Not necessarily. A vegetarian diet is not inherently a weight-loss diet but rather a lifestyle choice.
It is true, however, that adults and children who follow a vegetarian diet are generally leaner than nonvegetarians. This may be because a vegetarian diet typically includes less saturated fat and emphasizes more fruits, vegetables, whole grains and plant-based proteins — foods that are more filling and less calorie dense.
But a vegetarian diet isn't automatically low calorie. You can gain weight on a vegetarian diet if your portion sizes are too big or if you eat too many high-calorie foods, such as sweetened beverages, fried items, snack foods and desserts. Even some foods marketed as vegetarian can be high in calories and fat, such as soy hot dogs, soy cheese, refried beans and snack bars.
The basics of achieving and maintaining a healthy weight are the same for vegetarians and nonvegetarians: Eat a healthy diet and balance calories eaten with calories burned.