It’s not just that vegetarians don’t eat meat—they’re generally prone to possessing a successful secret weapon (or two) that prevents them from packing on pounds. Thomas Moore, MD explains in The DASH Diet for Weight Loss.
A well-balanced vegetarian diet is rich in vegetables, fruit, whole grains, and legumes and low in fat. The main meals are comprised largely of bean or soy dishes, vegetables, and whole grains.
It’s true that meat—and red meat in particular—contains much more high-calorie saturated fat than a lot of other foods. However, it’s not just because they don’t eat meat that vegetarians are less likely to be overweight or obese. People who have chosen a vegetarian diet tend to pay attention to other areas of their health. They often exercise more and don’t smoke. Just as important, if they have been practicing a vegetarian diet for some time, they will have developed skills and knowledge about how to eat a vegetarian diet that is both meat-free and lower in calories than the regular American diet.