Low-fat, high–complex carbohydrate diets have been recommended to prevent obesity and promote weight loss; however, the efficacy of these diets consumed with no overt attempt at energy restriction remains controversial. In a randomized 14-week intervention trial, Hays et al compared the influence of a control diet, a low-fat, high–complex carbohydrate diet, and a low-fat, high–complex carbohydrate diet plus exercise on body weight and composition in 34 individuals aged 56 to 78 years. None of the groups significantly reduced their total energy intake over time. The 2 groups consuming the low-fat, high–complex carbohydrate diet lost more weight and percent body fat compared with controls. High carbohydrate intake did not result in decreased resting metabolic rate or reduced fat oxidation. These results show that a reduction in dietary fat without overt energy restriction or change in energy intake is an effective means of promoting weight loss in overweight individuals.