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Research · Diets

Very low calorie diet

In trials, total diet replacement at about 800 to 850 kcal a day put 46% to 61% of people with early type 2 diabetes into remission at one year and added about 4 to 7 kg of weight loss. Both effects shrank over 2 to 5 years. Gallstone risk was about 3 times that of a low-calorie diet.

Add to Bio HackChecked 2026-11-13
Status
A dietary pattern, not a regulated product. Many programs supply commercial formula products.
Also called
very low calorie diet, very-low-calorie diet, VLCD, very low energy diet, VLED, low energy diet, total diet replacement, TDR, formula diet, meal replacement, meal replacement shakes, soup and shake diet, DiRECT diet, Counterweight-Plus
Followed for
weight loss, type 2 diabetes remission, blood sugar, quality of life

Strong several reviews agree · Moderate one review or consistent trials · Limited one or a few small studies · Untested no study in people, listed with what it rests on

Shown to help4

Reported risks2

What people follow it for, and what was found

Shown to help4

Moderate

Type 2 diabetes remission

Shown to put 46% to 61% of people with early type 2 diabetes into remission at 12 months, against 4% to 12% with usual care, in two trials.

Compared with care by guidelines, at UK general practices [1], [2]; the original control group and a non-extension group whose intervention was withdrawn [3]; usual diabetes care based on clinical guidelines, in Qatar [4]; standard care, in the two trials of total diet replacement [5]

The numbers and sources
Effect
In DiRECT, 68 of 149 (46%) reached remission at 12 months against 6 (4%) of controls (OR 19.7, 95% CI 7.8 to 49.8). Remission rose with weight loss, reaching 86% of those who lost 15 kg or more [1]. At 24 months, 36% were in remission against 3% (aOR 25.82) [2]. At 5 years, 13% of extension participants were in remission, and 26% of those in remission at 2 years remained so [3]. In DIADEM-I, remission at 12 months was 61% against 12% (OR 12.03, 95% CI 5.17 to 28.03) [4]. A systematic review found remission at one year in a median 54% of participants in trials that began with low-energy total diet replacement (GRADE high). In other trials, it was 11% with meal replacements and 15% with Mediterranean diets (GRADE moderate to low). These are separate trials, not one comparison [5].
Population
306 adults aged 20 to 65 with type 2 diabetes for under 6 years, BMI 27 to 45 and not on insulin, at 49 UK practices [1][2][3]; 158 adults aged 18 to 50 from the Middle East and north Africa with diabetes for 3 years or less, in Qatar [4]; 16 studies of remission [5].
Sources
[1], [2], [3], [4], [5]
Caveats
Both trials were open-label and withdrew diabetes drugs at the start [1][4]. Most evidence covers one year or less [5]. Remission fell from 46% at one year to 36% at two [1][2].
Moderate

Weight loss with total diet replacement

Shown to add about 4 to 7 kg of weight loss at one year against behavioral programs or usual care, narrowing to about 1.3 kg by 3 to 5 years.

Compared with care by guidelines, at UK general practices [1]; usual diabetes care based on clinical guidelines, in Qatar [4]; low-energy diets of 1,000 to 1,500 kcal a day [5]; a behavioural programme alone [6]; usual care of nurse-led weight-loss support and a diet with modest energy restriction, in Oxfordshire, UK [7]

The numbers and sources
Effect
Against a behavioral program alone, very low energy diets with a behavioral program lost 3.9 kg more at 1 year (95% CI -6.7 to -1.1), 1.4 kg more at 24 months (95% CI -2.6 to -0.2) and 1.3 kg more at 38 to 60 months (95% CI -2.9 to 0.2) [6]. In type 2 diabetes, 400 to 500 kcal diets for 8 to 12 weeks lost 6.6 kg more than 1,000 to 1,500 kcal diets (GRADE low) [5]. In DROPLET, the program lost 10.7 kg against 3.1 kg with nurse-led usual care at 12 months (difference -7.2 kg, 95% CI -9.4 to -4.9), and 45% against 15% lost at least 10% of body weight [7]. In DiRECT, the adjusted difference was -8.8 kg (95% CI -10.3 to -7.3) at 12 months [1], and in DIADEM-I it was -6.08 kg (95% CI -8.37 to -3.79) [4].
Population
Adults with overweight in randomized trials [6]; adults with type 2 diabetes [5]; 278 adults with obesity at 10 UK practices, 73% measured at 12 months [7]; 306 [1] and 158 [4] adults with type 2 diabetes.
Sources
[1], [4], [5], [6], [7]
Caveats
The difference at 38 to 60 months was not significant [6].
Moderate

Weight loss with partial meal replacements

Shown to add 1.4 to 6.1 kg of weight loss at one year against diets without meal replacements, with larger gaps when more support was given.

Compared with low-energy weight-loss diets with the same energy [5]; weight-loss interventions without meal replacements, with or without support [8]

The numbers and sources
Effect
Diets with meal replacements lost 1.44 kg more than other diets (95% CI -2.48 to -0.39). With support, the gap was 2.22 kg against other diets with support and 3.87 kg against diets without support. With enhanced support, it was 6.13 kg (95% CI -7.35 to -4.91) [8]. In type 2 diabetes, formula meal replacements lost 2.4 kg more over 12 to 52 weeks (GRADE moderate) [5].
Population
23 trials with 7,884 adults with overweight or obesity, excluding diets under 800 kcal and total diet replacement [8]; adults with type 2 diabetes [5].
Sources
[5], [8]
Caveats
Heterogeneity reached 81% in one comparison [8]. Five of 23 studies had a high risk of bias in at least one domain [8].
Limited

Quality of life

One trial found quality of life scores rose 6.4 points more than with usual care at 12 months in type 2 diabetes.

Compared with care by guidelines, at UK general practices [1]

The numbers and sources
Effect
EuroQol visual analogue scores rose 7.2 points on the program and fell 2.9 points in controls (adjusted difference 6.4, 95% CI 2.5 to 10.3) [1].
Population
298 adults with type 2 diabetes [1].
Sources
[1]
Caveats
Open-label, so participants knew their group [1].

How trials defined it

DiRECT used an 825 to 853 kcal a day formula diet for 12 to 20 weeks, then stepped food reintroduction over 2 to 8 weeks and structured support to keep weight off, with diabetes and blood pressure drugs withdrawn at the start [1]. DROPLET used formula products providing 810 kcal a day as the only food for 8 weeks, then food reintroduction, with weekly then monthly support [7]. DIADEM-I used formula low-energy meal replacements, then gradual food reintroduction and physical activity support [4]. Very low energy diets in diabetes reviews provided 1.7 to 2.1 MJ (400 to 500 kcal) a day for 8 to 12 weeks [5]. A Swedish commercial program used 500 kcal a day for 3 months, defining a very low calorie diet as under 800 kcal a day [9], and a US program used a 520 kcal a day liquid protein diet for 16 weeks [10]. One trial compared 600 and 700 kcal a day diets with 52 or 77 g of protein for 8 weeks, testing a European Food Safety Authority recommendation to raise protein in total diet replacement from 50 to 75 g a day [11]. Partial meal replacement trials replaced some meals and kept intake above 800 kcal a day [8].

Risks

Reported risks2

Limited

Gallstones

Linked to about 3 times the risk of gallstones needing hospital care against a low-calorie diet in a large Swedish cohort, though the absolute risk was low.

The numbers and sources
Effect
Gallstones needing hospital care occurred at 152 against 44 per 10,000 person-years on a 500 kcal diet and a 1,200 to 1,500 kcal diet (HR 3.4, 95% CI 1.8 to 6.3), one extra case for every 92 people. Cholecystectomy HR was 3.2 [9]. On a 520 kcal liquid diet for 16 weeks, gallstones appeared on ultrasound in 28% of people taking placebo, against 2% to 8% on ursodeoxycholic acid [10]. In DiRECT, biliary colic and abdominal pain in one participant were judged potentially related to the diet [1]. A meta-analysis recorded one hospital admission for cholecystitis on very low energy diets and none in comparison groups [6].
Population
3,320 matched pairs in a Swedish commercial program [9]; 1,004 adults with BMI 38 or more in a US program [10]; trial participants [1][6].
Sources
[1], [6], [9], [10]
Caveats
The Swedish data are an observational matched cohort, and the hazard ratio fell to 2.5 after adjusting for 3-month weight loss [9]. The 28% figure counts gallstones seen on ultrasound, not all causing symptoms [10].
Limited

Lean mass loss

One trial found lean mass fell 6% in 8 weeks, 27% of the weight lost, whatever the protein intake. Pooled trials found exercise kept 0.83 kg more.

The numbers and sources
Effect
On 600 or 700 kcal a day for 8 weeks, lean mass fell 6% and resting metabolic rate 9% to 10% from baseline, and lean mass made up 27% of weight lost in both protein groups [11]. Adding exercise retained 0.83 kg more fat-free mass than the diet alone (95% CI 0.17 to 1.49) [12].
Population
108 adults with BMI 28 to 40 [11]; 5 trials with 241 adults with overweight or obesity [12].
Sources
[11], [12]
Caveats
Few trials with risk of bias concerns in the exercise analysis [12].

Checked, no increase found1

Moderate

Adverse events in trials

In primary care trials, adverse events of moderate or greater severity were about as common as with usual care, and dropout matched behavioral programs.

The numbers and sources
Effect
Moderate or worse adverse events affected 11% on total diet replacement and 12% on usual care [7]. In DiRECT, 7 of 157 intervention participants (4%) and 2 controls (1%) had serious adverse events in year one, 2 of them potentially diet-related [1]. In year two, serious adverse events were fewer in the intervention group, 9 against 22 [2], and over 5 years they ran at 4.8 against 10.2 per 100 patient-years [3]. In DIADEM-I, the five serious adverse events were all in the control group [4]. Across trials, 19% stopped very low energy diets early against 20% of comparison groups (RR 0.96, 95% CI 0.56 to 1.66) [6].
Population
278 adults [7]; 306 [1][2][3] and 158 [4] adults with type 2 diabetes; adults in randomized trials [6].
Sources
[1], [2], [3], [4], [6], [7]
Caveats
Most trials supervised participants in primary care and reduced medication by protocol [1][4].

Sources

  1. Lean ME, Leslie WS, Barnes AC, et al. Primary care-led weight management for remission of type 2 diabetes (DiRECT): an open-label, cluster-randomised trial. The Lancet. 2018. https://doi.org/10.1016/s0140-6736(17)33102-1
  2. Lean MEJ, Leslie WS, Barnes AC, et al. 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. 2019. https://doi.org/10.1016/s2213-8587(19)30068-3
  3. Lean ME, Leslie WS, Barnes AC, et al. 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. 2024. https://doi.org/10.1016/s2213-8587(23)00385-6
  4. Taheri S, Zaghloul H, Chagoury O, et al. 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. 2020. https://doi.org/10.1016/s2213-8587(20)30117-0
  5. Churuangsuk C, Hall J, Reynolds A, et al. 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. 2022. https://doi.org/10.1007/s00125-021-05577-2
  6. Parretti HM, Jebb SA, Johns DJ, et al. 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. 2016. https://doi.org/10.1111/obr.12366
  7. Astbury NM, Aveyard P, Nickless A, et al. Doctor Referral of Overweight People to Low Energy total diet replacement Treatment (DROPLET): pragmatic randomised controlled trial. BMJ. 2018. https://doi.org/10.1136/bmj.k3760
  8. Astbury NM, Piernas C, Hartmann-Boyce J, et al. A systematic review and meta-analysis of the effectiveness of meal replacements for weight loss. Obesity Reviews. 2019. https://doi.org/10.1111/obr.12816
  9. Johansson K, Sundström J, Marcus C, et al. 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. 2014. https://doi.org/10.1038/ijo.2013.83
  10. Shiffman ML, Kaplan GD, Brinkman-Kaplan V, et al. Prophylaxis against gallstone formation with ursodeoxycholic acid in patients participating in a very-low-calorie diet program. Annals of Internal Medicine. 1995. https://doi.org/10.7326/0003-4819-122-12-199506150-00002
  11. Magkos F, Hjorth MF, Asping S, et al. A protein-supplemented very-low-calorie diet does not mitigate reductions in lean mass and resting metabolic rate in subjects with overweight or obesity: A randomized controlled trial. Clinical Nutrition. 2021. https://doi.org/10.1016/j.clnu.2021.10.006
  12. Lowrie FJ, Rahimi MM, Hogan CM, et al. The impact of exercise on fat free mass reduction during very low energy diet-induced weight loss in adults with overweight or obesity: A systematic review and meta-analysis. Obesity Research & Clinical Practice. 2025. https://doi.org/10.1016/j.orcp.2025.10.001

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