Bone Abstracts

Child and adolescent obesity has reached epidemic proportions worldwide. The impact of excess fat on musculoskeletal health is of significant concern. Abnormal mechanical loading of the lower limbs in obese children may lead to anatomic alterations and an increased prevalence of slipped capital femoral epiphysis and tibia vara. Obese children are also over-represented in fracture groups and excess fat may result in low bone mass relative to body size, although this effect may be confined to adolescence. Paradoxically, obese adults have a higher bone mass and fracture less, although this observation may be bone site-specific. The factors underpinning this paradox are poorly understood. Changes in bone microarchitecture may differ in relation to the relative proportion of subcutaneous and visceral fat. Fat-induced alterations in hormonal factors and cytokines during growth and pubertal development may play a pivotal role in disturbing osteoblast and osteoclast function and thus bone accrual. These changes may be more prevalent in obese children who have obesity-related metabolic risk factors. Reduced levels of physical activity and calcium intake during childhood and adolescence may further exacerbate poor bone mass accrual in obesity.

Despite a considerable body of bone densitometry data there remains controversy about the affect of obesity in children and adults. DXA is unable to capture changes in bone compartments and adjustments are required during DXA analysis to account for body size in children. Longitudinal analysis using novel scanning techniques including high resolution peripheral quantitative computed tomography (HRpQCT) and skeletal MRI may help to overcome the limitations in using DXA and provide information about obesity-mediated alterations in skeletal microstructure, geometry and strength during growth. Understanding the effects of fat mass on skeletal health during growth is vital in informing future health strategies to optimise peak bone mass and prevent fracture across all ages.