To evaluate systematically whether Preoperative weight loss can improve the clinical efficacy of patients undergoing bariatric surgery.

The study was collected by searching the database of PubMed, Emabase and Cochrane. The retrieval time was from inception of the database to October 2020. Meta-analysis was performed with Review Manager 5.3. The improvement of preoperative complications, conversion to endoscopy, operation time, hospital stay, unplanned secondary operation, postoperative wound infection, postoperative bleeding, early postoperative complications, improvement of postoperative complications and postoperative weight loss were evaluated.

A total of 10 studies were finally included involving 6000 patients. Meta-analysis showed that, compared with the routine control group, reduced weight before operation group had no benefit in preoperative complications improvement, intraoperative endoscopic conversion, operation time, early postoperative complications, and postoperative bleeding, postoperative wound infection, unplanned second operation, hospital stay, postoperative complications improvement, weight loss index after 6 months, weight loss index after 12 months. There was no significant difference between the two groups. But, the weight loss before operation was more obvious within 3 months after operation.

Preoperative weight loss before bariatric surgery may make patients lose weight more obviously in the short term after operation, but they cannot benefit from perioperative risk, improvement of complications, hospital stay, and long-term weight loss and so on. Its clinical effect still needs the help and support of more high-level evidence-based research evidence.