Plant-based diets high in carbohydrates reduce body weight and body fat and improve insulin function in overweight individuals, according to a small study.The study has important implications because more than 7 in 10 U.S. adults are considered overweight or obese, which is a considerable risk factor for developing diabetes.
“Fad diets often lead people to fear carbohydrates,” says lead study author, Dr. Hana Kahleova, director of clinical research for the Physicians Committee for Responsible Medicine. “But the research continues to show that healthy carbohydrates–from fruits, vegetables, beans, and whole grains–are the healthiest fuel for our bodies.”
In the 16-week randomized clinical trial, researchers assessed insulin resistance after a meal for 75 overweight participants without diabetes for 16 weeks, half of whom followed a low-fat, vegan diet. 72 participants (96%) completed the whole study. The plant-based diet group avoided all animal products and added oils. Their fat intake was limited to 20-30 grams per day. There were no limits on calories or carbohydrate intake.
The control group maintained their current diets, which included meat and dairy products. Neither group altered their exercise routines. Total carbohydrate intake did not change in the control group, but increased significantly in the plant-based diet group, both as absolute intake and as a percentage of total calories. Participants focused on whole, complex carbohydrates from fruits, vegetables, whole grains, and legumes.
At the end of the trial, body mass index, body weight, fat mass, visceral fat volume, and insulin resistance decreased significantly in the plant-based diet group. There were no significant changes in the control group.Kahleova says the results are statistically significant. “The higher the carbohydrate intake, the more weight the participants were losing, particularly fat and visceral fat,” she indicates.
As far as what was more important: the carb intake or the lack of animal products in the diet, Kahleova says both factors are important.“When people remove animal products from their diets, they tend to start eating more carbohydrates, as opposed to fat or protein,” Kahleova explains. “Complex carbohydrates are rich in fiber, which is only found in plant foods, which helps fill you up without adding any extra calories.”
By avoiding animal products, she says we not only consume more fiber, but we also tend to eat more nutrient-dense foods and less fat, saturated fat, and calories.Kahleova says that lower body fat increases beta-cells’ ability to regulate blood sugar. She says these results show that a vegan dietary intervention could help prevent diabetes.
Researchers say the study’s results support other findings that a plant-based, high-carbohydrate diet can help with weight regulation and body composition and reduce the risk for Type 2 diabetes.Complex carbohydrates are naturally rich in fiber–a nutrient found in plant foods that add bulk to the diet without adding extra calories.The study adds to the body of evidence showing that plant-based diets are effective for weight loss.
“Previous clinical trials have shown that people who switch to a plant-based diet lose weight, while epidemiological studies, including the Adventist Health Study, have shown that populations eating plant-based diets tend to be slimmer than those consuming animal products,” she adds.
Study authors were from: Physicians Committee for Responsible Medicine, CNR Institute of Neuroscience in Padua, Italy, the Institute of Endocrinology in Prague, Czech Republic, the School of Medicine, University of Utah, Salt Lake City, UT, and the George Washington University School of Medicine and Health Sciences, Washington, DC.The study was funded by the Physicians Committee for Responsible Medicine.The Physicians Committee for Responsible Medicine is a nonprofit organization encouraging the use of low-fat, plant-based diets and discouraging the use of animal-derived, fatty, and sugary foods.