Sarno, GerardoGerardoSarnoSIMANCAS RACINES, DANIEL ALEJANDRODANIEL ALEJANDROSIMANCAS RACINESGargiulo, AntonioAntonioGargiuloAnna TedescoIacone, BiancamariaBiancamariaIaconeClaudia Reytor-GonzálezParise Vasco Juan MarcosJaime Angamarca IguagoSarno, SabrinaSabrinaSarnoFrias-toral EvelynBracale, UmbertoUmbertoBracale2025-07-182025-07-182025-08https://doi.org/10.1016/j.semcancer.2025.05.012Background Obesity has been increasingly recognized as a factor that influences postoperative outcomes in colorectal cancer surgery. However, its impact on surgical complications, mortality, and oncological outcomes remains controversial. This systematic review and meta-analysis aimed to evaluate the association between obesity and postoperative complications in colorectal cancer surgery. Methods A comprehensive search was conducted in MEDLINE/PubMed, Scopus, and Embase, including studies evaluating body mass index (BMI) in relation to postoperative complications such as infections, anastomotic leakage, postoperative ileus, bleeding, reoperation, and mortality. Data synthesis involved a qualitative analysis of all eligible studies and a meta-analysis when applicable. The quality of the studies included was assessed using the Newcastle-Ottawa Scale, while the certainty of evidence was evaluated through the Grading of Recommendations, Assessment, Development and Evaluations (GRADE) approach. Results Twenty-nine studies were included in the qualitative analysis and 17 were eligible for the meta-analysis. Compared to BMI < 30 kg/m², patients with BMI ≥ 30 kg/m² showed significantly higher risk of any type of surgical site infection (OR=1.49; 95 % CI: 1.37–1.70; low certainty). No significant differences were found in mortality (OR=1.23; 95 % CI: 0.72–2.11; very low certainty), hemorrhage (OR=1.05; 95 % CI: 0.97–1.14; very low certainty), or gastrointestinal complications (OR=1.10; 95 % CI: 0.96–1.26; very low certainty). Conclusion Obesity significantly increases the risk of surgical site infections in colorectal cancer surgery. Although its impact on mortality and gastrointestinal complications remains unclear, implementing preoperative optimization protocols specifically aimed at obesity management could mitigate these surgical risks. The certainty of evidence ranges from low to very low, highlighting the need for high-quality prospective studies with standardized BMI criteria and surgical protocols.journal-article