Most people regain the weight they lose from dieting within one or two years, in part because the body adapts by slowing metabolism and burning fewer calories. A meticulous study led by Boston Children's Hospital, in partnership with Framingham State University, now finds that eating fewer carbohydrates increases the number of calories burned. The findings, published November 14 in the BMJ, suggest that low-carb diets can help people maintain weight loss, making obesity treatment more effective.
The study, known as the Framingham State Food Study, or (FS)2, tightly controlled what people ate by providing them with fully prepared food-service meals for a 20-week period. Researchers carefully tracked participants' weight and measured insulin secretion, metabolic hormones and total energy expenditure (calories burned).
"This is the largest and longest feeding study to test the 'Carbohydrate-Insulin Model,' which provides a new way to think about and treat obesity," says David Ludwig, MD, PhD, who is co-principal investigator with Cara Ebbeling, PhD. (Ludwig and Ebbeling are co-directors of the New Balance Foundation Obesity Prevention Center in Boston Children's Division of Endocrinology.) "According to this model, the processed carbohydrates that flooded our diets during the low-fat era have raised insulin levels, driving fat cells to store excessive calories. With fewer calories available to the rest of the body, hunger increases and metabolism slows -- a recipe for weight gain."