Effects of a Low–Glycemic Load vs Low-Fat Diet in Obese Young Adults

WITH PREVALENCE APproaching one third of the population, obesity is among the most important medical problems in the United States and identification of effective dietary treatment has become a major public health priority. Three popular diets—low fat, low carbohydrate, and low glycemic load—have recently received much attention. However, clinical trials have produced inconsistent findings, with some suggesting that one diet is superior for weight loss and others indicating no difference between diets. This inconsistency may arise from methodological problems both within and between trials, such as different treatment intensity between groups, inadequate attention to treatment fidelity, variable nutrition education and dietary counseling strategies, and confounding by dietary and nondietary factors. An alternative explanation for this inconsistency relates to inherent physiological differences among study participants. One physiological mechanism that might relate weight loss to dietary composition is individual differences in insulin secretion. Diets with a high glycemic load (the mathematical product of the glycemic index and the carbohydrate amount) result in higher postprandial insulin concentration, caloAuthor Affiliations: Department of Medicine, Children’s Hospital Boston, Boston, Mass. Corresponding Author: David S. Ludwig, MD, PhD, Children’s Hospital Boston, 300 Longwood Ave, Boston, MA 02115 (david.ludwig@childrens.harvard.edu). Context The results of clinical trials involving diet in the treatment of obesity have been inconsistent, possibly due to inherent physiological differences among study participants.