An analysis of excessive running in the development of activity anorexia.

Food restriction combined with activity wheel access produces activity anorexia: a combination of excessive running, reduced food intake and rapid weight loss. Temporal distributions of running in activity anorexia were examined in a reversal design with one of 2 x 2 x 2 factorial combinations (pelleted-vs-powdered food x deprivation x wheel access) as the treatment condition. Wheel revolutions were recorded in 30 min intervals; body weights, food and water intakes were measured daily. Only wheel access combined with food deprivation reliably produced activity anorexia. Excessive running occurred in the absence of schedule-induced polydipsia, was unaffected by food form, and showed distributional characteristics of facultative behavior. These results are inconsistent with schedule-induced behavior explanations. Running distributions appeared consistent with chronobiological models with light/dark onset and feeding serving as zeitgebers.