Short- and mid-term changes in bone mineral density after bariatric surgery in obese women (#25)
Bariatric surgery is the most effective treatment to induce significant and sustained weight loss (in morbidly obese subjects. However, there is emerging evidence that bariatric, particularly malabsorptive (Roux-en-Y bypass; RYGB) surgery, may reduce bone mineral density (BMD). Whether such effects differ by procedure or are due to the amount of weight loss per se is unknown. We compared the effects of ~20% weight loss induced by RYGB, sleeve gastrectomy (SG) or gastric band (Band) on lumbar spine and femur BMD in women.
Twenty-two morbidly obese women (BMI=41.8±7.4kg/m2; Age=46.6±12.3y) underwent RYGB (n=6), SG (n=9) or Band (n=7). The groups were similar in age and BMI. Lumbar spine and femur BMD (DXA, Lunar) were measured at baseline, 6 and 18 months. Mixed model analyses were performed to examine the effects of time and surgery group on BMD.
Body weight loss was 33.6±1.7, 34.5±7.3, 18.3±6.3% eighteen months after RYGB, SG and Band, respectively. Mixed modelling analyses revealed a significant effect of time (P=0.006), but not surgery group, on FemurBMD (Baseline=1.10±0.02; 6 months=1.08±0.02; 18 months=1.01±0.03gm/cm2). There were no significant effects of time or surgery group on lumbarBMD. Next, we matched for equivalent weight loss in the 3 surgery groups. Women in the RYGB, SG and Band groups lost 18.1±3.9, 17.4±5.2 and 18.1±5.5% of their body weight by 14±3, 14±3 and 72±4weeks after surgery, respectively. After equivalent weight loss, there were no differences in Lumbar or FemurBMD between the 3 surgery groups.
In conclusion, we observed 9% decreases in femur bone mineral density 18 months after bariatric surgery. Further studies comparing the effects of surgical and non-surgical weight loss interventions on bone density are required.