Bariatric surgery for severe obesity results in a rapid weight loss and beneficial metabolic effects, but may have negative effects on the skeleton. We evaluated the changes in bone turnover in response to bariatric surgery with two surgical techniques, Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG). Forty-six morbidly obese subjects (mean age 44.9 yrs, BMI 42.1) were operated with RYGB (n=21) or SG (n=25). Twenty-five healthy subjects with normal body weight (mean age 45.8 yrs, BMI 23.0) were recruited as controls. Fasting serum samples were collected before and 6 months after the operation and bone turnover markers (CTX, PINP, TRAcP5b, osteocalcin) were analysed. Volumetric bone mineral density (vBMD) was measured by quantitative computed tomography in a subset of 21 subjects. Both RYGB and SG resulted in a significant weight loss and decrease in fasting plasma glucose and insulin (p<0.001 for all). At baseline, obese subjects had significantly lower levels of bone markers than the healthy subjects (p<0.05). Levels of bone markers increased significantly 6 months after surgery (p<0.001 for all). The median increases in CTX, PINP, TRAcP5b and osteocalcin were greater (p<0.01) after RYGB (303, 162, 72 and 141%, respectively) than after SG (106, 59, 27 and 60%). In the subset with vBMD analysis, vertebral vBMD increased in obese subjects without DM2 (N=13) (p=0.055), while there was no change in obese subjects with DM2 (N=8). Bone markers increased in all obese subjects irrespective of their DM2 status (p<0.05 for all). The surgical method did not affect the change in vBMD (p=0.60). Bone turnover is increased in response to bariatric surgery but is affected by the surgical technique. In contrary to previously published data on areal BMD by DXA, vBMD does not decrease, but may even increase at short term, in non-diabetic patients after bariatric surgery.
Disclosure: The authors declared no competing interests. This study was supported by grants from the Academy of Finland, Sigrid Juselius Foundation and Turku University Hospital Research Funds.