Role of corticosterone in adaptive changes in energy expenditure during refeeding after low calorie intake

We examined the importance of corticosterone in elevated efficiency of energy utilization during refeeding after low food consumption. Energy balance studies during refeeding (over periods of 14 or 16 days) were conducted in rats previously food restricted for 16 days at 50% of normal food intake. Comparisons made with nonrestricted weight-matched controls after validation studies indicated that 2-wk-younger weight-matched controls had similar maintenance energy requirements and similar efficiency of energy utilization above maintenance (i.e., net efficiency) to nonrestricted age-matched controls. Results indicate that relative to controls refeeding after low food consumption was associated with enhanced energy conservation underlain by a 16-18% reduction (P less than 0.001) in total energy expenditure over a 14-day period. This metabolic adaptation for energy conservation resulted in a threefold increase (P less than 0.001) in body fat accretion but no difference in body protein deposition. Bilateral adrenalectomy (ADX) 2 days before refeeding reduced differences in energy expenditure between refed group and controls from 18 to 8% (P less than 0.01) and attenuated body fat gain from a three- to twofold increase (P less than 0.001) above control group. Effects of ADX were prevented by daily corticosterone replacement. Data suggest that after a period of low calorie intake an adaptive neurohormonal switching mechanism facilitates replenishment of fat stores during refeeding. This metabolic reorientation (characterized by an adaptive fall in energy expenditure) has both an adrenal as well as a nonadrenal component, because it is partially reversed by prior bilateral ADX, an effect attributed to removal of corticosterone-induced inhibition of thermogenesis.