AJP - Regulatory, Integrative and Comparative Physiology, Vol 254, Issue 6 877-R884, Copyright © 1988 by American Physiological Society
Metabolic and structural adaptations to exercise in chronic intermittent fasted rats
R. J. Favier and H. E. Koubi
Laboratoire de Physiologie, UA 621 and 181 Centre National de la Recherche Scientifique, Lyon, France.
The effect of repetitive alternance of 3 days fasting and 3 days refeeding
on morphological and biochemical ability to perform exercise was
investigated in adult male rats. At the end of 10 wk of chronic
intermittent fasting, the rats had consumed 20% less food but were able to
maintain their initial body weight. Intermittent fasted rats (IF) had
significantly lower carcass fat but had maintained the percent contribution
of proteins to total carcass weight. The relative mass of liver, heart,
kidney, and muscles was not affected by such dietary manipulation. Both
glycolytic and oxidative enzyme capacities were reduced in IF rat muscles.
In response to exercise (2 h of swimming), control rats displayed
hypoglycemia, whereas IF rats were able to maintain plasma glucose level in
spite of a reduced energy supply from liver (low glycogen stores) and
adipose tissue (low plasma free fatty acid levels). This had been obtained
by accumulating glycogen and triglycerides in muscles and by deriving
energy for muscular contraction from the in situ breakdown of these
energetic substrates. In addition, although IF rats displayed a markedly
reduced liver protein content, the liver exercise-induced protein breakdown
was abolished in these animals.
