Gastric Bypass Surgery for Morbid Obesity Leads to an Increase in Bone Turnover and a Decrease in Bone Mass

TLDR

Little is known about how laparoscopic Roux‑en‑Y gastric bypass for morbid obesity affects the skeleton. The study calls for longer‑term research to evaluate these skeletal effects. The authors compared 25 post‑LRGB patients with 30 matched obese controls and followed 15 patients prospectively for up to nine months after surgery. Within 3–9 months after LRGB, patients exhibit significant weight loss, markedly elevated bone turnover markers, and reductions in bone mineral density at the hip, trochanter, and whole body, indicating increased bone resorption and loss of bone mass.

Abstract

Abstract Little is known about the effects on the skeleton of laparoscopic Roux-en-Y gastric bypass (LRGB) surgery for morbid obesity and subsequent weight loss. We compared 25 patients who had undergone LRGB 11 ± 3 months previously with 30 obese controls matched for age, gender, and menopausal status. Compared with obese controls, patients post LRGB had significantly lower weight (92 ± 16 vs. 133 ± 20 kg; P < 0.001) and body mass index (31 ± 5 vs. 48 ± 7 kg/m2; P < 0.001). Markers of bone turnover were significantly elevated in patients post LRGB compared with controls (urinary N-telopeptide cross-linked collagen type 1, 93 ± 38 vs. 24 ± 11 nmol bone collagen equivalents per mmol creatinine; and osteocalcin, 11.6 ± 3.4 vs. 7.6 ± 3.6 ng/ml; both P < 0.001). Fifteen patients were studied prospectively for an average of 9 months after LRGB. They lost 37 ± 9 kg and had a 29 ± 8% fall in body mass index (both P < 0.001). Urinary N-telopeptide cross-linked collagen type 1 increased by 174 ± 168% at 3 months (P < 0.01) and 319 ± 187% at 9 months (P < 0.01). Bone mineral density decreased significantly at the total hip (7.8 ± 4.8%; P < 0.001), trochanter (9.3 ± 5.7%; P < 0.001), and total body (1.6 ± 2.0%; P < 0.05), with significant decreases in bone mineral content at these sites. In summary, within 3 to 9 months after LRGB, morbidly obese patients have an increase in bone resorption associated with a decrease in bone mass. Additional studies are needed to examine these findings over the longer term.