EFFECT OF HYPERCALORIC VERSUS ISOCALORIC LIPID DIET RATION ON DIURNALNOCTURNAL EATING PATTERN IN SELF-SELECTING RATS

Analyses of rats diurnal/nocturnal feeding behaviour were made accordi ng to the caloric density of the lipid ration. Adult male Sprague-Dawl ey rats were simultaneously offered three pure macronutrient diet rati ons: protein, carbohydrate, and lipid. The last was either kept isocal oric to protein and carbohydrate rations or was hypercaloric. Measurem ents of the food intake were recorded at 12-h intervals with respect t o the dark phase and to the light phase of the circadian cycle (24 h). Rats fed the hypercaloric lipid diet ration showed a significantly hi gher total energy intake compared with animals fed the isocaloric lipi d diet ration. Also, in the hypercaloric group, the percentage of ener gy ingested as protein was significantly higher during both the light and dark phases, whereas the percentage of energy ingested as carbohyd rate was significantly lower during the light phase and the 24-h cycle when compared with that of the isocaloric group. These results indica te that the caloric density of the lipid diet ration has differential effects on the diurnal/nocturnal energy intake and macronutrient choic e and suggest that these feeding patterns may modify the outcome of ex periments using macronutrient diet rations with different caloric dens ity.