Effects of exercise on longevity of rats.

It has been postulated that life span is inversely related to energy expenditure. If this is correct, regularly performed exercise could accelerate the aging process. In two early studies, exercise shortened the life span of rats; the results of these studies have been cited as evidence for the concept that an increase in energy expenditure accelerates aging. However, subsequent studies have not confirmed this finding. Instead, the weight of evidence now indicates that rats that exercise regularly have a longer average life span than sedentary, ad libitum-fed controls. Freely eating sedentary rats become obese, indicating that their food intake is in excess of their energy requirements. Available evidence seems compatible with the interpretation that exercise results in improved survival in rats by countering deleterious effects of a sedentary life combined with overeating.