Activity-based anorexia: relationship to gender and activity-stress ulcers.

The phenomena of activity-based anorexia (ABA) and the activity-stress ulcer (ASU) both involve paradigms in which the food intake of rats is restricted and the animals are allowed voluntary exercise in a running wheel. This study determined the susceptibility of male and female rats to ABA and ASU following 25- and 30-percent losses of their original body weights. Male rats reached both weight loss criteria in a fewer number of days than did female rats. None of the male and female rats sacrificed at the 25% weight loss criterion evidenced gastric lesions; 52% of the animals sacrificed at the 30% weight loss criterion had one or more lesions. No gender differences with respect to gastric lesions were observed at the 30% weight loss criterion; however, at both weight loss criteria, females ate and ran more than males. It is concluded that ASUs are a consequence rather than a cause of ABA, and that there is a sexually "dimorphic" susceptibility to ABA but not ASUs. The utility of using a 25% weight loss criterion for defining ABA is also discussed.