EXERCISE INCREASES AVERAGE LONGEVITY OF FEMALE RATS DESPITE INCREASED FOOD-INTAKE AND NO GROWTH-RETARDATION

In previous studies, male rats given access to voluntary running wheels showed improved survival. Because the male runners did not increase food intake, it was not clear whether their improvement in average longevity was due to decreased availability of energy for cell proliferation and growth or to another effect of exercise. In this study, female rats, which increase their food intake in response to wheel running, were used to determine whether exercise can increase longevity when availability of energy for cell proliferation and growth is not decreased. At age 5 mo, the female voluntary wheel runners were running 9173 +/- 3640 m/day (mean +/-SD); running distance declined to 965 +/- 483 mld by age 34 mo. From 5 mo to 10 mo of age, the runners ate approximately 37% more than the sedentary rats. Thereafter, the runners ate approximately 20% more. The runners and sedentary rats attained similar peak body weights. However, the runners gained weight more rapidly, attaining steady state by 11 mo; the sedentary rats' weights did not plateau until approximately 15 mo. The runners had a significant prolongation of average longevity without an increase in maximal life span. The sedentary rats' average age at death was 924 +/- 155 days (mean +/- SD; range, 619-1263 d) compared to 1009 +/- 132 days (range, 693-1259 d) for the runners, p < .001. These results show that exercise improves average longevity of rats independent of decreased availability of energy for cell proliferation and growth. They also provide evidence that an increase in food intake is not harmful when balanced by an increase in energy expenditure.