Since at least the mid-1980’s, scientists have found that vegetarians and vegans tend to weigh less than omnivores (meat-eaters). Decades later, whether adopting a vegetarian diet can lead directly to weight loss is still under scrutiny.
The Bottom Line on Vegetarianism and Weight Loss
- Vegetarians and vegans are less likely to be overweight and obese than those who eat meat.
- Cutting out red meat is associated with lower body weight
- It is unclear whether switching from to a vegetarian diet will necessarily cause weight loss; but there is some evidence that is does
- Switching to a vegetarian diet can lead to small weight losses, and these losses become more significant over time
- Experts recommend going vegetarian - or at least increasing plant foods and eating fewer animal products – to help weight control (Newby et al. 2005).
Studying Vegetarians and Their Diets
- A vegetarian diet is associated with low body weight and low body fat.
- Long-term maintenance of a meat-free diet might be the key to low body weight (Key & Davey, 1996).
1. In the UK, body mass index was 36% lower in males and 31% lower in females following a vegetarian diet compared to meat-eaters, even after taking into account other dietary variables like fibre, smoking, and alcohol (Appelby et al. 1998). Read more about BMI, a ratio of weight to height that estimates fatness.
2. A Swedish study found that those who avoid red meat (but eat poultry), lacto-vegetarians (dairy-consuming vegetarians) and vegans have a lower risk of being overweight or obese than omnivores (Newby et al. 2005).
- 40% of red meat-eaters were overweight.
- 29% of non-red meat eaters and vegans were considered overweight
- Only 25% of lacto-vegetarians met the cut-off for overweight
3. A study of vegetarian preschoolers found they were less likely to be obese than their non-vegetarian schoolmates (Dwyer et al. 1980).
4. Among college students, a vegetarian diet was maintained longer than a weight-loss diet (Smith et al. 2000).
Can Switching to a Vegetarian Diet Cause Weight Loss?
1. New vegetarians transitioning from an omnivorous diet over six months naturally decreased their energy intake (calories eaten)(Phillips et al. 2004).
- They had no changes in body weight but body fat decreased
2. Vegans and fish-eating women gained the least weight out a group of 21 966 health-conscious men and women who were followed over five years (Rosell et al. 2006).
- People who switched from being a meat-eater to fish-eater, from fish-eater to vegetarian, or from vegetarian to vegan gained the least amount of weight
- Differences between all groups were small but the smallest weights gains were among those who decreased their consumption of animal products
References:
Appelby M, Mann JI, and Key TJ. Low body mass index in non-meat eaters: the possible roles of animal fat, dietary fibre and alcohol. International Journal of Obesity and Related Metabolic Disorders. 1998; 22(5):454-60.
Dwyer JT, Andrew EW, Valadian I, and Reed RB. Size, obesity, and leanness in vegetarian preschool children. Journal of the American Dietetic Association. 1980; 77(4):434-9.
Key T and Davey G. Letters: Prevalence of obesity is low in people who do not eat meat. BMJ. 1996; 313:816-17.
Newby PK, Tucker KL, and Wolk A. Risk of overweight and obesity among semivegetarian, lactovegetarian, and vegan women. American Journal of Clinical Nutrition. 2005; 81:1267-74.
Phillips F, Hackett AF, Stratton G, and Billington D .Effect of changing to a self-selected vegetarian diet on anthropometric measurements in UK adults. Journal of Human Nutrition and Dietetics. 2004; 17(3):249-55.
Rosell M, Appleby P, Spencer E, and Key T. Weight gain over 5 years in 21 966 meat-eating, fish-eating, vegetarian, and vegan men and women in EPIC-Oxford. International Journal of Obesity. 2006; 30(9):1389-96.
Smith CF, Burke LE, and Wing RR. Vegetarian and weight-loss diets among young adults. Obesity Research. 2000; 8(2):123-9.
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