Bone resorption following weight loss surgery is associated with treatment procedure and changes in secreted Wnt antagonists

To assess if altered bone turnover following bariatric surgery is related to metabolic consequences of the surgical procedure or weight loss. We evaluated serum markers reflecting bone turnover and metabolic pathways at baseline and after 1-year in a controlled non-randomized clinical trial comparing Roux-en-Y gastric bypass surgery (n = 74) with lifestyle intervention (n = 63) on obesity-related comorbidities. The decrease in body mass index (BMI) was larger in the surgery (−14.0 kg/m²) compared to lifestyle (−3.7 kg/m²). Markedly increased bone turnover was observed following surgery compared to lifestyle intervention and was correlated with change in BMI. Stepwise multivariable regression analysis revealed that group (β = 0.31, p < 0.01), and changes in BMI (β = −0.28, p < 0.01), dickkopf-1 (β = 0.20, p < 0.001) and sclerostin (β = 0.11, p < 0.05) were predictors of change in the bone resorption marker N-terminal telopeptide. Our data support that mechanisms related to the procedure itself and changes in secreted Wnt antagonists may contribute to increased bone turnover following bariatric surgery.