EFFECT OF EXERCISE OF LONGEVITY: STUDIES ON RATS
John O. Holloszy, MD
Washington University School of Medicine, St. Louis, MO
Numerous studies have shown that food restriction significantly increases maximal longevity in rodents. Exercise has a number of effects that are similar to those of food restriction. This similarity is most marked in male rats, which are unusual in that they do not increase their food intake to compensate for the increased energy expenditure caused by exercise. As a result, male rats that exercise regularly, starting early in life, are similar to food restricted rats in that they have growth retardation, a low body fat content, and reduced availability of energy for cell proliferation and growth. When sedentary, male rats are food restricted (~25-30% below ad libitum) to keep their body weight the same as that of voluntary wheel-running male rats, they have an extension of maximal life span. In contrast, the runners have no increase in maximal longevity. Thus, a relative energy deficit induced by food restriction is associated with an increase in maximum life span, while the same relative energy deficit induced by exercise does not result in extension of maximal longevity. When voluntary wheel running rats are food restricted, their maximal longevity is increased to the same extent as that of sedentary food restricted rats. It appears from these results that a) exercise has no effect on the rate of primary aging, b) slowing of primary aging by food restriction is not mediated by a decreased availability of energy, but by decreased intake and metabolism of food.
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