Effects of Weight Loss Surgery on Bone Health in Adolescents

The purpose of this study is to examine the impact of weight-loss surgery (Roux-en-Y gastric bypass or Vertical Sleeve Gastrectomy) on bone outcomes in girls and boys ages 13-21. This study will also examine a group of overweight boys and girls who are not scheduled or planned for surgery for comparison of these outcomes. Obese adults who undergo weight-loss surgery are at risk for bone loss and decreased bone strength. The investigators do not know the effects of such surgery on bone in teenagers and young adults. The purpose of this study is to find out how different types of weight loss surgery affect bone density and strength in teenagers and young adults and compare these results to obese teenagers and young adults who are not undergoing weight-loss surgery.

Our overall hypothesis is that both Roux-en-Y Gastric Bypass (RYGB) and vertical sleeve gastrectomy (VSG) in adolescents with morbid obesity will lead to a reduction in areal and volumetric BMD, and deterioration in bone structure and estimated bone strength, and an increase in marrow adiposity. We further hypothesize that these effects will be due in part to a decrease in lean mass, changes in enteric peptide hormones and reduced estrogen levels. We will enroll 120 participants 13-21 years old for this two-year longitudinal study (36 in each of the surgical groups and 48 non-surgical controls with obesity). We will screen up to 240 subjects to find these 120 eligibile subjects. Areal bone mineral density (BMD) will be assessed by dual energy x-ray absorptiometry (DXA), volumetric BMD by quantitative computed tomography (QCT), bone structure and strength using high resolution peripheral QCT and finite element analysis, and marrow fat using magnetic resonance spectroscopy. Body composition will also be assessed. Adolescence is a critical time for bone accrual and the use of bariatric procedures is increasing in teenagers. This study will provide novel data needed to establish effects of RYGB vs. VSG on bone in adolescents and will begin to delineate underlying mechanisms. Clarifying these mechanisms will identify therapeutic targets to optimize bone accrual in adolescents undergoing bariatric surgery.