Bone Abstracts

Objective: This work investigated the changes of bone hip structural parameters in obese adolescents enrolled in a successful weight loss program.

Methods: Thirty-one obese adolescents (age 13.61±1.27) enrolled in a 8-month weight loss program combining physical activity and nutrition were compared with normal-weight (NW) matched peers (age 15.9±0.43). Investigations were performed at baseline and 8 months. Bone geometric and strength indices were quantified by DXA using hip structural analysis at the narrow neck (NN) and femoral shaft (FS).

Results: At the end of the interventional program, obese adolescents had geometric bone indices significantly lower than controls at NN for endocortical diameter (ED) (P=0.005) and width (P=0.003). At FS bone density (P=0.004), ED (P=0.006) and cortical thickness (CT) (P=0.001) were significantly reduced compared with normal peers. Also, compared with unchanged loading (NW), reduced load (obese from the intervention group) significantly increased axial strength (cross sectional area (CSA); section modulus (Z)) at NN and FS and bending strength (cross sectional moment of inertia (CSMI)) at FS leading to similar raw data compared with NW. However, at the end of the intervention obese adolescents had higher bulking ratio at NN (8.25±2.00 vs 6.92±1.0; P=0.008) and at the shaft (2.73±0.54 vs 2.27±0.47; P=0.004). After adjusting for body weight changes, bone density (NN P=0.007; FS P<0.001) and CT (NN P=0.05; FS P=0.009) became significantly lower in the obese population. Also, obese adolescents displayed lower bending and torsional (CSMI P<0.001; Z P<0.001) strength, lower resistance to axial stresses (CSA P<0.001; Z P<0.001) at both sites but higher bulking ratio (P=0.027) at NN only. Finally, after adjustment for fat mass changes, lower bone density (P=0.003) and CT (P=0.011), higher ED (P=0.018) and bulking ratio (2.87 (95%CI 2.396–2.961) vs 2.32 (2.035–2.600) P=0.004) were observed at the shaft in obese adolescents.

Conclusion: The present results suggest that, after a weight loss, geometric indices of bone strength at weight bearing site remain unadapted to excess body weight despite positive adaptation of bone parameters. Moreover, reduced load appeared to cause higher fragility at the NN than at the shaft.

Conflict of interest: Nothing to declare.

Disclosure: The authors declared no competing interests.