Randomized Controlled Trials of Weight Loss Before Hernia Surgery: A Systematic Review and Meta-Analysis

Hernia repairs are one of the commonest operations performed in the world. In Europe and the United States of America more than half of patients undergoing hernia surgery are overweight or obese; body weight is therefore key modifiable risk factor before surgery. We aimed to identify, appraise, and synthesise the randomized controlled trial (RCT) evidence for any weight loss interventions before any form of hernia surgery.

A search was performed in April 2025 of the PubMed, EMBASE and CENTRAL databases. Meta-analysis was performed using random effects to assess mean difference in weight, and fixed effects for odds ratio of complications. Bias was assessed using the Cochrane Rob2 tool. Certainty effect was assessed using GRADE methodology. This review was registered with PROSPERO (ID 1024784).

1,707 studies were screened, 20 retrieved, and 4 reports of 3 RCTs included. A total population of 219 patients largely underwent ventral hernia repair, although 2 RCTs also included patients undergoing non-hernia surgery. Interventions comprised very low calorie diets (VLCD), and a multidisciplinary programme. Meta-analysis for VLCD did not show a reduction in weight loss (3.64 kg [95% confidence interval -2.07 - 9.35]) or complications [odds ratio 0.36 (0.1-1.28)]. Risk of bias was "high," and certainty of effect "very low."

Despite the prevalence and importance of obesity in patients undergoing elective hernia repair, and the popularity of weight loss as part of prehabilitation, the randomized evidence of how to effect weight loss, and whether this translates into an improvement in clinical outcomes is minimal. This highlights the urgent need for large and robust RCTs to determine if weight loss before hernia repair is effective in improving outcomes for patients, and how this is best achieved.