Have you recently lost some weight and are wondering what to eat to keep the weight off? According to a new study, eating low-glycemic foods helps maintain weight loss more so than eating a diet low in fat or carbs.
Researchers at the New Balance Foundation Obesity Prevention Center, Boston Children’s Hospital found that a low-glycemic diet had similar metabolic benefits to a very low-carbohydrate diet, but with less signs of physiological stress and chronic inflammation.
This long-term study, published in the Journal of the American Medical Association (JAMA), evaluated the effects of three diets on 21 overweight and obese men and women aged 18 to 40. The subjects lost 10 to 15 percent of their body weight initially. After the subjects’ weight stabilized, they were randomly assigned to one of the three diets, each for four weeks at a time.
- The low-fat diet had a high glycemic load and was designed to reflect conventional recommendations to decrease dietary fat.
- The very low-carbohydrate diet modeled the Atkins diet and had a low glycemic load due to the severe carbohydrate restriction.
- The low-glycemic diet focused on vegetables, legumes, and fruits that have a low to moderate effect on blood sugar levels. While a low-carbohydrate diet focuses on carbohydrate restriction, a low-glycemic diet emphasizes the carbohydrate source and promotes foods that reduce the increase in blood sugar after a meal.
Each diet had protein levels within the healthy, recommended range (10 to 35 percent of calories per day). The low-fat and low-glycemic diet provided similar amounts of fiber—about 30 grams per day—which meets the dietary guidelines for fiber. The opposite was true for the very low-carbohydrate diet, as only about three grams of fiber were given with each meal. Physical activity did not differ among the diet groups.
Although there were not significant differences in body weight between the three groups, changes in energy expenditure, or the amount of calories burned, differed significantly. The very low-carbohydrate diet had the greatest improvements in metabolism, followed by the low-glycemic diet. However, the very low-carbohydrate diet increased participants’ cortisol and C-reactive protein levels, whereas the low-glycemic diet did not. Cortisol excretion, a stress hormone, can promote adiposity, insulin resistance, and cardiovascular disease. C-reactive protein may also increase risk of cardiovascular disease.
The least effective diet, the low-fat diet, had the greatest decrease in calories burned and also showed signs of unhealthy fat accumulation and insulin resistance. The authors noted, “The low-fat diet produced changes in energy expenditure…that would predict weight regain.”
These results challenge the concept that “a calorie is a calorie” in terms of altering metabolism. Instead, this study suggests that certain macronutrients (fat, protein, and carbohydrates) can alter energy expenditure and have significant influence over weight regain.
“In addition to the benefits noted in this study, we believe that low-glycemic index diets are easier to stick to on a day-to-day basis, compared to low-carb and low-fat diets, which people may find limiting,” the researchers wrote in a press release. “Unlike low-fat and very low-carbohydrate diets, a low-glycemic index diet doesn’t eliminate entire classes of food, likely making it easier to follow and more sustainable.“
Only one in six overweight and obese adults report having maintained weight loss of at least 10 percent for one year. Declined motivation and lack of diet adherence are commonly linked to weight re-gain. A decrease in energy metabolism (calories burned) is also thought to play a major role in weight rebounding; however, the effect of dietary composition on energy expenditure during weight loss maintenance still merits more evidence.
Reference: Ebbeling CB, Swain JF, Feldman HA et al. Effects of dietary composition on energy expenditure during weight-loss maintenance. JAMA 2012;307:2627-34. doi:10.1001/jama.2012.6607