Nemet, D., Connolly, P. H., Galassetti, P., Rose-Gottron, C., Larson, J. K., Pescatello, A. M., & Cooper, D. M. (2003) Nutrition plays a major role in the GH--UFG-I response to exercise. Medicine and Science in Sports and Exercise, 35(5), Supplement abstract 1362.

"Brief bouts of strenuous exercise can cause inhibition of the growth hormone (GH)--insulin-like growth factor-I (IGF-I) axis. Smith et al. (Metabolism 1987;36:533) showed that strenuous exercise training further reduced the circulating IGF-I when associated with a low calorie, low protein diet. But after 5 weeks of training, children and adolescents even with unrestricted access to food demonstrated reduced circulating levels of IGF-I (Pediatric Res 2002;52:491). These observations led us to hypothesize that exercise training would lead to a reduction in circulating IGF-I even under conditions of clearly adequate calorie and protein intake" (p. S244). This investigation assessed the hypothesis that a catabolic-type hormonal response (i.e., a decrease in IGF-I) will invariably occur with strenuous exercise training even if caloric intake exceeds total energy expenditure.

Males (N = 22) were examined for the combined influence of diet and exercise training on growth mediators and inflammatory cytokines during a 7-day strenuous exercise program (3 hr/day). Ss were assigned to a positive or a negative energy balance group.

19 Ss completed the study (9 restricted, 10 supplemented). The restricted group had an average weight loss while the supplemented group gained weight. IGF-I initially decreased in both groups; but from day 3 it continued to decrease only in the restricted group. The authors' hypothesis was refuted.

Implication. Diet may prevent or lessen the initial catabolic response associated with exercise. Diet plays a major role in the regulation of longer term GH?IGF-I response to strenuous exercise.

Return to Table of Contents for this issue.