Sugars provide a strong, pleasant, sweet taste and at the same time deliver energy when ingested. Their effects on food intake and selection may therefore be a result of both their hedonic and their physiologic features. The theory that appetite signals arising from sugars are different from those arising from other carbohydrates because of sugars' sweetness has led to the hypothesis that sugars are a cause of excessive energy intake and obesity. However, experimental studies provide evidence that the ingestion of > or = 50 g sugar within 20-60 min of a meal results in reduced mealtime food intake, which suggests that appetite regulatory centers respond to sugar's energy content. Epidemiologic studies provide evidence that sugar consumption, as well as carbohydrate consumption, is associated with leanness, not obesity. Thus there is no evidence to support the hypothesis that sugar is unique among carbohydrates as a dietary component affecting food intake.