Soft Tissue Composition, Cardiometabolic Risk, and Bone Development in Young Girls

Abstract

Obesity in childhood is a major pediatric concern as excess adiposity increases the risk for developing metabolic dysfunction, cardiovascular disease (CVD) and type 2 diabetes in adulthood. Far less attention has been focused on the effects of obesity during childhood on bone development. Obesity and skeletal fragility have been previously thought to be two distinct conditions rarely found occurring in the same individual, as excess adiposity is thought to enhance bone strength due to the increase in mechanical loading on the skeleton stimulating bone formation. In fact, overweight and obese children tend to have larger bones and greater bone mineral content and density than children with healthy weight. On the contrary, there have been recent findings of a greater fracture incidence in obese children compared to those of normal weight. Overall, the relationship between excess adiposity and bone remains controversial, with reports of both augmented and compromised bone mass accrual in overweight and obese children. There is evidence that obesity-related metabolic dysfunction may compromise gains in bone mass, despite the increased loading on bone with excess weight. Thus, the conflicting relationship reported between excess adiposity and bone in children may be explained by the presence of metabolic dysfunction in some but not all overweight and obese children. The objective of this dissertation was to use cross-sectional data from the “Soft tissue and bone development in young girls (STAR)” study to examine the relationship of soft tissue composition with measures of bone density, geometry, and strength in young girls and assess the influence of cardiometabolic risk factors, which are biomarkers of metabolic dysfunction, on these relationships. Through utilizing state-of-the-art, direct imaging techniques to measure body composition and parameters of bone density, geometry, and strength, findings from this study showed that fat mass is a positive contributor to bone independent of lean mass, however the degree to which adiposity adds to total bone mass and area may be attenuated if there is co-occurring metabolic dysfunction. These findings indicate that obesity in children is a protective factor for bone, however, the attenuation of this protective effect due to the presence of metabolic dysfunction may compromise maximum bone mineral accrual in obese children during a time when maximizing bone mineral accrual is of utmost importance for fracture and osteoporosis prevention in adulthood. Hence, obesity in children should not only be seen as a risk factor for cardiovascular disease, but should be recognized as a risk factor for compromised bone development.