Legumes for the Win: A Weight-Loss Trial Shows Their Power

Legumes included all types of beans, lentils and peas. In the media, legumes have been questioned as to whether they cause harm through pathways of inflammation triggered by lectins that can be found in these foods. The actual science and randomized trial data to support the "lectin" story is nearly absent but many people choose to avoid these healthy foods. In the recent Global Burden of Disease study report, legumes, whole grains and nuts were the 3 food types most associated with longevity. How about weight loss?

In a new scientific paper, 219 healthy, community-based adults in the Washington, DC, area, with a body mass index (BMI) between 28 and 40, were randomly assigned to either follow a low-fat vegan diet or make no diet changes for 16 weeks. .

Intervention: A low-fat, vegan diet deriving approximately 10% of energy from fat, with weekly classes including dietary instruction, group discussion, and education on the health effects of plant-based nutrition. Control group participants continued their usual diets.

Results: Fruit, vegetable, legume, and whole grain intake significantly increased in the vegan group. Intake of meat, fish, and poultry; dairy products; eggs; nuts and seeds; and added fats decreased. Decreased weight was most associated with increased intake of legumes and decreased intake of total meat, fish, and poultry. Those consuming a low-fat vegan diet also increased their intake of carbohydrates, fiber, and several micronutrients. There were also improvements in the low-fat vegan diet arm of the trial for  fat mass (decreased) and insulin resistance (decreased).

Conclusions: When compared with participants' usual diets, intake of plant foods increased, and consumption of animal foods, nuts and seeds, and added fats decreased on a low-fat vegan diet. Increased legume intake was the best single food group predictor of weight loss.

These data suggest that increasing low-fat plant foods and minimizing high-fat and animal foods is associated with decreased body weight and fat loss, and that a low-fat vegan diet can improve measures of diet quality and metabolic health. Legumes can be a major part of a healthy diet associated with weight loss and improved insulin sensitivity. 

Dr. Joel Kahn

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