PREDICTORS OF BODY COMPOSITION AND BODY ENERGY CHANGES IN RESPONSE TO CHRONIC OVERFEEDING

OBJECTIVE: We have previously shown that 24 young lean men (12 pairs of identical twins) subjected to a standardized 353 MJ (84 000 kcal) overfeeding protocol over 100 days exhibited individual differences in body weight and composition gains. The mean (+SD) gains in fat mass (FM) and fat-free mass (FFM) were 5.4+1.9 kg and 2.7+1.5 kg for a total body energy (BE) gain of 221+75 MJ representing 63% of the energy surplus consumed. We report here on the most important baseline correlates of these overfeeding-induced changes with the aim of identifying biomarkers of the response. RESULTS: Baseline maximal oxygen uptake per kilogram body mass was negatively correlated with gains in weight, FM, and BE (all p<0.05). Enzyme activities indicative of skeletal muscle oxidative potential correlated with gains in FM and BE (all p<0.05). Baseline TSH levels in response to a TRH stimulation correlated positively with changes in FM-to-FFM ratio (p<0.05). Plasma concentrations of androstenediol-sulfate, dehydroepiandrosterone, and 17-hydroxy pregnenolone were negatively correlated with gains in FM and BE (0.01<p<0.05), while level of estrone was negatively and androsterone-glucoronide was positively correlated with FFM gains (p<0.05). Baseline leptin and abdominal fat cell size correlated positively with gains in weight, FM, and BE (p<0.05). When compared to the six highest BE gainers, the six lowest gainers exhibited higher thermic effect of a meal (TEM) and plasma levels of total testosterone, cortisol, estradiol, androstenedione, and androstenediol-sulfate (all p<0.05). High baseline levels of total TEM, testosterone, and androstenediol-sulfate were associated with lower FM gains whereas high baseline levels of FT4 and estrone were found in low-FFM gainers. CONCLUSION: Although none of the variables exerted individually an overwhelmingly strong influence on overfeeding-induced changes, baseline FFM, maximal oxygen uptake, muscle oxidative capacity, androgens, and leptin levels were the most consistent significant biomarkers of the responsiveness to chronic overfeeding.