Long-Term Differential Effects of Gastric Bypass and Sleeve Gastrectomy on Bone Mineral Density

The association of obesity with bone fragility fractures is complex and non-linear. Despite good efficacy on weight loss, bariatric surgery (BS) is also associated with bone loss. However, we lack information on risk factors of the long-term deleterious effects of BS on the skeleton.

We aimed to assess the factors associated with low bone mineral density (BMD) performed a long time after Roux-en-Y gastric bypass (RYGB) or sleeve gastrectomy (SG).

This cross-sectional study involved patients at a long distance from their BS that underwent dual-energy x-ray absorptiometry (DXA) with biological factors (vitamins, micronutrients, bone and inflammation biomarkers). Simple and multiple linear models (stepwise and parsimony approach) were developed.

A total of 131 patients (91 RYGB, 40 SG) underwent DXA (51.8 ± 11.08 years, 87.8% women). At a mean of 6.8 ± 3.7 years after surgery, the mean weight loss was -28.6 ± 9.6%, and only 6 patients (5.7%) had a T-score less than or equal to -2.5. On univariate analysis, BMD was lower in the RYGB than in the SG group (P < .001) at all sites, despite similar fat and fat-free mass and weight loss. Serum parathyroid hormone and phosphate levels were higher in RYGB than SG patients. A total of 10.1% of patients showed vascular calcifications. On multivariable analysis, BMD remained different between surgery groups after adjustment for age, body mass index, ethnicity, and sex. The model-adjusted R ² values were 0.451 for the total hip; 0.462 the femoral neck, and 0.191 the lumbar spine for the inflammation model; 0.458, 0.462, and 0.254, respectively, for the bone marker model; and 0.372, 0.396, and 0.142 for the vitamin model. Serum zinc, ferritin, and uric acid levels were the markers associated with BMD to a low extent.

BMD differed depending on the BS procedure. A few biological markers may be associated weakly with BMD well after the surgery.