Moderate diet restriction alters the substrate and hormone response to exercise

Substrate and hormone responses to submaximal exercise were studied in 10 overweight women (119-141% ideal body weight) to learn if a moderately restricted diet would influence the responses. Subjects consumed diets with adequate energy (ADEX), N = 5, or low energy (LDEX)--50% reduction in energy, N = 5. Three times during the 12-wk study, blood was drawn before and immediately following exercise; results were combined since there were no differences between replicates. Postexercise free fatty acids and glycerol increased to 465 +/- 27 mg.l-1 in LDEX but only to 245 +/- 19 mg.l-1 in ADEX. Postexercise insulin increased to 129 +/- 13 pmol.l-1 in LDEX, but did not increase in ADEX. Postexercise growth hormone increased to 10.5 +/- 1.0 microgram.l-1 in ADEX but only to 6.6 +/- 1.0 microgram.l-1 in LDEX. All postexercise increases within diet groups were highly significant (P < 0.0001), and the postexercise responses between diet groups were also different (P < 0.01). Respiratory gas exchange indicated that both groups increased fat utilization during exercise, but diet restriction altered postexercise hormones so that fat mobilization and utilization might be inhibited. The postexercise recovery period should be studied further to determine whether diet restriction results in a sustained altered hormone pattern that would curtail lipolysis and possibly limit body fat loss.