Weight
Lower obesity risk, and more calories burned in digestion
LowestObesity risk of any diet group
Vegans have the lowest risk of obesity out of any diet group[1]. In trials, people on vegan diets lose more weight than people on other diets, even without counting calories[6][8], and their bodies burn more calories digesting food and store less fat in the liver and muscles[9]. Red and processed meat go the other way, with more obesity[7]. If you wanted to lose weight, you would stop eating animals.
What the evidence says
The main points first. Every claim is tied to a source below.
Vegans have the lowest obesity risk of the diets studied
Vegan diets are consistently linked with the lowest risk of obesity[1]. The reasons are simple: more fiber, foods that pack fewer calories into each bite, and less of the heavy fat that comes with animal products.
Read full article →Identical twins lost more weight on a vegan diet
In a randomized trial in JAMA Network Open, 22 pairs of identical twins were split up for 8 weeks, one twin eating a healthy vegan diet and the other a healthy omnivorous diet[1]. The vegan twins lost more weight, and their LDL cholesterol and fasting insulin improved more[1]. You don’t need animal products to lose weight, and losing weight often means getting fewer of your calories from them.
Read full article →In trials, people lost weight on plant-based diets even when weight loss wasn’t the goal
In a 16-week randomized trial, people on a vegan diet lost about 6.5 kg and shed visceral fat, the fat around the organs, while the control group didn’t change[1]. In the BROAD community trial, a whole-food plant-based diet lowered people’s BMI[2]. A meta-analysis of vegetarian-diet trials found that people lost weight on average, even in trials where weight loss wasn’t the stated goal[3].
Read full article →A vegan diet raised the calories burned digesting food by 14%
In a 16-week randomized trial of 244 overweight adults, a low-fat vegan diet cut body weight by 5.9 kg[1]. The trial left out people who already had diabetes[1]. The calories burned digesting food, known as the thermic effect of food, went up 14%, which helps explain the weight loss[1]. Liver fat fell 34% and muscle fat 10%, and insulin sensitivity improved, while the control group showed no change in any of these[1]. Across 11 trials lasting 12 weeks or more, vegan diets cut weight by 4.1 kg and HbA1c by 0.18 points[2]. In 12 trials, people assigned a vegetarian diet lost 2.0 kg more than those on comparison diets, and people on vegan diets lost 2.5 kg more[3].
Read full article →Red and processed meat are linked with 37% higher odds of obesity
Across 1,135,661 people, those who ate the most red and processed meat had 37% higher odds of obesity, along with a higher BMI and a bigger waist[1].
Read full article →Articles
Vegans have the lowest risk of obesity
Vegans have the lowest risk of obesity of any diet group, and in randomized trials, people put on a vegan diet lose weight even without counting calories, partly because their bodies burn more calories digesting the food.
Read full article →
Sources
Papers and datasets. Each card keeps its caveats, including small samples and single-animal cases.
[1]Obesity Reviews · Review
Vegan diets had the lowest obesity risk in a review of plant-based eating
Of the diets compared in this review, vegan diets were linked with the lowest risk of obesity.
[2]JAMA Network Open · Small sample
Identical twins lost more weight on a vegan diet than on an omnivorous one
In this 8-week randomized trial, 22 pairs of identical twins were split up, one twin eating a healthy vegan diet and the other a healthy omnivorous diet. The vegan twins lost more weight, and their LDL cholesterol and fasting insulin improved more.
[3]Nutrition & Diabetes, 2018 · Clinical
A 16-week low-fat vegan diet cut weight, fat mass, and insulin resistance
Overweight adults on a low-fat vegan diet lost 6.5 kg of body weight and 4.3 kg of fat mass, while people on the control diet saw no significant change. Visceral fat and insulin resistance (HOMA-IR) fell only in the vegan group.
[4]Nutrition & Diabetes, 2017 · Clinical
On a plant-based diet with no calorie counting, BROAD trial participants lost about 12 kg
The BROAD trial randomized people with obesity, ischemic heart disease, or type 2 diabetes, and the group on a whole-food plant-based diet didn’t count calories. After 6 months, they had lost about 12 kg, their BMI and cholesterol had improved, and their HbA1c had fallen. Two people with diabetes no longer met the threshold for a diagnosis.
[5]Journal of the Academy of Nutrition and Dietetics, 2015 · Meta-analysis
Vegetarian diets cut body weight in trials, even when weight loss wasn’t the goal
In clinical trials, people put on vegetarian diets, including vegan ones, lost weight on average, even in trials where weight loss wasn’t the stated goal.
[6]Journal of General Internal Medicine, 2016 · Meta-analysis
Vegetarian diets led to more weight loss in 12 trials, and vegan diets to even more
Across 12 trials, people assigned a vegetarian diet lost 2.0 kg more than those assigned non-vegetarian diets over a median of 18 weeks. On vegan diets, the difference was 2.5 kg.
[7]Obesity Reviews, 2014 · Meta-analysis
Eating more red and processed meat was linked with 37% higher odds of obesity
Across 1,135,661 people, eating more red and processed meat was linked with 37% higher odds of obesity. People at the top of the intake range also had a higher BMI and a larger waist circumference.
[8]Obesity Reviews, 2022 · Meta-analysis
Vegan diets cut weight and cholesterol in 11 trials lasting 12 weeks or more
Across 11 trials lasting at least 12 weeks in people with overweight or type 2 diabetes, vegan diets lowered body weight by 4.1 kg, BMI by 1.4, HbA1c by 0.18 points, total cholesterol by 0.30 mmol/L, and LDL cholesterol by 0.24 mmol/L. Blood pressure and triglycerides didn’t change.
[9]JAMA Network Open, 2020 · Clinical
A low-fat vegan diet cut weight and liver fat in a 16-week trial of 244 people
In a 16-week trial of 244 overweight adults, the trial left out people who already had diabetes. Those on the low-fat vegan diet lost 5.9 kg, and the calories their bodies burned digesting food (the thermic effect of food) rose 14%. Their liver fat fell 34%, the fat in their muscles fell 10%, and their insulin sensitivity improved. None of these changed in the control group.