# Intentional Preoperative Weight Loss for Obesity in Patients Undergoing Gastrointestinal Cancer Resections: A Systematic Review and Meta-analysis

## TL;DR

Intentional preoperative weight loss in obese patients undergoing GI cancer surgery is feasible, safe, and may reduce postoperative complications.

## Contribution

Demonstrates that structured preoperative weight loss in obese GI cancer patients is safe and reduces surgical complications.

## Key findings

- Preoperative weight loss was completed by 96.9% of participants without harms or delays.
- Weight loss reduced overall postoperative complications and anastomotic leak rates significantly.
- Skeletal muscle mass and nutritional parameters were preserved in the intervention group.

## Abstract

Obesity is increasingly prevalent in patients undergoing gastrointestinal (GI) cancer surgery and is associated with higher rates of intraoperative and postoperative complications. Preoperative weight loss has been proposed as a potential strategy to optimise surgical outcomes, but evidence regarding its safety, efficacy, and feasibility remains unclear.

A systematic search was conducted across MEDLINE, PubMed, EMBASE, and Cochrane from inception to 28th May 2025, following PRISMA 2020 guidelines and a registered protocol (PROSPERO ID: CRD42020154074). Eligible studies included adults (≥ 18 years) with obesity (BMI ≥ 30 kg/m²) undergoing surgery for GI cancers who received a structured preoperative weight loss intervention. Primary outcomes were feasibility and overall postoperative complication rates. Secondary outcomes included anastomotic leak, operative time, and adverse events. Meta-analysis was performed per outcome measure.

Eight observational cohort studies comprising 532 patients (213 weight loss intervention vs. 319 control) were included. Completion rates for preoperative weight loss were ≥ 96.9%, with no intervention-related harms or surgical delays reported. Pooled analysis demonstrated a significant reduction in overall postoperative complications (OR 0.37, 95% CI 0.16–0.85; p = 0.02) and anastomotic leak (OR 0.26, 95% CI 0.12–0.60; p = 0.002) in the intervention group. Where assessed, skeletal muscle mass and nutritional parameters were preserved.

Intentional preoperative weight loss appears feasible, safe, and may improve postoperative outcomes in patients with obesity undergoing GI cancer surgery. Integration of such strategies, particularly during neoadjuvant therapy windows, offers a modifiable opportunity to optimise surgical risk. Prospective trials are warranted to define optimal protocols, timing, and oncologic safety.

The online version contains supplementary material available at 10.1007/s12029-026-01405-1.