Bone Abstracts

Objective: In children, factors such as age and puberty are confounders when investigating associations of fat or lean with bone mineral content (BMC). Our aim was to assess influence of fat on BMC in overweight/obese (ow/ob) and normal weight (nw) children at different stages of puberty.

Methods: Cross-sectionally, 244 children+adolescents (6–16 years) (73nw, 177ow/ob) were assessed (tanner staging (TS), body composition (DXA) (total body BMC, lean mass (LBM) and fat (BF))).

Results: BMC was highly correlated with LBM (r=0.68 in boys; r=0.72 in girls, P<0.0001) more so than with BF (r=0.56 in boys, r=0.67 in girls, P<0.0001). After adjustments (age, LBM), ow/ob boys showed higher values of BMC than controls at TS1&2 (910±74 vs 1340±41 g; 1598±39 vs 1358±64 g respectively) (P<0.05); no difference was observed at TS3,4&5; adjusted BMC values in ow/ob girls were significantly higher than controls at all TS’s (P<0.05). Multiple linear regression (entire cohort) was performed at each TS in both genders to assess simultaneous effect of lean, fat on BMC (age adjusted). In boys, at all TS’s, lean was significant predictor of BMC (P<0.001); additionally at TS’s 2, 3, 5 fat was significant predictor (r²=0.71, P<0.01). In girls, at TS’s 1, 2, 3 (r²=0.77) and 5 (r²=0.41) lean was significant predictor (P<0.05); at TS3 fat was also predictor (r²=0.77), at stage 4 (r²=0.53) fat was the only predictor.

Conclusion: Differential relationships between lean, fat and bone were observed in both genders at different TS’s; lean was the main predictor in all children (nw, ow/ob) at almost all TS’s. In boys, at earlier TS’s, bone mass was higher in ow/ob boys, but this effect of fat on bone was not maintained at later TS’s, suggesting that intervention may be necessary at later TS’s to improve bone mass in overweight/obese boys.