Excessive Activity and Anorexia in Rats

When rats are fed one meal a day, they lose weight but soon adjust their food intake and survive. Interestingly, when these animals are exposed to the same food schedule and allowed to run on a wheel, they die of starvation (Epling et al. 1981, 1983). Wheel running becomes excessive if food is restricted and animals may complete more than 10000 turns per day, a distance equivalent to 10 km. This excessive activity interferes with feeding and causes a steady decline in body weight. As wheel running peaks, animals may stop eating — even though this is not required by the experimental procedures. We have called this process activity-based anorexia and we have argued that a similar anorexia occurs in humans (Epling and Pierce 1988).