Influence of segmental body composition and adiposity hormones on resting metabolic rate and substrate utilization in overweight and obese adults.

PURPOSE: Low resting metabolic rate (RMR) and high carbohydrate reliance at rest are associated with weight gain, but are highly variable in obese individuals. This study determined the relationship of total and segmental body composition and adiposity hormones with RMR and respiratory exchange ratio (RER) in overweight and obese adults. METHODS: In 49 men (n = 23) and premenopausal women (n = 26) [mean ± SD; age = 35.0 ± 8.9 years; body mass index (BMI) = 33.6 ± 5.2 kg·m-2; percent body fat (%fat) = 40.0 ± 8.0%], RMR and RER were evaluated using indirect calorimetry. Total and segmental body composition [fat mass (FM), percent fat (%fat), lean mass (LM), visceral adipose tissue (VAT)] were estimated using dual-energy X-ray absorptiometry. Fasted blood and saliva samples were analyzed for insulin, leptin, estradiol, and cortisol. RESULTS: In men (M) and women (W), RMR significantly correlated (p < 0.05) with FM (M: R = 0.535; W: R = 0.784) and LM (M: R = 0.645; W: R = 0.867). Of the segmental measures, trunk LM (M: R = 0.593; W: R = 0.879; p < 0.05) and leg LM (M: R = 0.664; W: R = 0.821; p < 0.05) had the strongest correlations with RMR. In men, but not women, RER significantly correlated with FM (R = 0.449; p = 0.032), trunk FM (R = 0.501; p = 0.015), and VAT (R = 0.456; p = 0.029). In men, RMR positively correlated with cortisol (R = 0.430, p = 0.040) and estradiol (R = 0.649, p = 0.001) and RER positively correlated with insulin (R = 0.525, p = 0.010). In women, RMR positively correlated with insulin (R = 0.570, p = 0.006), but RER was not significantly correlated with hormones (p > 0.05). CONCLUSIONS: Segmental evaluation of body composition, specifically in the lower extremities and abdomen, may be an effective and efficient way to evaluate metabolic status. Sex-specific evaluations are also imperative.

Body Composition, Muscle Quality and Scoliosis in Female Collegiate Gymnasts: A Pilot Study.

Research has demonstrated an elevated prevalence of body weight concerns and scoliosis among female gymnasts. The purpose of the current pilot study was to evaluate the utility of ultrasonography and dual-energy X-ray absorptiometry (DXA) as practical imaging modalities to measure body composition and spinal curvature variables that may correlate with performance in female collegiate gymnasts (n=15). DXA was used to evaluate body composition and lateral spinal curvature, utilizing a modified Ferguson method. Echo intensity (EI) and cross-sectional area (CSA) of the vastus lateralis were determined from a panoramic cross-sectional ultrasound image. For returning athletes (n=9), performance scores from the previous season were averaged to quantify performance. The average performance score was correlated with lean mass of the arms (R=0.714; P=0.03) and right leg (R=0.680; P=0.04). Performance was not correlated with total mass, fat mass or body fat percentage (P>0.10). Scoliosis was identified in 3 of 15 scans (20%). Echo intensity and CSA of the vastus lateralis were inversely correlated with each other (R=-0.637, P=0.01), but not with other measures of body composition or performance. Results suggest that limb LBM may be a determinant of gymnastics performance, and DXA may provide important health and performance-related information for female collegiate gymnasts.