Total body, lumbar spine and hip bone mineral density in overweight adolescent girls: decreased or increased?

Despite the epidemic of overweight adolescents, the effect of being overweight on bone mineral density (BMD) during this period is poorly understood. However, recent studies have suggested that overweight adolescents have lower BMD compared to normal-weighted adolescents after adjusting for body weight. The aim of this study was to determine the influence of being overweight on bone status in a group of adolescent girls. This study included 22 overweight (BMI >25 kg/m²) adolescent girls (15.4 ± 2.4 years old) and 20 maturation-matched (15.2 ± 1.9 years old) controls (BMI <25 kg/m²). Bone mineral area, bone mineral content, BMD at the whole body (WB), lumbar spine (L2–L4), femoral neck (FN), total hip (TH) and body composition (lean mass and fat mass) were assessed by dual-energy X-ray absorptiometry (DXA). Calculation of the bone mineral apparent density (BMAD) was completed for the WB and for L2–L4. Expressed as crude values, DXA measurements of BMD at all bone sites (TB, L2–L4, TH and FN) were higher in overweight adolescent girls compared to controls. After adjusting for either body weight, lean mass or fat mass, these differences disappeared. Finally, BMAD of the L2–L4 remained higher in overweight girls compared to controls after adjusting for lean mass. We conclude that overweight adolescent girls do not have lower BMD when compared with controls, even when BMD values are adjusted for weight, lean mass or fat mass.