Research
Energy balance
Vegetarian and vegan diets are consistently associated with a lower Body Mass Index (BMI) and slower weight gain over time compared to non-vegetarian diets, although obesity prevalence can still be high in specific subgroups.
Switching to a vegetarian or vegan diet often leads to a modest reduction in body weight (approx 1 kg/m2 BMI difference). Vegans tend to gain weight more slowly than vegetarians and meat-eaters. Focus on whole plant foods rather than refined carbs to maximize this benefit.
GoodSupportsHIGH confidence
Studies of Western vegetarians have consistently reported that vegetarians have a lower BMI than comparable non-vegetarians, with differences in mean BMI of about 1 kg/m2... Follow-up of body weight... shows a mean body-weight increase of approximately 400 g/year overall, with significantly lower weight gain in vegans, but not in vegetarians, than in meat-eaters.
Why this rating
Based on large cohort studies (EPIC-Oxford, n>20,000) and cross-sectional data.
Source
Health effects of vegetarian and vegan diets
Timothy J. Key et al. · Proceedings of The Nutrition Society · 2006
DOI 10.1079/pns2005481
narrative_reviewCited 406×
Read the paper DOI resolved against Crossref · corpus check 2026-06-10
More from this paper
- Adopting a vegetarian or vegan diet is associated with a moderate reduction in mortality from ischemic heart disease (IHD) compared to non-vegetarian diets, primarily driven by lower plasma cholesterol levels and lower body mass index (BMI).Good
- Vegetarian and vegan diets are associated with suboptimal Vitamin B12 status and elevated homocysteine levels, requiring careful monitoring and supplementation to avoid potential health risks.Good
- Vegetarian and vegan diets do not show clear differences in total mortality, stroke mortality, or cancer rates (colorectal, breast, prostate) compared to non-vegetarians, although IHD mortality is lower.Good
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