USC study finds vegan diet most effective at weight loss

November 10, 2014

The below story was written by Joey Holleman and is reprinted here from The State.

Susan Reese lost 30 pounds and helped University of South Carolina researchers prove a point.

Reese was among the participants in a study to see which kind of diet was best for losing weight.
They were more interested in losing weight than backing a hypothesis. Many did both.

The study showed a strict vegan diet is more effective for losing weight than a vegetarian diet or those that include fish or red meat. Peer pressure and education about serving sizes and healthy cooking can drive weight loss, too.

“The support group was as important as the diet itself for me,” Reese said.

Everybody in the study conducted by the Arnold School of Public Health had access to the support groups, the diet education and the healthy recipes. But at the end of six months, the participants on the vegan diet lost more weight than the other groups by an average of 4.3 percent, or 16.5 pounds.

The study, published in The International Journal of Applied and Basic Nutritional Sciences, backed the idea that a diet eschewing animal products helps people shed weight.

Gabrielle Turner-McGrievy, the study’s lead author, knows a vegan diet isn’t right for everyone. It can be especially difficult to adapt in the first few weeks of moving away from meat, and finding meat-free recipes that suit your tastes can take time. But if you want to lose weight, a healthy vegan diet could be the best route.

One plus side is that vegan diets include carbohydrates. In fact, the USC study’s vegan diet was high in carbs.

“We’ve gotten somewhat carb-phobic here in the U.S. when it comes to weight loss,” Turner-McGrievy said. “This study might help alleviate the fears of people who enjoy pasta, rice, and other grains but want to lose weight.”

Turner-McGrievy expected the vegan diet would be the best for weight loss. But she was surprised the pesco-vegetarian diet ended up no better for weight loss than semi-vegetarian or omnivorous diets.

People volunteered for the study, not knowing which of the diet groups they would get. Those in the omnivorous diet could eat anything. The semi-vegetarian diet allowed some meat. The pesco-vegetarian diet excluded all meat except seafood. The vegetarian diet banned meat but allowed animal products such as cheese and eggs. The vegan diet allowed only plant-based foods.

When the participants gathered and found out which group they were in, “you could have heard a pin drop in the vegan group,” Turner-McGrievy said.

But only a few participants dropped out, and those were spread across all groups. Many, like Reese, were interested in anything that might help lose weight. She has been trying to drop a few pounds for years and has tried a variety of diets, and the USC study offered a free new diet alternative. (Participants actually were paid $20 if they stuck it out for the first two months.)

Reese was relieved she ended up in the vegetarian group rather than the vegan. She did fine without meat, but she would have missed cheese and eggs. Since the study ended, Reese has put back on about 10 pounds when changes in her job schedule made eating healthy more difficult. But she has stuck with the smaller portions and is eating much less meat than before participating in the study.

The diet study worked better than other diets for Reese because of the group sessions with Turner-McGrievy, who “has a personality that makes you want to please her,” Reese said. Turner-McGrievy also supplemented the education sessions with healthy snacks.

Reese’s competitive nature made her not want to let her group, or herself, down by gaining weight between weekly sessions. Another form of encouragement: She started feeling better as she dropped pounds.

Her co-workers noticed the difference, and she said some of them now are interested in participating in similar studies. By chance, Turner-McGrievy is recruiting for two more studies. One is for parents and their children ages 9-12 and the other is for adults who own an Android phone or tablet. Go to for more information.


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