Although a deficit in total energy intake relative to expenditure is the most critical dietary factor that determines weight loss, increasing evidence suggests that macronutrient composition of the diet may also influence weight loss and metabolic response (9). In a few previous studies, effects on atherogenic dyslipidemia and glycemic control have been observed to be more favorable with a lower versus higher carbohydrate diet, after adjusting for weight loss, in individuals with insulin resistance or type 2 diabetes (10–12).