Mortality rate and longevity of food restricted, exercising male
rats: a re-evaluation.
Holloszy, John O.
Division of Geriatrics and Gerontology, Department of Internal
Medicine, Washington University School of Medicine, St. Louis,
Missouri 63110
APStracts 3:0491A, 1996.
Food restriction increases the maximal longevity of rats. Male rats do
not increase their food intake to compensate for the increase in
energy expenditure in response to exercise. However, a decrease in
the availability of energy for growth and cell proliferation that
induces an increase in maximal longevity in sedentary rats only
results in an improvement in average survival, with no extension of
maximal life span, when caused by exercise. In a previous study, to
test the possibility that exercise prevents the extension of life
span by food restriction, wheel running and food restriction were
combined. The food-restricted runners showed the same increase in
maximal life span, as food-restricted sedentary rats, but had an
increased mortality rate during the first one-half of their mortality
curve. The purpose of the present study was to determine the
pathological cause of this increased early mortality. However, in
contrast to our previous results, 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 as to keep their body weights
the same as those of the runners. Thus, it is possible that the rats
in the previous study had a health problem that had no effect on
longevity except when both food restriction and exercise were
superimposed on it. Possibly of interest in this regard, the rats in
this study did considerably more voluntary running than those in the
previous one. It is concluded that a) moderate caloric restriction
combined with exercise does not normally increase the early mortality
rate in male rats, b) exercise does not interfere with the extension
of maximal life span by food restriction, and c) the beneficial
effects of food restriction and exercise on survival are not additive
or synergistic.
Received 10 July 1996; accepted in final form 22 October 1996.
APS Manuscript Number A646-6.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 13 November 1996