Similar effects of foods high in protein, carbohydrate and fat on subsequent spontaneous food intake in healthy individuals

Pre-loads high in protein, as compared to carbohydrate and fat, produce greater satiety and reduce food intake after a fixed time interval. This study investigated the effect of macronutrient composition on spontaneous eating behaviour. On four separate occasions, 16 fasted, healthy, non-obese men, blinded to the true purpose of the study, consumed iso-energetic (∼3 MJ) yoghurt-based pre-loads of equivalent weight (∼0.5 kg), high in fat (40%) [HF], carbohydrate (60%) [HC] or protein (29%) [HP], and no pre-load in a randomized, single-blind fashion. Subjects ate at will from a selection of food items for the remainder of the day (7 h) with the time of food requests (h) and energy content (kJ) and macronutrient distribution (%) of food eaten recorded. The three pre-loads delayed the first spontaneous request for food by 1.5–1.8 h relative to no pre-load. Total spontaneous food intake was suppressed 29% [HP], 20% [HF] and 17% [HC] by the pre-loads. Neither the amount of food eaten per spontaneous eating episode, nor the spontaneous eating frequency differed statistically following ingestion of the different pre-loads or no pre-load. In this study, in subjects who were free to choose when as well as how much they ate, a high-protein pre-load exerted similar effects on satiety as did iso-energetic high-fat and high-carbohydrate pre-loads.