Objective: To test whether overfeeding isoenergetic doses protein, carbohydrate and fat would differentially influence appetite on the same day, and the subsequent day's food intake.
Design: Six men were each studied three times on a 5-day protocol. On days 1 and 2 they were fed a medium fat (MF) maintenance diet (comprising 40:47:13% fat, CHO and protein by energy) calculated at 1.6 x RMR. Subjects entered the calorimeter at 08.00 on day 3 for 48 h. On day 3 (manipulation day), they ate a MF diet at 1.5 x RMR with an additional 0.6 x RMR as protein (HP), carbohydrate (HC) or fat (HF). On days 4 and 5, (outcome days), subjects had ad libitum access to isoenergetically dense MF (40:47:13) foods (550kJ/100 g). Subjective hunger and satiety were tracked hourly during waking hours throughout days 1-5.
Results: Throughout day 3 subjects felt significantly more full and less hungry on the high protein diet relative to the other two diets (P = 0.002). Also by the end of day 3 each overfed nutrient led to a significant increase in its own balance of the other two diets (P < 0.01). These effects did not influence the subsequent day's energy intake. The alterations in nutrient balance by the end of day 3 were partially buffered by increases in the oxidative disposal of each overfed macronutrient throughout day 4 (which was proportionately greater for protein (P < 0.001) than carbohydrate (P = 0.07) or fat (P = 0.1)).
Conclusions: HP diets were more satiating that isoenergetically-dense HC or HF diets on the day they are eaten. The HC diet was transiently more satiating than the HF diet after each meal. This study supports previous work which suggests that relatively large changes in nutrient balance produced on one day appear to be poorly compensated by changes in energy intake on a subsequent day in men.