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 (+s.d.) 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 kg 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 thyroid-stimulating hormone levels in response to thyrotropin-releasing hormone 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 <0.05), whereas the level of estrone was negatively correlated and androsterone glucoronide was positively correlated with FFM gains (Po0.05). Baseline leptin and abdominal fat cell size correlated positively with gains in weight, FM and BE (P<0.05). When compared with 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.