Self-Starvation of Rats in Running Wheels as a Function of Activity-Food Interval and Food Consistency

Rats under restricted food schedules are generally capable of maintaining stable body weights by reducing energy output. However, if they are given access to running wheels, they fail to respond with this adaptive strategy. Instead, they show an increase in activity and a paradoxical decrease in caloric intake, leading to the development of stomach ulcers and death. Since food-yoked controls kept in standard cages remain ulcer-free and survive, the formation of stomach lesions appears to be due to the combination of increased energy expenditure and insufficient food intake. The present study attempted to attenuate this self-starvation effect by providing more palatable food and by allowing a rest period between running and feeding. Subjects were fed either immediately or four hours after being removed from the wheel, and they were fed either dry or wet chow. Both groups receiving wet food survived, and only one rat in the delayed-dry feeding condition died. All five rats given access to dry chow immediately after running self-starved, whereas all other experimental subjects, with the one exception, met the survival criterion. Results are discussed in light of related theories.