Intentional weight reduction before surgery - A systematic review

Obesity may increase complexity of surgical procedures and increase the risk of perioperative complications. Weight reduction by the use of low energy diet (LED, ≤1200 kcal/day) or very low energy diet (VLED, ≤800 kcal/day) can reduce postoperative complications after bariatric surgery, but for most other types of surgery the evidence for its use remains uncertain. The aim of this systematic review was therefore to evaluate the scientific evidence in general for this routine.

The Medline, Embase, Web of Science and Cochrane databases were searched up until November 20, 2024 using the Cochrane risk of bias assessment tool for observational studies and the NIH quality assessment of controlled intervention studies for randomized trials. Operation time, surgeon's perceived difficulty, intraoperative complications, postoperative complications and relevant efficacy measures for specific procedures were considered as endpoints. A random-effects model was used to pool effect sizes for the main analyses.

A total of 7053 studies were identified. After screening by title and abstract, followed by full text, 18 studies (9 RCTs and 9 observational studies) remained for the analyses including 854 patients who received the intervention and 979 controls. Preoperative LED/VLED resulted in an overall shorter operation time (standard mean difference 0.36, 95 % CI 0.14-0.59, p = 0.002), and reduced risk of postoperative complications after bariatric surgery, cholecystectomy, colorectal surgery and hernia repair (pooled RR 0.63, 95%CI 0.51-0.79, p < 0.001). Heterogeneity between studies was high for operation time but very low for complications. No difference was seen for intraoperative complications, while the data did not allow further analyses on perceived difficulty of surgery or efficacy outcomes.

The results support the use of LED/VLED for short-term preoperative weight reduction in patients with obesity planned for bariatric surgery and for those undergoing cholecystectomy, colorectal surgery and hernia repair. Further studies including a comparable control group are needed to evaluate its routine use for other surgical procedures.

The protocol of this study was preregistered at the International Prospective Register of Systematic Reviews, PROSPERO.