Objective: To systematically evaluate the efficacy and safety of GLP-1 receptor agonists applied at different stages before and after bariatric surgery, and to compare the clinical benefits of preoperative use, early postoperative use, and rescue use after insufficient weight loss or weight regain according to medication timing. Methods: PubMed, Web of Science, and Embase via Ovid were searched from inception to June 20, 2026. A relatively strict three-concept search strategy was used, consisting of terms related to bariatric surgery, GLP-1 receptor agonists and specific drug names, and perioperative or weight-management scenarios. Searches were mainly restricted to title and abstract fields, and animal-only studies were excluded. Clinical studies involving patients who underwent metabolic and bariatric surgery and received GLP-1 receptor agonists before or after surgery were included. Studies were classified into three groups according to medication timing: preoperative use, early postoperative use, and rescue use after insufficient weight loss or weight regain. Mean difference or standardized mean difference was used for continuous variables, and odds ratio was used for categorical variables. Meta-analysis was performed using a random-effects model. Results: A total of 27 studies were included in the systematic review, including 10 studies on preoperative use, 4 on early postoperative use, and 13 on rescue use after insufficient weight loss or weight regain. Among them, 13 studies were included in efficacy meta-analyses. Preoperative use of GLP-1 receptor agonists improved preoperative weight loss, with a pooled SMD of 0.52 (95%CI: 0.25-0.79, I²=0%, P<0.05). However, when postoperative weight loss at 12 months was assessed using body weight at surgery as the baseline, the percentage of total body weight loss at 12 months was 2.85 percentage points lower in the preoperative medication group than in the non-medication group (95%CI: -4.35 to -1.36, I²=37.7%, P<0.05). Active addition of GLP-1 receptor agonists around 1 month after surgery increased the percentage of total body weight loss at 6 months by an additional 3.62 percentage points (95%CI: 1.88-5.37, I²=0%, P<0.05). Initiation of GLP-1 receptor agonists around 6 months after surgery resulted in an additional weight loss of 7.48 kg during subsequent follow-up compared with controls (95%CI: 5.35-9.60, I²=34.6%, P<0.05). For rescue therapy, four randomized controlled trials showed that GLP-1 receptor agonists resulted in an additional 10.30 percentage points of endpoint percentage weight loss compared with placebo or usual care (95%CI: 6.40-14.20, I²=89.2%, P<0.05). Regarding safety, among studies that clearly reported event numbers, the pooled incidences of nausea, constipation, diarrhea, and vomiting were 25.3%, 19.0%, 9.2%, and 8.6%, respectively. Serious adverse events were uncommon. Conclusion: GLP-1 receptor agonists have timing-specific value in the comprehensive management of metabolic and bariatric surgery. Preoperative use can increase preoperative weight loss but does not enhance postoperative weight loss when body weight at surgery is used as the baseline. Early postoperative use may further amplify weight-loss benefits within the first postoperative year. Rescue use after insufficient weight loss or weight regain is supported by the strongest evidence. In terms of safety, adverse events are mainly gastrointestinal, and serious adverse events are uncommon.
