Short- and mid-term changes in bone mineral density after bariatric surgery in obese women — ASN Events

Short- and mid-term changes in bone mineral density after bariatric surgery in obese women (#25)

Charmaine Tam 1 2 , Georgia Rigas 3 , Tania Matisan 3 , Michael Talbot 3
  1. Charles Perkins Centre and School of Biological Sciences, The University of Sydney, Sydney, NSW, Australia
  2. The Boden Institute of Obesity, Nutrition, Exercise and Eating Disorders, The University of Sydney, Sydney, NSW, Australia
  3. Department of Surgery, St George Hospital Upper GI Unit, Kogarah, NSW, Australia

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.