The Impact of Fat and Obesity on Bone Microarchitecture and Strength in Children

Joshua N. Farr, Paul Dimitri

A complex interplay of genetic, environmental, hormonal, and behavioral factors affect skeletal development, several of which are associated with childhood fractures. Given the rise in obesity worldwide, it is of particular concern that excess fat accumulation during childhood appears to be a risk factor for fractures. Plausible explanations for this higher fracture risk include a greater propensity for falls, greater force generation upon fall impact, unhealthy lifestyle habits, and excessive adipose tissue that may have direct or indirect detrimental effects on skeletal development. To date, there remains little resolution or agreement about the impact of obesity and adiposity on skeletal development as well as the mechanisms underpinning these changes. Limitations of imaging modalities, short duration of follow-up in longitudinal studies, and differences among cohorts examined may all contribute to conflicting results. Nonetheless, a linear relationship between increasing adiposity and skeletal development seems unlikely. Fat mass may confer advantages to the developing cortical and trabecular bone compartments, provided that gains in fat mass are not excessive. However, when fat mass accumulation reaches excessive levels, unfavorable metabolic changes may impede skeletal development. Mechanisms underpinning these changes may relate to changes in the hormonal milieu, with adipokines potentially playing a central role, but again findings have been confounding. Changes in the relationship between fat and bone also appear to be age and sex dependent. Clearly, more work is needed to better understand the controversial impact of fat and obesity on skeletal development and fracture risk during childhood.