Changes in bone mineral density after bariatric surgery in patients of different ages or patients with different postoperative periods: a systematic review and meta-analysis.

To assess changes in bone mineral density (BMD) following bariatric surgery (BS) in patients with different bone sites, postoperative periods and ages. Twenty-two studies were included. Femoral neck (FN) BMD decreased after surgery (MD, - 0.05 g/cm, CI - 0.10 to - 0.01, P = 0.03). Postoperative BMD decreased more in the FN and lumbar spine (LS) of patients older than 40 (FNBMD, - 0.07 g/cm, CI - 0.13 to - 0.00, P = 0.04; LSBMD, - 0.03 g/cm, CI - 0.05 to - 0.00, P = 0.02) or patients with a postoperative time of greater than 12 months (FNBMD, - 0.06 g/cm, CI - 0.12 to - 0.01, P = 0.03; LSMD, - 0.04 g/cm, CI - 0.09 to 0.01, P = 0.12); therefore, post-BS bone loss should be monitored among patients in these groups. Longer follow-ups are needed to determine whether BMD changes or stabilizes.