Does a vegetarian diet help with weight loss?

Modestly, over months, and less as time goes on. A meta-analysis of 12 randomized trials in 1,151 people found those put on vegetarian diets lost about 4.4 lb (2 kg) more than those on non-vegetarian diets over a median 18 weeks (95% CI 2.7 to 6.2 lb (1.23 to 2.80 kg)). In trials that followed people for a year or more, the gap shrank to 2.5 lb (1.13 kg). The newest review, from 2026, found little to no difference in body weight against omnivorous diets.

Unsettled. The reviews disagree on size. Most pooled estimates sit between 4.4 and 8.8 lb (2 and 4 kg) over a few months, and the 2026 review comparing plant-based with omnivorous diets in 10 trials found little to no difference. The gap depends on what the vegetarian diet was compared with and how long people were followed, and long trials are few.

What the trials found

Vegetarian against other diets

In the 12-trial review, vegan diets accounted for most of the effect, about 5.6 lb (95% CI 4.4 to 6.7; metric: 2.52 kg, 1.98 to 3.02). Lacto-ovo-vegetarian diets, which keep dairy and eggs, gave 3.3 lb (1.48 kg), with an interval from -3.43 to 0.47 that does not rule out no effect. Those are subgroup results within one review.

An umbrella review graded the vegan result in the general healthy population as moderate certainty: 5.6 lb (2.52 kg) less body weight across 8 randomized trials (95% CI 1.98 to 3.06).

In people with overweight or a health condition

A meta-analysis of 9 trials in 1,628 people with overweight or obesity found vegetarian diets lowered weight by 7.9 lb (95% CI 5.4 to 10; metric: 3.60 kg, 2.46 to 4.75). Body mass index and waist size did not fall significantly in the same analysis, and the reviewers rated the quality of evidence very low for most outcomes. Across 11 trials in 796 people with overweight or type 2 diabetes, vegan diets of at least 12 weeks lowered weight by 9 lb (95% CI 5.3 to 13; metric: 4.1 kg, 2.4 to 5.9). The authors note that part of that may come from differences in calories and macronutrients between the diets.

In 20 trials of 1,878 people with or at high risk of heart disease, about six months on a vegetarian diet went with 7.5 lb (3.4 kg) less body weight (95% CI 2.0 to 4.9). Weight was a secondary outcome there. A 2015 review of 15 trials of vegetarian diets without calorie limits found 7.5 lb (3.4 kg) of weight change by intention to treat and 10 lb (4.6 kg) among people who completed. Only 4 of those studies had a control group with no intervention, and the authors describe the quality as variable.

The newest review

A 2026 meta-analysis of 10 randomized trials in people with overweight or obesity compared plant-based with omnivorous diets and found little to no difference in body weight or body fat mass. BMI may fall, on very low certainty evidence. Several earlier reviews compared vegetarian diets with any control or non-vegetarian diet, and this one compared them only with omnivorous eating.

Single trials

In a randomized crossover trial of 62 adults with overweight, 16 weeks of a low-fat vegan diet gave a net change of 13 lb (95% CI 9.9 to 17; metric: 6.0 kg, 4.5 to 7.5) while a Mediterranean diet gave 0 lb (0.0 kg). Both diets were eaten without calorie limits, and the trial comes from one research group, the Physicians Committee. In 22 pairs of identical twins, the twin on a healthy vegan diet lost 4.2 lb (1.9 kg) more over 8 weeks (95% CI 0.6 to 3.3) than the twin on a healthy omnivorous diet. Weight was a secondary outcome, and the vegan twins ate fewer calories.

Over years, in ordinary life

In EPIC-Oxford, 21,966 UK adults gained about 389 to 398 g a year over a median 5.3 years. Vegans gained somewhat less, 284 g a year in men and 303 g in women. Weight was self-reported, and this is an observational cohort that cannot show the diet caused the difference.

Who should be careful

Cutting out meat, or all animal foods, to lose weight changes more than weight.

Not for everyone. Vegans and vegetarians have a higher risk of vitamin B12 deficiency, because natural sources are limited to animal foods, according to NIH ODS. Fortified foods or supplements substantially reduce that risk. In 1,994 Seventh-day Adventists, who use fortified foods and supplements more often than other vegetarians, serum B12 did not differ from omnivores (MD -9.85 pmol/L, 95% CI -45.64 to 25.94).

In EPIC-Oxford, followed for 17.6 years, vegans had 2.31 times the hip fracture risk of meat eaters (95% CI 1.66 to 3.22) after adjustment for lifestyle and body mass index. In absolute terms that is 14.9 more cases for every 1,000 people over 10 years. Vegetarians had a smaller raised risk (HR 1.25, 1.04 to 1.50). These are observational data.

Children are a separate case. A 2026 meta-analysis of 59 studies in 48,626 children found vegetarian children leaner and shorter on average, with higher odds of iron deficiency and anemia in lacto-ovo-vegetarians and of B12 deficiency in vegans. Group averages for most nutrients stayed within pediatric reference ranges. None of this is evidence for using the diet to slim a child.

Across 26 cross-sectional studies of 23,783 adults, vegetarians and vegans scored higher on symptoms of orthorexia, an unhealthy fixation on eating correctly, than omnivores (Cohen's d 0.46, 95% CI 0.33 to 0.60). The studies were all cross-sectional and of low quality, so they show a pattern without cause. For anyone with a history of disordered eating, a restrictive diet for weight loss is worth discussing with the person treating you.

What expert bodies say

The NIH Office of Dietary Supplements states the B12 risk for vegans and vegetarians and says fortified foods or supplements reduce it. We did not find an expert body position on vegetarian diets for weight loss in our sources. The 2016 position of the Academy of Nutrition and Dietetics on vegetarian diets was not in our corpus, so we do not cite it.

How we searched

What would change this answer

• Results from the six ongoing studies listed in the 2026 review, which could settle whether the gap against omnivorous diets is real.
• More trials that follow people for a year or longer. The effect shrinks with time, and few trials run that long.
• Trials that match calories between diets, to show whether the diet does anything beyond helping people eat less.

More on vegetarian eating beyond weight: Vegetarian.

Sources

1. ev-vegwl-01 · Meta-analysis or systematic review · meta-analysis of randomized controlled trials · n = 1151
   Overall, individuals assigned to the vegetarian diet groups lost significantly more weight than those assigned to the non-vegetarian diet groups (weighted mean difference, -2.02 kg; 95 % confidence interval [CI]: -2.80 to -1.23).
   
   Who: participants of 12 RCTs of vegetarian versus non-vegetarian diets, median intervention 18 weeks
   Effect: weight WMD -4.5 lb (95% CI -6.2 to -2.7; metric: -2.02 kg, -2.80 to -1.23)
   Certainty: The main answer: there is an effect, but it is moderate.
   J Gen Intern Med, 2016 · checked 2026-10-07 · we read the abstract
2. ev-vegwl-02 · Meta-analysis or systematic review · meta-analysis of randomized controlled trials, subgroup analysis · n = 12 trials
   Subgroup analysis detected significant weight reduction in subjects consuming a vegan diet (-2.52 kg; 95 % CI: -3.02 to -1.98) and, to a lesser extent, in those given lacto-ovo-vegetarian diets (-1.48 kg; 95 % CI: -3.43 to 0.47).
   
   Who: RCT subgroups by type of vegetarian diet
   Effect: vegan -5.6 lb (95% CI -6.7 to -4.4; metric: -2.52 kg, -3.02 to -1.98); lacto-ovo-vegetarian -3.3 lb (-7.6 to 1; metric: -1.48 kg, -3.43 to 0.47)
   Certainty: The difference between vegan and lacto-ovo diet is at the subgroup level.
   J Gen Intern Med, 2016 · checked 2026-10-07 · we read the abstract
3. ev-vegwl-03 · Meta-analysis or systematic review · meta-analysis of randomized controlled trials, subgroup analysis · n = 12 trials
   The weight loss for subjects with follow-up of <1 year was greater (-2.05 kg; 95 % CI: -2.85 to -1.25) than those with follow-up of ≥1 year (-1.13 kg; 95 % CI: -2.04 to -0.21).
   
   Who: RCT subgroups by follow-up period
   Effect: follow-up under 1 year -4.5 lb (95% CI -6.3 to -2.8; metric: -2.05 kg, -2.85 to -1.25); 1 year or more -2.5 lb (-4.5 to -0.46; metric: -1.13 kg, -2.04 to -0.21)
   Certainty: Few long-term RCTs.
   J Gen Intern Med, 2016 · checked 2026-10-07 · we read the abstract
4. ev-vegwl-04 · Randomized controlled trial(s) · systematic review and meta-analysis of intervention trials · n = 15 trials
   Prescription of vegetarian diets was associated with a mean weight change of -3.4 kg (95% CI -4.4 to -2.4; P<0.001) in an intention-to-treat analysis and -4.6 kg (95% CI -5.4 to -3.8; P<0.001) in a completer analysis (omitting missing post-intervention values).
   
   Who: adults in intervention trials of vegetarian diets of at least 4 weeks without energy intake limitations
   Effect: mean weight change -7.5 lb (95% CI -9.7 to -5.3; metric: -3.4 kg, -4.4 to -2.4) intention-to-treat; -10 lb (-12 to -8.4; metric: -4.6 kg, -5.4 to -3.8) completers
   Certainty: Only 4 studies had an untreated control; the authors write of variable quality.
   J Acad Nutr Diet, 2015 · checked 2026-10-07 · we read the abstract
5. ev-vegwl-05 · Meta-analysis or systematic review · systematic review and meta-analysis of RCTs with GRADE · n = 1628
   VDs decreased weight (MD -3.60 kg, 95%CI -4.75 to -2.46) and glucose (MD -10.64 mg/dL, 95%CI -15.77 to -5.51), but did not decrease WC (MD -3.00 cm, 95%CI -6.20 to 0.20), BMI (MD -0.87 kg/m2, 95%CI -1.80 to 0.06), or HC (MD: -0.86 cm, 95%CI -3.46 to 1.74).
   
   Who: people with overweight and obesity in RCTs of vegetarian versus omnivore diets
   Effect: weight MD -7.9 lb (95% CI -10 to -5.4; metric: -3.60 kg, -4.75 to -2.46); BMI and waist not significantly reduced; quality of evidence very low for most outcomes
   Certainty: Weight falls, but BMI and waist do not, GRADE very low.
   Int J Obes (Lond), 2023 · checked 2026-10-07 · we read the abstract
6. ev-vegwl-06 · Meta-analysis or systematic review · systematic review and meta-analysis of RCTs · n = 796
   In comparison with control diets, vegan diets reduced body weight (-4.1 kg, 95% confidence interval (CI) -5.9 to -2.4, p < 0.001), body mass index (BMI) (-1.38 kg/m2 , 95% CI -1.96 to -0.80, p < 0.001)
   
   Who: people with overweight or type 2 diabetes on vegan diets for at least 12 weeks versus control diets
   Effect: body weight -9 lb (95% CI -13 to -5.3; metric: -4.1 kg, -5.9 to -2.4); BMI -1.38 kg/m2 (-1.96 to -0.80)
   Certainty: Authors: part of the effect may come from differences in calories and macronutrients.
   Obes Rev, 2022 · checked 2026-10-07 · we read the abstract
7. ev-vegwl-07 · Meta-analysis or systematic review · systematic review and meta-analysis of RCTs with GRADE · n = 10 trials
   The available evidence suggests little to no difference between plant-based and omnivorous diets for body weight, systolic blood pressure, diastolic blood pressure, serum glucose, serum insulin, insulin sensitivity, total cholesterol, triglyceride, HDL cholesterol and body fat mass.
   
   Who: overweight or obese individuals in RCTs of plant-based versus omnivorous diets
   Effect: little to no difference for body weight and body fat mass; BMI may fall, very low certainty
   Certainty: The newest synthesis with GRADE diverges from earlier ones: comparison against omnivorous, not against any control.
   Nutrients, 2026 · checked 2026-10-07 · we read the abstract
8. ev-vegwl-08 · Meta-analysis or systematic review · systematic review and meta-analysis of RCTs · n = 1878
   Overall, relative to all comparison diets, meta-analyses showed that consuming vegetarian diets for an average of 6 months was associated with decreased LDL-C, HbA1c, and body weight by 6.6 mg/dL (95% CI, -10.1 to -3.1), 0.24% (95% CI, -0.40 to -0.07), and 3.4 kg (95% CI, -4.9 to -2.0), respectively
   
   Who: adults with or at high risk of cardiovascular disease, mean intervention 25.4 weeks
   Effect: body weight -7.5 lb (95% CI -11 to -4.4; metric: -3.4 kg, -4.9 to -2.0)
   Certainty: Weight is a secondary outcome; GRADE moderate only for LDL and HbA1c.
   JAMA Netw Open, 2023 · checked 2026-10-07 · we read the abstract
9. ev-vegwl-09 · Randomized controlled trial(s) · randomized crossover trial · n = 62
   Overall net weight changes were 0.0 (Mediterranean) and -6.0 kg (vegan), (treatment effect -6.0 kg [95% CI -7.5 to -4.5]; p < 0.001).
   
   Who: overweight adults, 16 weeks on each diet with a 4-week washout
   Effect: net weight change 0 lb (0.0 kg) Mediterranean vs -13 lb (-6.0 kg) vegan; treatment effect -13 lb (95% CI -17 to -9.9; metric: -6.0 kg, -7.5 to -4.5)
   Certainty: One research group (Physicians Committee); ad libitum diets.
   J Am Nutr Assoc, 2022 · checked 2026-10-07 · we read the abstract
10. ev-vegwl-10 · Randomized controlled trial(s) · single-center open-label parallel randomized clinical trial · n = 44
    After 8 weeks, compared with twins randomized to an omnivorous diet, the twins randomized to the vegan diet experienced significant mean (SD) decreases in low-density lipoprotein cholesterol concentration (-13.9 [5.8] mg/dL; 95% CI, -25.3 to -2.4 mg/dL), fasting insulin level (-2.9 [1.3] μIU/mL; 95% CI, -5.3 to -0.4 μIU/mL), and body weight (-1.9 [0.7] kg; 95% CI, -3.3 to -0.6 kg).
    
    Who: 22 pairs of identical twins, one twin per diet, meals delivered for the first 4 weeks
    Effect: body weight -4.2 lb (95% CI -7.3 to -1.3; metric: -1.9 kg, -3.3 to -0.6) vs omnivorous
    Certainty: Weight is a secondary outcome; the vegan group ate fewer calories.
    JAMA Netw Open, 2023 · checked 2026-10-07 · we read the abstract
11. ev-vegwl-11 · Observational data · prospective cohort with self-reported weight · n = 21966
    Multivariable-adjusted mean weight gain was somewhat smaller in vegans (284 g in men and 303 g in women, P<0.05 for both sexes) and fish-eaters (338 g, women only, P<0.001) compared with meat-eaters.
    
    Who: men and women aged 20-69 in the Oxford arm of EPIC, median follow-up 5.3 years
    Effect: mean annual weight gain 389 g men, 398 g women; vegans 284 g men, 303 g women (P<0.05)
    Certainty: Observational data, self-reported weight; a cohort that is healthy in behavior.
    Int J Obes (Lond), 2006 · checked 2026-10-07 · we read the abstract
12. ev-vegwl-12 · Position of an expert body · agency fact sheet · n = —
    Vegans who consume no animal products and vegetarians who consume some animal products (e.g., dairy products, eggs, or both) but not meat have a higher risk of developing vitamin B12 deficiency because natural food sources of vitamin B12 are limited to animal foods [3,57].
    
    Who: vegans and vegetarians
    Effect: higher risk of B12 deficiency; fortified foods and supplements substantially reduce the risk
    Certainty: Main caveat for those switching to a diet for weight.
    NIH Office of Dietary Supplements, Vitamin B12 fact sheet for health professionals · checked 2026-10-07 · we read the section
13. ev-vegwl-13 · Observational data · prospective cohort study · n = 54898
    Compared with meat eaters and after adjustment for socio-economic factors, lifestyle confounders, and body mass index (BMI), the risks of hip fracture were higher in fish eaters (hazard ratio 1.26; 95% CI 1.02-1.54), vegetarians (1.25; 1.04-1.50), and vegans (2.31; 1.66-3.22), equivalent to rate differences of 2.9 (0.6-5.7), 2.9 (0.9-5.2), and 14.9 (7.9-24.5) more cases for every 1000 people over 10 years, respectively.
    
    Who: EPIC-Oxford participants: 29,380 meat eaters, 8037 fish eaters, 15,499 vegetarians, 1982 vegans
    Effect: hip fracture HR vegans 2.31 (95% CI 1.66 to 3.22), vegetarians 1.25 (1.04 to 1.50); 14.9 more cases per 1000 over 10 years in vegans
    Certainty: Observational data; the estimate is already adjusted for BMI and lifestyle.
    BMC Med, 2020 · checked 2026-10-07 · we read the abstract
14. ev-vegwl-14 · Observational data · systematic review and meta-analysis of observational studies · n = 48626
    Although group averages for most nutrients and biomarkers remained within pediatric reference ranges, increased odds of iron deficiency and anemia were observed in lacto-ovo-vegetarians, and vitamin B12 deficiency in vegans.
    
    Who: children under 18 without chronic disease: 7280 lacto-ovo-vegetarians, 1289 vegans, 40,059 omnivores
    Effect: lower height, weight, BMI z-scores; increased odds of iron deficiency and anemia (lacto-ovo) and B12 deficiency (vegans)
    Certainty: Not for weight loss in children; a caution for a family switching to the diet.
    Crit Rev Food Sci Nutr, 2026 · checked 2026-10-07 · we read the abstract
15. ev-vegwl-15 · Meta-analysis or systematic review · umbrella review of systematic reviews and meta-analyses with GRADE · n = 8 RCTs
    For the general healthy population, a vegan diet was effective for reducing body weight [MD (95% CI): -2.52 kg (-3.06, -1.98), n = 8 RCTs; moderate CoE]
    
    Who: general healthy population; meta-analyses of observational and clinical studies
    Effect: body weight MD -5.6 lb (95% CI -6.7 to -4.4; metric: -2.52 kg, -3.06 to -1.98), 8 RCTs, moderate certainty
    Certainty: Level A: for weight (8 RCTs).
    Crit Rev Food Sci Nutr, 2023 · checked 2026-10-07 · we read the abstract
16. vgtn-r1-09 · Observational data · meta-analysis of observational studies · n = 4 studies, 1,994 participants
    Meta-analysis showed no significant differences in serum vitamin B12 levels (MD: -9.85 pmol/L; 95% CI: -45.64 to 25.94 pmol/L; P = 0.54, I2 = 50%) or daily intake (MD: 3.31 mcg/d; 95% CI: -4.70 to 11.32 mcg/d; P = 0.42, I2 = 90%) between plant-based Adventists and omnivore controls, although there was high heterogeneity between the studies.
    
    Who: 1,994 Seventh-day Adventists, vegan or vegetarian, with omnivore controls, in 4 observational studies
    Effect: serum B12 MD -9.85 pmol/L (95% CI -45.64, 25.94), intake MD 3.31 mcg/d (95% CI -4.70, 11.32); I2 50% and 90%
    Certainty: Adventists consume fortified foods more often than other vegetarians, transfer to the general population is not automatic
    Am J Health Promot, 2025 · checked 2026-09-23 · we read the abstract
17. vgtn-r1-10 · Observational data · meta-analysis of cross-sectional studies · n = 26 studies, 23,783 participants
    Adults who followed VVDs had moderately higher ON symptoms compared to omnivores (standardized mean differences using Cohen's d index = 0.46; 95% confidence interval [CI]: 0.33, 0.60; inconsistency index [I 2] = 81.0%)
    
    Who: 23,783 adults, 72.0% female, mean age range 19.6 to 51.0 years, in 26 cross-sectional studies
    Effect: standardized mean difference 0.46 (95% CI 0.33, 0.60), odds ratio 1.99 (95% CI 1.21-3.25); I2 81.0% and 92.8%
    Certainty: all included studies are cross-sectional and of low methodological quality, no causality
    Int J Eat Disord, 2026 · checked 2026-09-23 · we read the abstract