lower than the comparison group at 12 months	Open label, in 2 regions of the United Kingdom, in people early in diabetes; it tests the whole program, so it cannot separate the formula from the support, and its results do not transfer directly to people with longer-standing diabetes or on insulin
Lean et al., 2024, DiRECT extension	Follow-up of the randomized groups to 5 years, with a self-selected extension group receiving low-intensity support	298 randomized; data at 5 years for 118 and 93 people for remission	5 years	Remission at 5 years in 10 percent of the original program group against 5 percent of the comparison group, a difference that could have been chance; 26 percent of those in remission at 2 years and followed were still in remission	After 2 years the comparison group was told the results and encouraged to lose weight, and many people had missing data, so the 5-year comparison is no longer a clean randomized test
Astbury et al., 2018 and 2021, DROPLET	Pragmatic randomized controlled trial in 10 family practices; 810 calories a day of formula for 8 weeks with behavioral support, against usual nurse-led weight support	278 adults with obesity, 15 percent with diabetes	1 year, extended to 3 years	Weight 7.2 kilograms lower than usual care at 1 year and 3.3 kilograms lower at 3 years; adverse events more common in the formula group but mostly mild	Funded largely by the company that provided the program, open label, and only 66 percent of participants were measured at 3 years
Johansson, Sundström, et al., 2014	Matched cohort study within a Swedish commercial weight-loss program, linked to national hospital records	6,640 adults, 3,320 per diet	1 year	Gallstones needing hospital care about 3 times as common with a 500-calorie formula diet as with a 1,200 to 1,500 calorie diet, 152 against 44 per 10,000 person-years	Observational: people chose their own diet, and although they were matched on key traits, other differences between the groups could account for part of the risk

Head to head

The most direct comparison is between very low calorie diets and the less restrictive low calorie diets. A 2006 review of 6 randomized trials found that very low calorie diets produced much larger short-term weight loss, 16.1 percent of starting weight against 9.7 percent, but long-term losses of 6.3 percent against 5.0 percent, a difference that was not statistically significant; dropout was similar (Tsai & Wadden, 2006). Only the abstract was read. In adults with type 2 diabetes, a 2022 umbrella review reported that very low energy diets of 400 to 500 calories a day for 8 to 12 weeks produced 6.6 kilograms more weight loss than diets of 1,000 to 1,500 calories at 3 months, from 3.7 to 9.5, among people who completed 2 small trials, and rated that evidence low in certainty using GRADE (Churuangsuk et al., 2022; see the review record).

The same review compared diet types for diabetes remission at 1 year: formula total diet replacement programs, at a median of 54 percent, rated high in certainty; a meal replacement program, at 11 percent; a Mediterranean diet, at 15 percent, rated low; and a ketogenic diet studied without randomization, at 20 percent, rated very low (Churuangsuk et al., 2022). These are not head-to-head trials: each figure comes from different studies in different people against different comparisons, so they cannot rank the diets. The review's text and its summary table give different certainty ratings for the meal replacement result, so this page does not use that rating. Ketogenic and low-carbohydrate eating are the subjects of the Ketogenic Diet and Low-Carbohydrate Diets pages in this archive.

Where the evidence is absent

The trials reviewed for this page do not establish whether very low calorie diets prevent heart attacks, strokes, cancer or early death; none was designed or large enough to estimate a reliable effect on those outcomes. The strong remission evidence comes from adults aged up to 65, diagnosed within 6 years, with a body mass index of 27 or more in the main trials, and mostly from Scotland, northeast England and Qatar. Most of the strong remission evidence comes from people not taking insulin. DiRECT excluded insulin users; DIADEM-I included one, which provides too little evidence to establish effects for people taking insulin (Lean et al., 2018; Taheri et al., 2020).

People with longer-standing diabetes and people with a lower body mass index were outside those trials; a study of 20 people with a body mass index under 27 found remission in 14 after repeated cycles of 5 percent weight loss, but it had no comparison group (Taylor et al., 2023).

The searches for this page found no trial in athletes, no study during breastfeeding, and no study in people taking warfarin. Evidence in children and adolescents comes from small studies from which their reviewers could draw no conclusions about safety, and from one trial in adolescents under specialist care. Evidence in older adults comes from small trials. Evidence on eating disorders comes from programs that screened participants and from one small trial. Beyond 5 years, the searches found no randomized follow-up of remission, and the long-term effect of repeated rounds of these diets, which NICE lists as weight cycling, was not studied in the sources found (National Institute for Health and Care Excellence, 2025).

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 first mechanism is simple energy balance. Supplying far less energy than the body uses produces rapid weight loss, mostly in the first weeks: in DiRECT, people who took part in the formula phase lost 14.5 kilograms on average during it, then regained about 1 kilogram during food reintroduction and about 2 more during the rest of the first year (Lean et al., 2018).

The second is the response of blood sugar control. In a small study of 11 adults with type 2 diabetes who ate 600 calories a day for 8 weeks, fasting blood sugar fell into the normal range within 1 week, the liver's response to insulin improved, the fat content of the liver fell from about 13 percent to about 3 percent, and the pancreas's early burst of insulin after a meal recovered toward the level seen in people without diabetes (Lim et al., 2011). Those measurements were made in people, but in a small group without a comparison diet, and they show what changed, not that each change caused the next.

The third is blood pressure. Blood pressure falls quickly on these diets, faster than the reduced salt intake alone would explain, according to the DiRECT investigators, which is why blood pressure medicines are reviewed before the first day (Lean et al., 2018; Leslie et al., 2021).

Proposed mechanisms

The DiRECT investigators explain remission through what they call the twin cycle hypothesis: that type 2 diabetes is driven by excess fat inside the liver and the pancreas, and that losing enough weight to clear that fat lets the insulin-producing cells recover (Lean et al., 2018). A related idea, the personal fat threshold, proposes that each person has their own limit for safe fat storage, so that people with diabetes at a body mass index considered normal can also reach remission by losing weight; a study of 20 such people reported results consistent with it, without a comparison group (Taylor et al., 2023).

These are hypotheses from one research group, supported by its own imaging studies, and they do not support any claim in section 4 on their own. Why remission fades over time is not established; weight regain is the factor the trials link most closely to it (Lean et al., 2019).

Gallstones are thought to form during rapid weight loss because the liver releases extra cholesterol into the bile and because fast weight loss can keep the gallbladder from emptying properly (National Institute of Diabetes and Digestive and Kidney Diseases, n.d.-a). A meta-analysis of trials found fewer gallstones during weight loss with the medicine ursodeoxycholic acid and with weight-loss diets higher in fat; the findings held in trials at low risk of bias but were not confirmed by the authors' sequential analysis (Stokes et al., 2014). Only the abstract was read, and whether to prescribe that medicine is the physician's decision.

6. Risks, contraindications and myths

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Warnings from professional or regulatory bodies

NICE, the guideline body for England, states: "Do not use low-energy diets or very-low-energy diets as a long-term strategy to manage obesity." It limits very-low-energy diets to people "living with obesity" who "have a clinically assessed need to lose weight rapidly (for example, to make surgery safer and more feasible)," within a specialist service, and requires that any such diet be nutritionally complete, last "no more than 12 weeks," and include "ongoing clinical support and supervision" (National Institute for Health and Care Excellence, 2025).

The American Diabetes Association states that very-low-calorie interventions "should be provided only by trained and experienced professionals in medical settings with close ongoing monitoring and integration with behavioral support and counseling, and only for a short term (generally up to 3 months)," and that "due to the high risk of complications (electrolyte abnormalities, severe fatigue, cardiac arrhythmias, etc.), very-low-calorie intensive interventions should be prescribed only to carefully selected individuals" (American Diabetes Association Professional Practice Committee for Diabetes, 2026). The 2 bodies differ in where they draw the line, and both agree that this is a supervised, short-term treatment.

Nutrient gaps

A nutritionally complete formula is designed to cover protein, vitamins and minerals during the formula phase (Price & Sumithran, 2022), and NICE requires that any such diet be nutritionally complete (National Institute for Health and Care Excellence, 2025). Plans a person assembles on their own, from a few foods or from products not designed as a sole source of nutrition, carry no such design, and no source opened for this page measured their nutrient content. In a trial in older adults on a formula diet, measures such as vitamin B12, vitamin D, ferritin and folate improved (Haywood et al., 2018).

Constipation was the most common side effect in the trials, and programs add fiber and fluid to manage it (Astbury et al., 2018; American Diabetes Association Professional Practice Committee for Diabetes, 2026). Loss of lean mass and bone density alongside fat loss was measured in older adults and is discussed under special populations (Haywood et al., 2018).

Who should not follow it without medical supervision

Everyone, because the diet is a supervised treatment by definition in the guidelines quoted above. Beyond that, DiRECT excluded people for whom it could carry particular risk: people taking insulin; people with advanced kidney disease, severe or unstable heart failure, or a heart attack in the previous 6 months; people with an eating disorder or purging behavior; people who are pregnant or considering pregnancy; people with a recent hospital admission for depression or taking antipsychotic medicines; and people with substance use problems (Lean et al., 2018). People with gallstones before the diet are more likely to have gallstone problems during it (National Institute of Diabetes and Digestive and Kidney Diseases, n.d.-a). Children and adolescents, older adults, and people taking medicines for diabetes or blood pressure need the specialist and prescriber involvement described in section 3.

Medication interactions

A coach never adjusts medication. The point of knowing these is to know when to send a client back to the prescriber. Insulin, sulfonylureas and meglitinides can cause low blood sugar, and eating less carbohydrate than usual can bring it on (National Institute of Diabetes and Digestive and Kidney Diseases, n.d.-b). Blood pressure medicines and diuretics can let blood pressure fall too far as it drops on the diet, which is why DiRECT planned their withdrawal on the first day and their reintroduction under a clinician's protocol, with exceptions (Lean et al., 2018; Leslie et al., 2021). NICE asks clinicians to "review any medicines they are taking and discuss any changes that may need to be made" before such a diet starts (National Institute for Health and Care Excellence, 2025). For any other regular medicine, the prescriber is the person to ask, before the diet begins.

Signs it is going wrong

Physical signs a coach or a family member might notice include shakiness, dizziness or confusion in someone on insulin or a sulfonylurea, which may be low blood sugar happening now and calls for the person's own treatment plan first, with emergency help if symptoms are severe or the person cannot manage the episode, followed by telling the prescriber (National Institute of Diabetes and Digestive and Kidney Diseases, n.d.-b); dizziness or lightheadedness on standing; severe tiredness; and pain in the upper right abdomen, fever or yellowing of the skin or eyes, which call for a doctor right away (National Institute of Diabetes and Digestive and Kidney Diseases, n.d.-c). Weight a client loses without meaning to, outside a planned program, is also a reason to involve a clinician; it is never a goal or a sign that a diet is working.

Behavioral signs include extending the formula phase beyond the program's plan, starting it again and again without supervision, skipping the return to food, hiding what is being eaten or not eaten, or withdrawing from meals with other people beyond what the program requires. Some of these, such as not eating at a family meal during a planned formula phase, are what the program asks for, so on their own they tell a coach little. The questions are what the behavior is for, whether it causes distress, whether it is narrowing the person's life, and whether it continues after the program ends. None of this is a diagnosis. Where the answers raise a real concern, the coach follows their own referral process.

Myths and where they came from

Myth: "Drinking shakes instead of meals is the same as the programs in the research."

Where it came from: the formula is the most visible part of these programs, and products that look much like it are easy to buy. What is true: the trials tested whole supervised programs that stopped or adjusted medicines on the first day, measured blood pressure and blood sugar, planned the return to food and provided months of support (Lean et al., 2018; Leslie et al., 2021), and the guidelines make that supervision a requirement (National Institute for Health and Care Excellence, 2025; American Diabetes Association Professional Practice Committee for Diabetes, 2026).

Myth: "If my diabetes goes into remission, it is cured."

Where it came from: the trials' striking results, and words such as "reversal" and "cure" that have been used for them (Riddle et al., 2021). What is true: an international consensus chose the word remission because the improvement may not last, defined it as an HbA1c below 6.5 percent for at least 3 months without diabetes medicines, and advised at least yearly HbA1c testing and continued eye, kidney and foot checks for people in remission (Riddle et al., 2021). In DiRECT, remission fell from 46 percent of the program group at 1 year to 10 percent of those with data at 5 years (Lean et al., 2018, 2024).

Myth: "The weight always comes back, so there is no point."

Where it came from: older reviews in which very low calorie diets did not demonstrate greater long-term weight loss than less restrictive diets (Tsai & Wadden, 2006), and the common experience of regain. What is true: regain is common and NICE says it is not a personal failure (National Institute for Health and Care Excellence, 2025), but in the trials it was partial on average; at 3 years, DROPLET's formula group still weighed 3.3 kilograms less than its comparison group (Astbury et al., 2021), and in DiRECT, 11 of 43 people in remission at 2 years and followed were still in remission at 5 years (Lean et al., 2024).

Myth: "A juice cleanse or a detox is a gentler version of the same thing."

Where it came from: both involve drinking in place of eating for a period. What is true: the programs on this page use nutritionally complete formulas under clinical supervision for a specific medical purpose (National Institute for Health and Care Excellence, 2025). Juice cleanses and detox products are a different subject with a different evidence base, covered on the Detoxes and Cleanses page.

7. Key terms

Total diet replacement

A phase of a supervised program in which all ordinary food is replaced by nutritionally complete formula products for a set number of weeks.

Very-low-energy diet and low-energy diet

NICE's terms for diets of under 800 calories a day and of 800 to 1,200 calories a day; the American Diabetes Association uses "very-low-calorie" for 800 to 1,000 calories a day.

Food reintroduction

The planned, step-by-step return to ordinary meals after the formula phase, usually over 2 to 8 weeks.

Type 2 diabetes remission

An HbA1c below 6.5 percent for at least 3 months without any diabetes medicine, under the international consensus definition; it is not a cure, and people in remission still need regular checks.

HbA1c

A blood test that reflects average blood sugar over the previous several months, reported as a percentage or in mmol/mol.

Cluster-randomized trial

A trial that assigns groups, such as whole medical practices, rather than individual people, to each arm, so that everyone in a group receives the same care.

Odds ratio

A way of comparing how likely an outcome is in 2 groups; an odds ratio above 1 means the outcome was more likely in the first group. It is not the same as how many times more people had the outcome.

Hazard ratio

A comparison of how quickly an outcome occurs over time in 2 groups; a hazard ratio of 3.4 means the outcome occurred at about 3.4 times the rate in the first group during follow-up.

Weight cycling

Repeatedly losing and regaining weight, which NICE lists among the risks to explain before a low-energy or very-low-energy diet begins.

GRADE

The 4-level scale used in clinical guidelines to say how certain the evidence for a conclusion is: high, moderate, low or very low. It rates the evidence, not the diet, and it rates each outcome separately.

8. Review questions

1. Explain the 3 phases of a supervised very low calorie diet program to someone who has never heard of one, in plain words. Then say which phase the research suggests matters most for whether results last, and why.
2. NICE, the American Diabetes Association and the DiRECT investigators each describe the calorie level of these diets differently. Describe the difference, and explain why a coach should ask what a client's program provides rather than assume. This question draws on section 1.
3. DiRECT found remission in 46 percent of its program group at 12 months and in 10 percent of those with data at 5 years. Explain what changed in the trial after 2 years, and why the 5-year comparison is weaker evidence than the 12-month one. This question draws on section 4.
4. A client tells you she has bought a month of meal-replacement shakes online and plans to live on them to get off her diabetes tablets, which include a sulfonylurea. Write what you would say and what you would ask. Then say where the referral line is, and why her medicine matters for this particular diet. This question draws on sections 3 and 6.
5. Where did the belief that remission means diabetes is cured come from, and what does the consensus definition say? Write the 2 sentences you would use with a client who raises it.

9. References and Resources

American Diabetes Association Professional Practice Committee for Diabetes. (2026). 8. Obesity and weight management for the prevention and treatment of diabetes: Standards of Care in Diabetes-2026. Diabetes Care, 49(Suppl. 1), S166-S182. https://doi.org/10.2337/dc26-S008

Andela, S., Burrows, T. L., Baur, L. A., Coyle, D. H., Collins, C. E., & Gow, M. L. (2019). Efficacy of very low-energy diet programs for weight loss: A systematic review with meta-analysis of intervention studies in children and adolescents with obesity. Obesity Reviews, 20(6), 871-882. https://doi.org/10.1111/obr.12830

Ard, J. D., Lewis, K. H., Rothberg, A., Auriemma, A., Coburn, S. L., Cohen, S. S., Loper, J., Matarese, L., Pories, W. J., & Periman, S. (2019). Effectiveness of a total meal replacement program (OPTIFAST Program) on weight loss: Results from the OPTIWIN study. Obesity, 27(1), 22-29. https://doi.org/10.1002/oby.22303

Astbury, N. M., Aveyard, P., Nickless, A., Hood, K., Corfield, K., Lowe, R., & Jebb, S. A. (2018). Doctor Referral of Overweight People to Low Energy total diet replacement Treatment (DROPLET): Pragmatic randomised controlled trial. BMJ, 362, Article k3760. https://doi.org/10.1136/bmj.k3760

Astbury, N. M., Edwards, R. M., Ghebretinsea, F., Shanyinde, M., Mollison, J., Aveyard, P., & Jebb, S. A. (2021). Extended follow-up of a short total diet replacement programme: Results of the Doctor Referral of Overweight People to Low Energy total diet replacement Treatment (DROPLET) randomised controlled trial at 3 years. International Journal of Obesity, 45(11), 2432-2438. https://doi.org/10.1038/s41366-021-00915-1

Churuangsuk, C., Hall, J., Reynolds, A., Griffin, S. J., Combet, E., & Lean, M. E. J. (2022). Diets for weight management in adults with type 2 diabetes: An umbrella review of published meta-analyses and systematic review of trials of diets for diabetes remission. Diabetologia, 65(1), 14-36. https://doi.org/10.1007/s00125-021-05577-2

Frank, A., Graham, C., & Frank, S. (1981). Fatalities on the liquid-protein diet: An analysis of possible causes. International Journal of Obesity, 5(3), 243-248. pubmed.ncbi.nlm.nih.gov/7275462

Harris, R. A., Fernando, H. A., Seimon, R. V., da Luz, F. Q., Gibson, A. A., Touyz, S. W., & Sainsbury, A. (2022). Effects of total diet replacement programs on mental well-being: A systematic review with meta-analyses. Obesity Reviews, 23(11), Article e13465. https://doi.org/10.1111/obr.13465

Haywood, C. J., Prendergast, L. A., Purcell, K., Le Fevre, L., Lim, W. K., Galea, M., & Proietto, J. (2018). Very low calorie diets for weight loss in obese older adults: A randomized trial. The Journals of Gerontology: Series A, 73(1), 59-65. https://doi.org/10.1093/gerona/glx012

Hemmingsson, E., Johansson, K., Eriksson, J., Sundström, J., Neovius, M., & Marcus, C. (2012). Weight loss and dropout during a commercial weight-loss program including a very-low-calorie diet, a low-calorie diet, or restricted normal food: Observational cohort study. The American Journal of Clinical Nutrition, 96(5), 953-961. https://doi.org/10.3945/ajcn.112.038265

Hickson, K. A., Heppenstall, C., Treweeke, A., Coghill, E., Megson, I. L., Nicolson, S., Macfarlane, D. P., & MacRury, S. M. (2025). Efficacy of a homemade very low calorie diet to achieve prevention or remission of type 2 diabetes: A pilot study. Journal of Human Nutrition and Dietetics, 38(5), Article e70128. https://doi.org/10.1111/jhn.70128

Jebeile, H., Baur, L. A., Kwok, C., Alexander, S., Brown, J., Collins, C. E., Cowell, C. T., Day, K., Garnett, S. P., Gow, M. L., Grunseit, A. M., Henderson, M., House, E. T., Inkster, M. K., Lang, S., Paxton, S. J., Truby, H., Varady, K. A., & Lister, N. B. (2024). Symptoms of depression, eating disorders, and binge eating in adolescents with obesity: The Fast Track to Health randomized clinical trial. JAMA Pediatrics, 178(10), 996-1005. https://doi.org/10.1001/jamapediatrics.2024.2851

Johansson, K., Neovius, M., & Hemmingsson, E. (2014). Effects of anti-obesity drugs, diet, and exercise on weight-loss maintenance after a very-low-calorie diet or low-calorie diet: A systematic review and meta-analysis of randomized controlled trials. The American Journal of Clinical Nutrition, 99(1), 14-23. https://doi.org/10.3945/ajcn.113.070052

Johansson, K., Sundström, J., Marcus, C., Hemmingsson, E., & Neovius, M. (2014). Risk of symptomatic gallstones and cholecystectomy after a very-low-calorie diet or low-calorie diet in a commercial weight loss program: 1-year matched cohort study. International Journal of Obesity, 38(2), 279-284. https://doi.org/10.1038/ijo.2013.83

Lean, M. E. J., Leslie, W. S., Barnes, A. C., Brosnahan, N., Thom, G., McCombie, L., Peters, C., Zhyzhneuskaya, S., Al-Mrabeh, A., Hollingsworth, K. G., Rodrigues, A. M., Rehackova, L., Adamson, A. J., Sniehotta, F. F., Mathers, J. C., Ross, H. M., McIlvenna, Y., Stefanetti, R., Trenell, M., . . . Taylor, R. (2018). Primary care-led weight management for remission of type 2 diabetes (DiRECT): An open-label, cluster-randomised trial. The Lancet, 391(10120), 541-551. https://doi.org/10.1016/S0140-6736(17)33102-1

Lean, M. E. J., Leslie, W. S., Barnes, A. C., Brosnahan, N., Thom, G., McCombie, L., Peters, C., Zhyzhneuskaya, S., Al-Mrabeh, A., Hollingsworth, K. G., Rodrigues, A. M., Rehackova, L., Adamson, A. J., Sniehotta, F. F., Mathers, J. C., Ross, H. M., McIlvenna, Y., Welsh, P., Kean, S., . . . Taylor, R. (2019). Durability of a primary care-led weight-management intervention for remission of type 2 diabetes: 2-year results of the DiRECT open-label, cluster-randomised trial. The Lancet Diabetes & Endocrinology, 7(5), 344-355. https://doi.org/10.1016/S2213-8587(19)30068-3

Lean, M. E. J., Leslie, W. S., Barnes, A. C., Brosnahan, N., Thom, G., McCombie, L., Kelly, T., Irvine, K., Peters, C., Zhyzhneuskaya, S., Hollingsworth, K. G., Adamson, A. J., Sniehotta, F. F., Mathers, J. C., McIlvenna, Y., Welsh, P., McConnachie, A., McIntosh, A., Sattar, N., & Taylor, R. (2024). 5-year follow-up of the randomised Diabetes Remission Clinical Trial (DiRECT) of continued support for weight loss maintenance in the UK: An extension study. The Lancet Diabetes & Endocrinology, 12(4), 233-246. https://doi.org/10.1016/S2213-8587(23)00385-6

Leslie, W. S., Ali, E., Harris, L., Messow, C.-M., Brosnahan, N. T., Thom, G., McCombie, E. L., Barnes, A. C., Sattar, N., Taylor, R., & Lean, M. E. J. (2021). Antihypertensive medication needs and blood pressure control with weight loss in the Diabetes Remission Clinical Trial (DiRECT). Diabetologia, 64(9), 1927-1938. https://doi.org/10.1007/s00125-021-05471-x

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

Lim, E. L., Hollingsworth, K. G., Aribisala, B. S., Chen, M. J., Mathers, J. C., & Taylor, R. (2011). Reversal of type 2 diabetes: Normalisation of beta cell function in association with decreased pancreas and liver triacylglycerol. Diabetologia, 54(10), 2506-2514. https://doi.org/10.1007/s00125-011-2204-7

Marwood, J., Radley, D., Evans, T., Matu, J., Clare, K., Bakhai, C., & Ells, L. J. (2025). A cross-sectional analysis of emotional and binge eating in UK adults enrolled on the NHS low-calorie diet pilot for type 2 diabetes. Clinical Obesity, 15(5), Article e70025. https://doi.org/10.1111/cob.70025

McKechnie, T., Lee, Y., Dionne, J., Doumouras, A., Parpia, S., Bhandari, M., & Eskicioglu, C. (2023). Very low energy diets prior to bariatric surgery may reduce postoperative morbidity: A systematic review and meta-analysis of randomized controlled trials. Frontiers in Nutrition, 10, Article 1211575. https://doi.org/10.3389/fnut.2023.1211575

Muscogiuri, G., El Ghoch, M., Colao, A., Hassapidou, M., Yumuk, V., Busetto, L., & Obesity Management Task Force of the European Association for the Study of Obesity. (2021). European guidelines for obesity management in adults with a very low-calorie ketogenic diet: A systematic review and meta-analysis. Obesity Facts, 14(2), 222-245. https://doi.org/10.1159/000515381

National Institute for Health and Care Excellence. (2025). Overweight and obesity management (NICE Guideline NG246). nice.org.uk/guidance/ng246/chapter/​Physical-activity-and-diet

National Institute of Diabetes and Digestive and Kidney Diseases. (n.d.-a). Dieting & gallstones. National Institutes of Health. niddk.nih.gov/health-information/digestive-diseases/​gallstones/dieting

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

National Institute of Diabetes and Digestive and Kidney Diseases. (n.d.-c). Symptoms & causes of gallstones. National Institutes of Health. niddk.nih.gov/health-information/digestive-diseases/​gallstones/symptoms-causes

Parretti, H. M., Jebb, S. A., Johns, D. J., Lewis, A. L., Christian-Brown, A. M., & Aveyard, P. (2016). Clinical effectiveness of very-low-energy diets in the management of weight loss: A systematic review and meta-analysis of randomized controlled trials. Obesity Reviews, 17(3), 225-234. https://doi.org/10.1111/obr.12366

Price, S. A., & Sumithran, P. (2022). Using a very low energy diet to achieve substantial preconception weight loss in women with obesity: A review of the safety and efficacy. Nutrients, 14(20), Article 4423. https://doi.org/10.3390/nu14204423

Rehackova, L., Rodrigues, A. M., Thom, G., Brosnahan, N., Barnes, A. C., McCombie, L., Leslie, W. S., Zhyzhneuskaya, S., Peters, C., Adamson, A. J., Lean, M. E. J., Taylor, R., & Sniehotta, F. F. (2022). Participant experiences in the Diabetes REmission Clinical Trial (DiRECT). Diabetic Medicine, 39(1), Article e14689. https://doi.org/10.1111/dme.14689

Riddle, M. C., Cefalu, W. T., Evans, P. H., Gerstein, H. C., Nauck, M. A., Oh, W. K., Rothberg, A. E., le Roux, C. W., Rubino, F., Schauer, P., Taylor, R., & Twenefour, D. (2021). Consensus report: Definition and interpretation of remission in type 2 diabetes. Diabetes Care, 44(10), 2438-2444. https://doi.org/10.2337/dci21-0034

Sattar, N., Welsh, P., Leslie, W. S., Thom, G., McCombie, L., Brosnahan, N., Richardson, J., Gill, J. M. R., Crawford, L., & Lean, M. E. J. (2023). Dietary weight-management for type 2 diabetes remissions in South Asians: The South Asian diabetes remission randomised trial for proof-of-concept and feasibility (STANDby). The Lancet Regional Health: Southeast Asia, 9, Article 100111. https://doi.org/10.1016/j.lansea.2022.100111

Sours, H. E., Frattali, V. P., Brand, C. D., Feldman, R. A., Forbes, A. L., Swanson, R. C., & Paris, A. L. (1981). Sudden death associated with very low calorie weight reduction regimens. The American Journal of Clinical Nutrition, 34(4), 453-461. https://doi.org/10.1093/ajcn/34.4.453

Stokes, C. S., Gluud, L. L., Casper, M., & Lammert, F. (2014). Ursodeoxycholic acid and diets higher in fat prevent gallbladder stones during weight loss: A meta-analysis of randomized controlled trials. Clinical Gastroenterology and Hepatology, 12(7), 1090-1100.e2. https://doi.org/10.1016/j.cgh.2013.11.031

Taheri, S., Zaghloul, H., Chagoury, O., Elhadad, S., Ahmed, S. H., El Khatib, N., Amona, R. A., El Nahas, K., Suleiman, N., Alnaama, A., Al-Hamaq, A., Charlson, M., Wells, M. T., Al-Abdulla, S., & Abou-Samra, A. B. (2020). Effect of intensive lifestyle intervention on bodyweight and glycaemia in early type 2 diabetes (DIADEM-I): An open-label, parallel-group, randomised controlled trial. The Lancet Diabetes & Endocrinology, 8(6), 477-489. https://doi.org/10.1016/S2213-8587(20)30117-0

Taylor, R., Barnes, A. C., Hollingsworth, K. G., Irvine, K. M., Solovyova, A. S., Clark, L., Kelly, T., Martin-Ruiz, C., Romeres, D., Koulman, A., Meek, C. M., Jenkins, B., Cobelli, C., & Holman, R. R. (2023). Aetiology of type 2 diabetes in people with a 'normal' body mass index: Testing the personal fat threshold hypothesis. Clinical Science, 137(16), 1333-1346. https://doi.org/10.1042/CS20230586

Tsai, A. G., & Wadden, T. A. (2006). The evolution of very-low-calorie diets: An update and meta-analysis. Obesity, 14(8), 1283-1293. https://doi.org/10.1038/oby.2006.146

Tsompanaki, E., Aveyard, P., Park, R. J., Jebb, S. A., & Koutoukidis, D. A. (2025). An intensive weight loss programme with behavioural support for people with type 2 diabetes at risk of eating disorders in England (ARIADNE): A randomised, controlled, non-inferiority trial. The Lancet Psychiatry, 12(7), 483-492. https://doi.org/10.1016/S2215-0366(25)00126-9

University of Oxford. (2025, July 8). The impact of low-energy total diet replacement with behavioural support for remission of type 2 diabetes on disordered eating: The ARIADNE randomised non-inferiority controlled trial (ClinicalTrials.gov Identifier NCT05744232). U.S. National Library of Medicine. https://clinicaltrials.gov/study/NCT05744232

Valabhji, J., Gorton, T., Barron, E., Safazadeh, S., Earnshaw, F., Helm, C., Virr, M., Kernan, J., Crowe, S., Aveyard, P., Wilding, J., Willis, T., Ells, L., O'Neill, S., Robertson, E., Jebb, S., Taylor, R., & Bakhai, C. (2024). Early findings from the NHS Type 2 Diabetes Path to Remission Programme: A prospective evaluation of real-world implementation. The Lancet Diabetes & Endocrinology, 12(9), 653-663. https://doi.org/10.1016/S2213-8587(24)00194-3

Xin, Y., Davies, A., McCombie, L., Briggs, A., Messow, C.-M., Grieve, E., Leslie, W. S., Taylor, R., & Lean, M. E. J. (2019). Within-trial cost and 1-year cost-effectiveness of the DiRECT/Counterweight-Plus weight-management programme to achieve remission of type 2 diabetes. The Lancet Diabetes & Endocrinology, 7(3), 169-172. https://doi.org/10.1016/S2213-8587(18)30346-2

Zhao, Y., Li, A., Yang, H., Xiao, M., Song, M., Shao, Z., Jiao, R., Pang, Y., Gao, W., Huang, T., Lv, J., Li, L., Yu, C., & Sun, D. (2024). The frequency of meal-replacement products drinking and all-cause, CVD, and cancer mortality. Nutrients, 16(21), Article 3770. https://doi.org/10.3390/nu16213770

Evidence rating and review record

The rated outcomes on this page use GRADE, a 4-level scale used in clinical guidelines. Each row identifies the method, source, outcome and comparison being rated, and ratings from different tools are not interchangeable. 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 low for another. Each row below says whether the rating comes from a named published review or is this page's own judgment, and exactly which comparison it rates. Two ratings on this page come from a published review; the other 5 are this page's own judgment, assigned from the evidence with each GRADE domain recorded in the working files, and 2 outcomes are not rated.

The rating in the banner is for type 2 diabetes remission at 12 months, because that is the outcome these programs were tested for and where the evidence is strongest. A high rating means the research is solid for that outcome, in those people, at that time; it does not mean the diet is right for everyone, and it does not mean a coach should recommend it.

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
Type 2 diabetes remission at 12 months, the main outcome and the rating in the banner	High	Churuangsuk et al., 2022, using GRADE. Formula total diet replacement programs with food reintroduction and support, compared with usual care, in adults with type 2 diabetes of short duration, in 2 randomized trials of 445 people (DiRECT and DIADEM-I)	Randomized trials start at high certainty. The reviewers judged both trials at low risk of bias, with outcomes specified in advance and adequate sample sizes, and did not lower the rating. The review describes both trials as having remission as the primary outcome, which DIADEM-I's own report does not support (see section 4), and one of the review's authors was a principal investigator of DiRECT. Both trials were open label. The rating applies to remission at 12 months only
Type 2 diabetes remission at 2 years	Moderate	This page's own judgment. The DiRECT program compared with best-practice diabetes care, in 298 adults aged 20 to 65 diagnosed within 6 years, body mass index 27 to 45, not on insulin, at 2 years	Starts high as a randomized trial. Risk of bias not lowered: open label, but remission is measured by a laboratory test and medicine records, and a sensitivity analysis was reported. Missing participants were counted as not in remission; this assumption does not by itself rule out missing-data bias. Inconsistency not assessable with a single trial. Indirectness not lowered for the population the trial enrolled. Lowered 1 level for imprecision about the size of the remission effect, not its direction: a single trial with 58 people in remission in total and a wide interval, odds ratio 25.8, from 8.3 to 80.8, every value of which favors the program. Publication bias not suspected
Type 2 diabetes remission at 5 years	Low	This page's own judgment. The original DiRECT program and comparison groups at 5 years, among people with data (118 and 93)	Starts high as a randomized comparison. Lowered one level for risk of bias: after 2 years the comparison group was told the results and encouraged to lose weight, so it no longer received usual care, and remission data were missing for 21 percent of the program group and 38 percent of the comparison group. Lowered one level for imprecision: 17 people in remission in total, odds ratio 2.0, from 0.6 to 7.5, an interval that includes no difference and a large benefit. Indirectness and publication bias not lowered. Low certainty here means the trial cannot say whether the program still made a difference at 5 years; it is not evidence that it made none
Body weight at 12 months, as measured	Moderate	This page's own judgment. Formula programs of about 800 calories a day with support, compared with usual care or nurse-led weight support, in adults with type 2 diabetes (DiRECT and DIADEM-I, both read in full) and adults with obesity (DROPLET), at 12 months	Starts high. Lowered one level for risk of bias: all 3 trials were open label, and more people left the formula groups than the comparison groups in DiRECT, so results depend on how missing weights were handled; the trials' sensitivity analyses gave similar answers, which is why it is not lowered further. Consistent in direction and similar in size, 6.1 to 8.8 kilograms. Not lowered for imprecision or indirectness. Weight is reported here as a measurement, not as a goal; see the standing rule below
Body weight at 3 to 5 years, as measured	Low	This page's own judgment. DROPLET at 3 years and the original DiRECT groups at 5 years	Starts high. Lowered one level for risk of bias: about a third of DROPLET's participants and nearly half of DiRECT's comparison group had no weight at follow-up, and DiRECT's comparison group was no longer receiving usual care after 2 years. Lowered 1 level for imprecision about the size and persistence of the long-term difference: the 5-year confidence interval includes no difference. The 3-year and 5-year estimates, 3.3 and 1.1 kilograms, describe different follow-up times and their confidence intervals overlap; their numerical difference alone does not demonstrate inconsistency. Indirectness and publication bias not lowered
Body weight at 3 months, as measured, very low energy diets compared with low energy diets	Low	Churuangsuk et al., 2022, using GRADE (electronic supplementary material, Table 4). Very low energy diets of 400 to 500 calories a day for 8 to 12 weeks, compared with low energy diets of 1,000 to 1,500 calories a day, in adults with type 2 diabetes, in 2 randomized trials of 100 people, analyzed among those who completed them, at 3 months	Randomized trials start at high certainty. The reviewers lowered the rating 1 level for risk of bias and 1 level for imprecision, citing trials at high risk of bias and a small total sample; they did not lower it for inconsistency or indirectness, and publication bias was not detected. The pooled difference was 6.6 kilograms more weight lost, from 3.7 to 9.5. This rating applies to this separate comparison only and is not carried to the 12-month weight row above. Weight is reported here as a measurement, not as a goal
Gallstones needing hospital care, a harm	Low	This page's own judgment. A 500-calorie formula diet compared with a 1,200 to 1,500 calorie diet in a Swedish commercial program, in 6,640 matched adults over 1 year (Johansson, Sundström, et al., 2014)	Observational evidence starts low. Not raised for the size of the association, a hazard ratio of 3.4, because people chose their own diet and part of the difference reflected faster weight loss; 62 events in total. Not lowered further. Trials report gallstone events too, but in numbers too small to estimate a rate. Low certainty here concerns how much the risk rises, not whether gallstones are a recognized harm of rapid weight loss
Eating disorder symptoms and mental well-being	Not rated	Not rated by this page. The evidence is one randomized trial of 56 adults, read in its corrected full report, uncontrolled before-and-after studies pooled in a review, and one trial in adolescents in which every participant received the very low energy phase	The evidence available does not support a trustworthy rating. Average symptom scores did not worsen in the supervised studies, but some adolescents needed additional support or referral. Group averages do not show that every participant was unaffected, and these studies do not establish safety for unsupervised use or for people they excluded
Heart attacks, strokes and death	Not rated	Not rated by this page. No randomized trial found was designed or large enough to estimate a reliable effect on these outcomes	DiRECT recorded fewer serious adverse events in its program group over 5 years, but it was not powered for these outcomes, and a difference in serious adverse events is not evidence that the diet prevents disease

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.

Status: reviewed and approved by James Peth, MS, MPH, PhD, on October 4, 2026, after a combined final review of the second batch of 5 archive pages, the repairs it asked for, a targeted recheck, and a check of the corrected ARIADNE trial report, its appendix and its correction. What changed: first version, October 3, 2026. Repaired October 4, 2026, after the combined final review: medication withdrawal described as a planned protocol with exceptions; the insulin exclusion limited to DiRECT; adolescent support and referral findings added; the cancer statement bounded; rating reasons revised; a second published rating added; related-page links updated. Prepared by James Peth, MS, MPH, PhD.

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 American Diabetes Association's Standards of Care, updated every year, and the NICE guideline on this page are in that category 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.