The effects of prior weight reduction on the running wheel-induced feeding suppression in rats

Adult male rats given ad lib access to food and a running wheel show an initial feeding and weight suppression. Over 6-10 days feeding recovers, but body weight remains low. It is not clear which effect is primary, the wheel-induced feeding or weight change. To test this, rats were first restricted to 15g of food a day for 8 or 16 days to reduce their weight relative to control non-restricted rats. They were then returned to ad lib feeding and half the restricted and non-restricted control rats were introduced to the wheel either immediately (Experiment 1) or 4 days later (Experiment 2). Food intake, body weight, and wheel running were monitored throughout the experiments. At the return to ad lib feeding, prior food restriction elevated feeding. Both immediate and delayed wheel access suppressed feeding in both groups of wheel access rats compared to the appropriate control rats. Feeding history did not have a significant effect on wheel running. The wheel-induced reductions in feeding from baseline were similar in the weight reduced and normal weight animals suggesting that prior weight restriction did not prevent the onset of the wheel-induced feeding suppression. It is therefore suggested that the feeding suppression is not driven by a reduced weight set point.