DIET AND INSULIN-LIKE GROWTH FACTOR-I IN RELATION TO BODY-COMPOSITION IN WOMEN WITH EXERCISE-INDUCED HYPOTHALAMIC AMENORRHEA

To assess the potential influence of diet and endogenous peptide anabolic hormone secretion on exercise-related differences in body composition, we compared levels of macronutrient intake, insulinlike growth factor I (IGF-I), andfat-free mass (FFM) and fat mass (FM) in matched groups of exercising women with and without secondaryhypothalamic amenorrhea. Women were tightly matched according to somatotype and grouped into those with exercise amenorrhea (EXam, n = 6), exercise eumennorhea (EXeu, n = 5), and sedentary eumennorheic controls (SED, n = 5). Although no between-group difference was observed in FFM, the EXeu subjects had a significantly lower fatfraction and a significantly elevated FFM/FM ratio. Kilocalorie and protein intakes did not differ between groups, butdietary fat intake was lowest and carbohydrate intake highest in the EXam subjects. Dietary macronutrients were notcorrelated with the FFM/FM ratio. However, levels of insulinlike growth factor I were significantly correlated to theFFM/FM ratio and there was a clear trend for the hormone to be highest in the EXeu subjects. We conclude thatdifferences in body composition between exercising women with and without exercise-induced hypothalamic-pituitary dysfunction were related to an alteration in IGF-I secretion, although differences in macronutrient intakemight also be a factor. Further studies are warranted to elaborate upon the dietary and hormonal factors regulating thebody composition response to exercise. © American College of Nutrition.