Preadaptation to the feeding schedule does not eliminate activity-based anorexia in rats

To test whether activity-based anorexia (ABA) still occurs after preadaptation to the feeding schedule, 20 rats were first exposed to a feeding schedule of one 90-min meal per day until adaptation occurred (measured by maintenance of stable body weight). Then, during ABA training, half the rats (wheel group) were confined in running wheels except during the daily meal, and half (cage group) were not. Wheel running suppressed feeding--that is, food intake in the wheel group was less than that in the cage group. Also, the rats in the wheel group lost weight, whereas those in the cage group did not. Wheel running increased over days. Thus, the defining characteristics of ABA were evident in rats that were not subjected to ABA training until after they had become well adapted to the feeding schedule. These findings support the view that the suppression of feeding produced by wheel running triggers the vicious circle of ABA. They also cast doubt on the hypothesis that activity-induced interference with adaptation to the feeding schedule plays a key role in causing ABA.