SUN-LB69 A Comparison Between Weight Loss Associated Bone Loss From Lifestyle Measures Versus Bariatric Surgery

Background Despite improvement in many metabolic outcomes, bone loss remains a concern with weight loss (WL). In this prospective study, we compared the effects of WL from lifestyle intervention (LI) and bariatric surgery (BS) on WL-associated bone loss. We hypothesize that the higher WL from bariatric surgery will result in a greater decline in bone mineral density (BMD) and bone quality. Methods Twenty-nine obese subjects (BMI > 30 kg/m(2); weight: 107±19.3 kg) were included in the study; 13 participated in a LI study of WL (supervised diet+exercise) and 16 underwent BS. Assessments were done at 10% WL and at 6 months. Areal BMD and body composition were evaluated by DXA; bone micro-architecture and bone strength by microfinite element analysis-derived parameters as failure load (f.load) and stiffness at the distal radius and distal tibia were evaluated by high resolution peripheral quantitative computed tomography. Serum bone turnover markers, adipokines and cytokines were measured by Elisa. Results Participants in the LI arm were significantly older (71.3±4 vs 48.2±10 y.o., p < 0.001) and lighter (93.4 ± 8 vs. 118.5±18 kg, P=0.001) compared to the BS arm. Analysis adjusted for baseline age and weight showed no significant differences in areal BMD at all sites, volumetric BMD and bone microarchitectural features of the radius and tibia, except for higher cortical porosity (Ct.Po) at the tibia in the LI arm compared to the BS arm (3.0±0.3 vs 1.7±0.3%, p=0.04, respectively). The average WL at 6 months were -11.87±4.7 vs.-15.96±5.1%, p=0.07, for LI and BS, respectively. At 10%WL, the LI arm had a reduction in trabecular volumetric BMD (tb.vBMD) at the radius (-2.2±1.2 vs. 3.1±4.8% P=0.05) and tibia (-2.2±1.4 vs. 2.2±3.9 % P=0.02, respectively) compared to BS arm which had increases in this parameter. There was also a trend for reduced radius trabecular number and thickness in the LI arm at 10% WL. Meanwhile, there was a trend for reduction in total hip BMD, f.load and stiffness at the radius in the BS arm only. At 6 months, tb.vBMD at the radius was reduced in LI (-2.7±0.9%) relative to the increase in BS group (5.7±2.0%), p=0.008. There was a reduction in F.load (-5.3±2.4 vs 0.6±1.2%, p=0.09) and stiffness (-6.1±2.7 vs. 0.8±1.4%, p=0.08) of borderline significance at the tibia in the BS compared to no change in LI arm. BS arm showed a greater increase in serum C- telopeptide (28.1±48 vs. 81.3±30%, P=<0.05), an index of bone resorption, and in adiponectin (-0.7±8 vs.36.2±22.1%, P=0.01) compared to LI at 6 months. There were no significant differences in changes in lean and fat mass at 6 months in both arms. Conclusion: Although WL from LI resulted in reduced radial tb.vBMD, BS was associated with a greater increase in bone resorption and a trend for reduction in bone strength at the weight-bearing tibia at 6 months compared to LI. Results from this pilot project need confirmation in a larger study with longer duration of follow-up.