Relationship Between Body Composition and IGF-I During Us Army Basic Combat Training

Body composition is a central component of health and insulin-like growth factor-1, a hepatic-derived hormone that mediates cellular anabolism and considered a biomarker of health status, is associated with differential changes in lean mass in response to disparate military training in male and female Soldiers. However, the directionality of the IGF-I and body composition relationship is not well described, and nor has it been thoroughly explored in both sexes in response to the same military training, while controlling for interrelated factors. PURPOSE: To examine the relationship between body composition and IGF-I in young men and women attending US Army Basic Combat Training (BCT). METHODS: Body composition and total serum IGF-I were measured during week 1 and week 9 of BCT (n = 1,206, M = 809, F = 397). Paired samples t-test were used to determine the change in body weight, body composition (lean mass, fat mass) and IGF-I during BCT (pre to post BCT). Pearson product-moment correlations and estimated partial correlations were used to estimate the correlation while controlling for pre-BCT lean mass, pre-BCT fat mass, pre-BCT IGF-I, and change in IGF-I. RESULTS: Pre-BCT lean mass (r = 0.05, p = 0.08) and fat mass (r = 0.05, p = 0.08) were not associated with pre-BCT IGF-I. During BCT, there was a decrease in body weight (PRE: 74 ± 14, POST: 72 ± 11 kg, p < 0.001), fat mass (PRE: 18 ± 7, POST: 15 ± 5 kg, p < 0.001) and an increase in lean mass (PRE: 52 ± 10.5, POST: 54 ± 10 kg, p < 0.001) and IGF-I (PRE: 176 ± 50, POST: 200 ± 50 ng/mL, p < 0.001). Change in lean mass was correlated with change in IGF-I (r = 0.1712, p < 0.001). Change in fat mass was correlated with changes in IGF-I (r = 0.0964, p = .002). Partial correlations indicated increases in IGF-I during BCT were associated with both increased lean mass (r = 0.08) and fat mass (r = 0.11), but those were not influenced by sex. CONCLUSION: We found changes in IGF-I and body composition are weakly associated and not driven by sex. We also found pre-BCT IGF-I had a weak positive correlation with pre-BCT lean mass, but not pre-BCT fat mass. This data indicates IGF-I may not be an adequate biomarker of health during military training.