Exercise, diet, and the reinforcing value of food in an animal model of anorexia nervosa.

Activity-based anorexia (ABA) develops when laboratory rats are subjected to a single meal per day and have access to an activity wheel for the remaining time. Here, we studied the contribution of exercise and diet to the reinforcing value of food during ABA development. Three groups of eight adult male Wistar rats were used: an ABA group with 21.5 hr (then 22 hr) of wheel access and 1 hr (then 30 min) of food access, a control group with the same time exposure to food but without exercise, and a yoked group to the ABA in terms of weight loss. Rats were daily tested on a progressive-ratio schedule to measure their motivation for food. ABA rats gradually reduced their body weight more than the food control group. Animals steadily increased their breaking points in parallel to losses in body weight, but no significant differences were found between groups. Adult rats can develop ABA, but their loss in weight neither resulted in a decrease of food intake nor in the motivation to obtain it.