Mortality rate and longevity of food-restricted exercising male rats: a reevaluation

Holloszy, John O. Mortality rate and longevity offood-restricted exercising male rats: a reevaluation.J. Appl. Physiol. 82(2): 399-403, 1997.Food restriction increases the maximal longevity of rats. Malerats do not increase their food intake to compensate for the increasein energy expenditure in response to exercise. However, a decrease inthe availability of energy for growth and cell proliferation thatinduces an increase in maximal longevity in sedentary rats only resultsin an improvement in average survival, with no extension of maximallife span, when caused by exercise. In a previous study (J. O. Holloszyand K. B. Schechtman. J. Appl. Physiol. 70: 1529-1535, 1991), totest the possibility that exercise prevents the extension of life spanby food restriction, wheel running and food restriction were combined.The food-restricted runners showed the same increase in maximal lifespan as food-restricted sedentary rats but had an increased mortalityrate during the first one-half of their mortality curve. The purpose ofthe present study was to determine the pathological cause of thisincreased early mortality. However, in contrast to our previousresults, the food-restricted wheel-running rats in this study showed no increase in early mortality, and their survival curves were virtually identical to those of sedentary animals that were food restricted so asto keep their body weights the same as those of the runners. Thus it ispossible that the rats in the previous study had a health problem thathad no effect on longevity except when both food restriction andexercise were superimposed on it. Possibly of interest in this regard,the rats in this study did considerably more voluntary running thanthose in the previous study. It is concluded that1) moderate caloric restrictioncombined with exercise does not normally increase the early mortalityrate in male rats, 2) exercise doesnot interfere with the extension of maximal life span by foodrestriction, and 3) the beneficialeffects of food restriction and exercise on survival are not additiveor synergistic.