An increased intake of legumes and a decreased intake of meat, fish, and poultry can help individuals lose weight, according to a new study published in the medical publication Journal of the Academy of Nutrition and Dietetics

The 16-week study, undertaken by the nonprofit research and advocacy group Physicians Committee for Responsible Medicine (PCRM), included 244 overweight adults who were randomly assigned to either make no diet changes or to follow a low-fat vegan diet, without restrictions and consisting of vegetables, grains, legumes, and fruit. Researchers tracked the participants’ diet quality, body weight, fat mass, and insulin sensitivity. The final data analysis included 219 participants who completed the whole study and submitted their final diet records.

The study found that participants on the vegan diet lost an average of 13 pounds and 9.1 pounds of fat mass. Comparatively, body weight and fat mass did not decrease in the group that made no diet changes. In the vegan group, increases in fruit, legumes, meat alternatives, and whole grain intake and decreases in animal products, added oils, and animal fats were associated with weight loss. Notably, an increased consumption of legumes was associated with decreased weight, fat mass, and visceral adipose tissue (the hormonally active component of total body fat). Increased intake of fruit and meat alternatives were associated with a decrease in body weight, and increased consumption of whole grains was associated with decreased body weight and fat mass. 


When it came to animal products, the study noted that a decreased intake of eggs was correlated with decreased weight, and a decrease in high-fat dairy intake was associated with decreased weight and fat mass. Reductions in the combined intake of total meat, fish, and poultry were associated with weight loss and a decrease in fat mass. And decreases in the intake of added animal fats as well as added oils were associated with decreases in weight and fat mass. 

A vegan diet reduces risk of chronic disease

The researchers also noted that the vegan group experienced improvements in insulin sensitivity. Additionally, the vegan group’s diet quality, measured by the Alternative Healthy Eating Index-2010 (AHEI) score, increased by six points on average in contrast to no significant change in the group that did not make a diet change. 

The AHEI was developed by researchers at the Harvard School of Public Health to identify dietary patterns associated with lower risk of chronic disease. The index is composed of foods to eat more often, such as fruit and vegetables, and those to eat less often, such as red and processed meat. The higher the AHEI score, the lower the risk for chronic disease.

“Our research shows that the best way to improve the quality of your health is to improve the quality of the foods you eat,” Hana Kahleova, MD, PhD, director of clinical research at PCRM and study co-author, said in a statement. “That means avoiding animal products and eating a vegan diet rich in fruits, vegetables, grains, and beans.”


Does a vegan diet help you lose weight?

Similar studies done in the past have linked a vegan diet with weight loss. Research presented earlier this year by the Steno Diabetes Center at the European Congress on Obesity found that switching to a vegan diet for three months can lead to “meaningful” weight loss and lowered blood sugar. For this study, researchers in Denmark conducted a systematic review and meta-analysis of 11 randomized trials involving 796 individuals—who were overweight and/or diagnosed with Type 2 diabetes—in which they compared the effect of vegan diets (followed for a minimum of 12 weeks) to other types of diets on cardiometabolic risk factors such as body weight, body mass index, blood sugar levels, blood pressure, cholesterol, and triglycerides. 

In another 16-week crossover study published last year, researchers from PCRM compared weight loss results between groups following a low-fat vegan diet and those on a Mediterranean diet. The researchers found that participants lost an average of approximately 13 pounds on the vegan diet, compared with no mean change on the Mediterranean diet.

“Previous studies have suggested that both Mediterranean and vegan diets improve body weight and cardiometabolic risk factors, but until now, their relative efficacy had not been compared in a randomized trial,” Kahleova said. “We decided to test the diets head to head and found that a vegan diet is more effective for both improving health markers and boosting weight loss.”

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