Repeated short-fasting modifies the macronutrient self-selection pattern in rats.

The daily caloric intake and circadian pattern of macronutrient self-selection were examined in rats subjected to 3 h of food and water deprivation at the beginning or at the end of darkness. When one sole 3-h period of deprivation was applied, rats showed a compensatory response characterized by an unscheduled diurnal and nocturnal increase in the intake of the three macronutrients. However, repeated short restrictions during 15 days promoted a scheduled time-dependent feeding response, characterized by an exclusive increase in carbohydrate and fat intake and a decrease in protein intake. Repeated deprivation at the onset of dark produced a feeding response confined to the dark phase, while late dark deprivation produced both a diurnal and nocturnal increase in feeding. After 15 days of repeated restriction, rats showed no body weight variations with respect to control rats fed ad libitum. These results show that short fasting elicits a time- and macronutrient-dependent feeding response in rats, which involves reorganization of the macronutrient self-selection pattern to promote a total daily caloric compensation. These results suggest that animals principally respond to the energy deficit produced by restriction.