THE EFFECT OF COVERTLY MANIPULATING THE ENERGY DENSITY OF MIXED DIETSON AD-LIBITUM FOOD-INTAKE IN PSEUDO FREE-LIVING HUMANS

OBJECTIVE: This study examined the effects of covert alterations in th e energy density (ED) of mixed, medium fat (MF) diets on ad libitum fo od and energy intake (ED), subjective hunger and body weight ire human s. DESIGN: Randomised cross-over design. Subjects were each studied th ree times (factorial design), during 14d, throughout which they had ad libitum access to one of three covertly-manipulated NIF diets. SUBJEC TS: Six healthy men, mean age (s.e.m.)=30.0y (12.76y), mean weight=71. 67kg (19.80kg); mean height = 1.79 m (0.22 m), body mass index (BMI) = 22.36 (2.60) kg/m(2), were studied. The fat, carbohydrate (CHO) and p rotein in each diet (as a proportion of the total energy) and energy d ensity (ED) were, low-ED (LED), 38:49:13%; 373 kJ/100 g; medium-ED (ME D), 40:47:13%; 549 kJ/100 g; high-ED (WED), 39:48:13%; 737 kJ/101 g. S ubjects could alter the amount hut not:he composition of foods eaten. They were resident in (but not confined to) a metabolic suite througho ut the study. RESULTS: Solid food intake decreased as ED increased, gi ving mean values of 2.84, 2.51 and 2.31 kg/d, respectively. This was i nsufficient to defend energy balance, since energy intake increased wi th increasing ED (F(2,10) 16.08; P < 0.001) giving mean intakes of 10. 12, 12.80 and 16.17 MJ/d, respectively. Rated pleasantness of food (me asured on visual analogue scales) was not significantly different betw een diets nor was subjective hunger different between the LED, MED and HED diets, respectively. Diet significantly affected body weight (F(2 ,10) = 4.62; P = 0.038), producing changes of - 1.20, 0.02 and 0.95 kg , respectively, by day 14. CONCLUSION: Dietary ED can influence EI and body weight, since changes in amount eaten alone are insufficient to defend energy balance, where subjects feed on unfamiliar diets and die t selection is precluded. Comparison with our previous studies suggest that there was compensation in solid food intake when ED was altered using mixed diets (as in this study) compared to previous studies whic h primarily used fat or CHO to alter dietary ED.