Why are vegans often thin?
Created on: September 16, 2026
Last edited on: September 16, 2026
Vegans are not automatically thin. However, some studies show a lower average BMI in people who eat a vegan diet. One possible reason: A whole-food plant-based diet often contains many high-fiber foods with low energy density. This can promote satiety and potentially contribute to lower calorie intake. The long-term energy balance remains crucial for weight gain or loss.
Do vegans actually have a lower BMI?
In an analysis of the Adventist Health Study-2, people with vegetarian and vegan diets had a lower BMI on average than people with mixed diets. However, this does not mean that every vegan is thin, nor does it mean that a vegan diet leads to underweight.
In the study mentioned, the group classified as vegan had an average BMI of 23.6, which was 5.2 BMI points lower than people with mixed diets, who had an average BMI of 28.8. For reference: A value of 18.5 to 24.9 is considered normal weight in adults. So we see: The group classified as vegan was, on average, not underweight, but within the normal weight range. However, since these are observational data, it cannot be concluded that the vegan diet alone was the cause of the lower BMI.
Why can a vegan diet promote a lower body weight?
Many typical foods in a whole-food fully plant-based diet - such as vegetables, fruits, potatoes, legumes, and whole grains - have a rather low energy density. This means they provide relatively few calories in relation to their relatively high volume.
Additionally, a plant-based diet is often quite rich in fiber. Fiber can contribute to a longer-lasting feeling of fullness. Those who feel full longer may consume fewer calories overall. Over a longer period, this can lead to a lower body weight.
Given the high prevalence of obesity in Western countries, there are also strong arguments - from a population-level perspective - for viewing a balanced, plant-forward diet as a sensible general guideline. Thus, the BNF explicitly recommends a mainly plant-based diet.
Does a vegan diet automatically make you thin?
No. French fries can be vegan. Cookies can be vegan. So can chocolate, chips, ice cream, and numerous convenience foods. The label "vegan" simply means that a food contains no animal ingredients.
The crucial point is: "Vegan" does not automatically make you thin. The specific food choices, total caloric intake, exercise, and other individual factors are decisive. Therefore, you can eat vegan and lose weight, maintain weight, or gain weight. The energy balance remains the most important factor in the long term:
- Calorie deficit: You eat fewer calories than you burn and lose weight.
- Calorie surplus: You eat more calories than you burn and gain weight.
Can you gain weight and build muscle on a vegan diet?
Yes. If you want to gain weight on a purely plant-based diet, you primarily need sufficient energy and, for muscle building, enough vegan protein sources as well as an appropriate training stimulus.
More energy-dense plant-based foods can be helpful, for example:
- Nuts and nut butter
- Tahini
- Avocados
- Plant oils
- Energy-rich smoothies and shakes
Summary: Why are vegans often thin?
Some studies show that people with vegan eating patterns have a lower average BMI. However, this is not automatic: A vegan diet can be designed for weight loss, weight maintenance, or weight gain. A vegan who primarily eats vegetables, legumes, and whole grains eats entirely differently from someone whose diet mainly consists of vegan fast food and sweets. Therefore, the statement "vegans are thin because they eat vegan" is an oversimplification.
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