Obesity, bariatric surgery, and bone strength: a review and studies in adult cohorts.

Abstract

Bone mass and strength changes proceeding weight loss in obese individuals are important for determining risk for skeletal fragility. Understanding the relationship between obesity and bone strength is significant for describing bone's response to changes in body composition. The three manuscripts presented in this dissertation focus on obese adult populations (aged 18 - 64 years). Peripheral quantitative computed tomography (pQCT) was used to assess volumetric bone mineral density, bone geometry, indices of bone strength, and muscle cross-sectional area. Manuscript I reviews the association between bariatric surgery, changes in bone mineral density, and osteoporosis. The review demonstrated significant loss of bone density at hip and spine sites in the first year following bariatric procedures. However, existing research fails to support the concern over risk of osteoporosis in these individuals. Manuscript II of this dissertation, a cross-sectional study, demonstrated that despite greater absolute bone strength observed in obese women compared to their healthy-weight counterparts, bone strength was low relative to their high body weight. Manuscript III was a prospective observational pilot study to examine changes in bone strength and body composition in morbidly obese adults submitted for bariatric surgery. The results showed that bariatric surgery produced significant weight loss that was predominately due to reduction in fat mass, rather that fat-free mass. Despite significant weight loss bone strength indices were not compromised, suggesting that maintenance of lean mass may preserve bone strength. This dissertation contributes to the knowledge base in several ways. First, it provides a comprehensive summary of bariatric surgery and bone density research, while providing an alternative perspective for interpreting dual x-ray absorptiometry-based bone outcomes. Second, bone strength was assessed using pQCT, which provides an understanding of bone from a mechanical perspective that has not been used when interpreting bone outcomes in severely obese populations. Finally, this dissertation includes the first known study to examine changes in bone strength following bariatric surgery in morbidly obese individuals.