New Study: Low-Fat Vegan Diet Boosts Metabolism, Leads to Weight Loss

In overweight individuals, a low-fat vegan diet can lead to weight loss, boost metabolism, and improve cardiometabolic risk factors, new research shows. The study, published in JAMA Network Open on Nov. 30, was led by the Physicians Committee for Responsible Medicine, with support from the Yale School of Medicine. 

Researchers conducted a 16-week randomized controlled trial of 244 overweight adults who had no history of diabetes. They divided the participants evenly into two groups: a control group, which continued with their typical eating patterns; and an intervention group, which adopted a low-fat vegan diet of vegetables, grains, legumes, and fruits, with no animal products or added fats. Both groups were instructed to exercise the same amount that they usually would.

Participants in the low-fat vegan group received some instruction on how to prepare foods, including weekly cooking demonstrations. 

After 16 weeks, those eating the low-fat vegan diet had lost an average of 13 pounds, while the control group had not lost a significant amount of weight. Researchers noted that the vegan group tended to eat fewer calories than they did prior to the trial (around 350 fewer each day, on average), even though they weren’t asked to restrict calories. This is likely a byproduct of whole plant foods’ low calorie-density. Another major factor in the weight loss: Those in the vegan group burned 18.7 percent more calories after meals on average than they had before switching diets. 

“These findings are groundbreaking for the 160 million Americans struggling with overweight and obesity,” says study author Hana Kahleova, MD, PhD, director of clinical research for the Physicians Committee. “Over the course of years and decades, burning more calories after every meal can make a significant difference in weight management.” 

Additionally, PCRM teamed up with researchers from the Yale School of Medicine to track lipids in muscle and liver cells for a subset of participants. After 16 weeks, those in the vegan group had lowered the fat in their liver cells by an average of 34 percent and the fat in their muscle cells by 10 percent, while the control group saw no significant changes. 

“When fat builds up in liver and muscle cells, it interferes with insulin’s ability to move glucose out from the bloodstream and into the cells,” Kahleova says. This can contribute to insulin resistance and heighten the risk for type 2 diabetes.

The study adds to a growing body of research suggesting that plant-based diets can promote weight loss and better cardiometabolic health.