Correlations among whole-body fat, bone, and biomarkers in boys and girls with obesity: a cross-sectional study.

PURPOSE This study aimed to investigate correlations among body composition, bone parameters, and biomarkers in boys and girls with excess body fat percentage (%fat).

METHODS Healthy boys and girls aged 13-14 years with >95th percentile %fat for age and sex were included. Body composition and bone parameters of the whole body (WB) were measured using dual-energy x-ray absorptiometry. Serum biomarkers were measured via enzyme-linked immunosorbent assay. Comparisons of these parameters between sexes were analyzed using bivariate and multivariate correlation analyses.

RESULTS Boys and girls had no differences in %fat or body fat mass (BFM), but boys had more lean body mass (LBM) than girls. %Fat and BFM were key negative predictors of %bone in both sexes, while serum parathyroid hormone (PTH) and C-terminal cross-linking telopeptide (CTX) were predictors of %bone in girls. Both PTH and CTX were correlated with %bone in boys. Serum leptin was a predictive factor of %bone in both sexes. In addition, %bone was strongly correlated with bone mineral density (BMD) z-score and BMD z-score of participants was negatively correlated with %fat and BFM. In girls, %fat, PTH, and leptin were predictors of BMD z-score. Furthermore, BFM in girls and both BFM and LBM in boys were positively correlated with WB bone mineral content.

CONCLUSION Excess %fat has a deleterious effect on WB bone in both boys and girls, potentially due to bone resorption. BFM may have a protective effect on bone through a mechanical loading mechanism.