Two studies were performed to evaluate the short-term effect of a high-fat diet on spontaneous energy intake and the respective contribution of diet composition and energy density of food. Ingestion of high-fat foods was associated with a significant increase in energy intake in the two studies (P less than 0.05). In study 1 this increase was accompanied by a reduction in total weight of food consumed when compared with values obtained under low-fat-diet conditions. Moreover, the occurrence of satiety coincided with a level of carbohydrate intake corresponding to the expected daily carbohydrate oxidation when high-fat foods contained a moderate amount of carbohydrates. In study 2, where the carbohydrate content of high-fat foods was unusually low (less than or equal to 25% of their energy content), carbohydrate intake was lower than usual carbohydrate oxidation. Under the conditions of this study, energy density of foods seemed to play a significant role on the occurrence of satiety.