Energy expenditure of rats subjected to long-term food restriction

Food restriction, even when expressed per unit of metabolic mass, leads to energy conservation as seen by decreased oxygen consumption. The objective of the present study was to verify whether the energy conservation mechanis m reduces energy expenditure for as long as food restriction lasts or wheth er a return to basal level may occur without realimentation, mainly in mild ly food-restricted rats. Wistar rats were brought to the laboratory on wean ing. They were then assigned to control group that received ad libitum food intake, R-10 and R-20 groups that received 90 and 80%, respectively, of th e food eaten by control group and R-M group that received an amount of food enough only to keep body weight. The food restriction period lasted for 3 months and was followed by another month during which all groups received a d libitum food intake. The results showed that even in animals subjected to mild food restriction (10%) there was a sustained decrease in oxygen consu mption that lasted until refeeding of the animals. The results led to the c onclusion that the energy conservation mechanism is active from little food restriction until more stronger levels of restriction, in a proportional m anner, and the decreased energy expenditure is maintained during the whole food restriction period.