The simplest answer to this question is, "it depends." Research studies do not show that an automatically increased rate of weight loss success can be brought about through vegetarian eating. In fact, a very recent study in this area showed pesco-vegetarians (who consumed plants and seafood) and semi-vegetarians (who followed plant-based diets, with infrequent intake of seafood and animals foods) to have an almost identical average rate of weight loss with meat eaters. However, with strict vegan eating (involving no intake of any animal foods or seafood), this relationship was found to change, with significantly better weight loss success in vegans versus meat-eaters (or other types of vegetarians). This difference in vegan success may not be entirely due to diet, however. Vegan participants in research studies are often more likely to engage in vigorous physical activity, and less likely to consume alcohol, than meat eaters or other types of vegetarians.

If you change this question slightly, and look not specifically at weight loss but at the extent of obesity among vegetarians versus non-vegetarians, vegetarians come out ahead. Using a body mass index (BMI) of 30 or greater as a criterion for clinical obesity, recent studies have found that approximately 33% of meat eaters are clinically obese, as compared with 27% of semi-vegetarians, 18% of pesco-vegetarians, 17% of lacto-ovo vegetarians, and 9% of vegans. In some of these studies, an additional very interesting finding has been the great similarity in calorie intake amount these different groups. This finding lends further support to the possibility of weight management advantages from vegetarian eating.

On a practical level, you are not going to improve your chances of weight loss or weight management by swapping animal foods for low-quality plant foods, or by bringing more plant foods into your diet in a random, unplanned way. Strictly in terms of calories, you are likely to increase your calorie intake by such an approach. For example, a cup of brown rice contains about 37% more calories than four ounces of salmon, and one cup of garbanzo beans contains about 71% more. Only one of our Top 10 highest calorie foods is an animal food (lamb). And only two of our Top 25 highest calories foods are animal foods (lamb and chicken). But if you broaden the context beyond calories, there are even more reasons why replacement of animal foods with low-quality plant foods does not make sense. Healthy metabolism is needed for successful weight management, and low-quality plant foods like heavily processed and refined grain products or reconstituted pulp-free fruit juices aren't likely to provide you with the nutrient support you need for healthy metabolism. Our WHFoods recommendations are as follows.

• If you already consume animals foods and enjoy eating them, don't remove them from your meal plan in order to lose or manage your weight. Instead, try to improve your animal food quality as much as possible and focus on a balanced overall diet that has the right number of calories to fit your lifestyle. You will find detailed information about animal food quality and calories in each of our individual food profiles for animal foods.
• If you are actively seeking to lessen your intake of animal foods, go ahead and do so. Vegetarian-type diets have repeatedly been shown to offer broad health-benefits. But once again, it is important to focus on a balanced overall diet that has the right number of calories to fit your lifestyle, and that is not plagued by nutrient deficiencies or excesses. We also recommend reading over our entire group of Q & As related to vegetarian eating, starting with A Practical Look at Vegetarian Diets.
• If you already follow a vegetarian approach but are having trouble with weight management, consider a meeting with your healthcare provider or nutritionist to help evaluate possible nutrient deficiencies and excesses. While your overall approach may be a very good one, there may be some nutritional imbalances that can be adjusted for greater success.

More Information on Vegetarian Diets

For more information on the subject of vegetarian diets, please see our overview article "A Practical Look at Vegetarian Diets" as well as the following Q+As.

• Are Vegetarian Diets Really More Healthful?
• What Do You Think About a Mostly Vegetarian-Plus-Seafood Meal Plan?
• What Do You Think About a Mostly Vegetarian-Plus-Dairy/Eggs Meal Plan?
• How Does Seafood Compare With Dairy/Eggs as a "Protein Booster" on a Vegetarian Diet?
• What Nutrients Are Most Likely to be Deficient in a Vegetarian Diet?
• How Much of a Problem is Protein in a Vegetarian Diet?
• How Much of a Problem is Iron in a Vegetarian Diet?
• Is Vitamin B12 Really a Problem in a Vegetarian Diet?
• Does WHFoods Directly Advocate a Vegetarian Meal Plan?
• What if I Eat Vegetarian Most of the Time, but Enjoy Meat and Poultry on Occasion?
• If I am Mostly Eating Plant Foods, do I Still Need to be Concerned About Food Quality?

References

To see the research articles we reviewed in the writing of these articles, see here.