Altering the temporal distribution of energy intake with isoenergetically dense foods given as snacks does not affect total daily energy intake in normal-weight men

The objectives of the present study were to examine the effects of (1) inge sting mandatory snacks v. no snacks and (2) the composition of isoenergetic ally-dense snacks high in protein, fat or carbohydrate, on food intake and energy intake (EI) in eight men with ad libitum access to a diet of fixed c omposition. Subjects were each studied four times in a 9 d protocol per tre atment. On days 1-2, subjects were given a medium-fat maintenance diet esti mated at 1.6 x resting metabolic rate (RMR). On days 3-9, subjects consumed three mandatory isoenergetic, isoenergetically dense (380 kJ/100 g) snacks at fixed time intervals (11.30, 15.30 and 19.30 hours). Total snack intake comprised 30 % of the subjects' estimated daily energy requirements. The t reatments were high protein (HP), high carbohydrate (HC), high fat (HF) and no snack (NS). The order was randomized across subjects in a counterbalanc ed, Latin-square design. During the remainder of the day, subjects had ad l ibitum (meal size and frequency) access to a covertly manipulated medium-fa t diet of fixed composition (fat:carbohydrate :protein, 40:47:13 by energy) , energy density 550 kJ/100 g. All foods eaten were investigator-weighed be fore ingestion and left-overs were weighed after ingestion. Subjective hung er and satiety feelings were tracked hourly during waking hours using visua l analogue scales. Ad libitum EI amounted to 13.9 MJ/d on the NS treatment compared with 11.7, 11.7 and 12.2 MJ/d on the HP, HC and HF diets respectiv ely (F(3,21) 5.35; P = 0.007, SED 0.66). Total EI values were not significa ntly different at 14.6, 14.5, 15.0 and 14.2 MJ/d respectively. Snack compos ition did not differentially affect total daily food intake or EI. Average daily hunger was unaffected by the composition of the snacks. Only at 12.00 hours did subjects feel significantly more hungry during the NS condition, relative to the other dietary treatments (F(3,18) 4.42; P = 0.017). Body w eight was unaffected by dietary treatment. In conclusion, snacking per se l ed to compensatory adjustments in feeding behaviour in lean men. Snack comp osition (with energy density controlled) did not affect the amount eaten of a diet of fixed composition. Results may differ in real life where subject s can alter both composition and amount of food they eat and energy density is not controlled.