Gender differences in bone mineral density in obese children during pubertal development

Objective: To investigate whether body mass index (BMI) and body composition can affect peak bone mass in a population of obese (OB) (BMI SDS>2.0) and normal-weight (NORM) (BMI-SD score <2.0) pubertal subjects (Tanner stage T3 to T5). Patients and methods: 151 subjects (81 OB, age14.5±2.4 yr) were analyzed using dual-X-ray absorbiometry technique to study Lumbar and whole body bone mineral density (BMD) (areal, normalized for height) and Z-score, lean mass (LM) and lean/fat ratio. Results: As a whole group, OB males did not show any significant difference in bone parameters vs NORM, while OB females showed higher bone density parameters (p<0.05). When grouped according to T, while OB males showed higher bone density at T3-4 stage (p<0.01 ), and lower at T5 (p<0.01 ) compared to NORM, OB females showed a tendency through increased BMD at T3–4 and T5 although statistically different only at T5. BMD was independently correlated to LM, lean/fat ratio, and testosterone in NORM males and, at lower level, in OB males, while to LM in NORM females and only to age in OB females. Conclusion: Our data seem to confirm the possible negative influence of obesity on bone density in boys, a possible explanation could be an unfavorable body composition during sexual maturation that seems not to affect bone development in adolescents girls.