Comparison of the satiety effect of protein, fat and carbohydrate preloads with the same energy, volume and palatability.

Numerous studies have shown that a protein proload more efficiently induces satiety than fat and carbohydrate. However, there are still some contradictions because of the diversity of designs employed: energy density, volume, palatability, texture of the preloads and the fact that they are common foods or not. The aim of this study was to compare the effect on satiety of different liquid preloads constituted only by protein, fat or carbohydrate in very controlled conditions. 56 subjects have participated to 4 randomised test days, one day per macronutrient and a control day. In each test day, they had to consume the preload entirely (245kcal; 250mL) and their food intake was mesured during the next meals. The volunteers were separed in two groups: the first one (T0) consumed the preload immediatly before lunch and the second one (T1) one hour before. Whatever the delay, no difference was found on food intake at lunch between the 3 different preloads. In the 2 groups, energy intake of preload and lunch was higher after lipid preload than in the control conditions. In the T0 group, the same result was observed with the protein preload. Our results do not confirm the higher satiety effect of proteins, may be because we used non common foods as preloads. According to the concept of learned satiety, the results could not be the same if the subjects were previously familiarised to the uncommon tested preloads.