From overweight/obesity to metabolic syndrome: increased postoperative survival risk in gastric cancer

Overweight/obesity and metabolic syndrome (MetS) are recognized as potential risk factors for gastric cancer, but their impacts on postoperative morbidity and overall survival (OS) following radical gastrectomy remain controversial. We hypothesized that overweight/obesity and MetS represent successive stages of a progressive metabolic disorder, and aimed to investigate the effects of preoperative overweight/obesity and MetS on postoperative complications and OS, as well as the additional survival risk associated with MetS on the basis of overweight/obesity. Five-hundred-fifty-seven patients with primary stage I–III GC who underwent radical gastrectomy at the First Hospital of Lanzhou University between January 2017 and December 2021 were enrolled. Subjects were classified into three groups: Group A (normal weight without MetS), Group B (overweight/obesity without MetS), and Group C (overweight/obesity with MetS). After propensity-score-based baseline matching, OS was compared among the three groups. Univariate and multivariate Cox regression analyses were performed to identify independent predictors of OS. Restricted cubic spline (RCS) models were used to characterize the dose–response relationship between BMI and post-operative complications; threshold analysis of BMI as a continuous variable was employed to determine the optimal cut-off for risk stratification. Compared with Group A, Group B showed no significant difference in OS ( P = 0.278), while Group C had a worse OS ( P = 0.033). Although OS in Group C was lower than in Group B, the difference was not statistically significant ( P = 0.163). BMI displayed a U-shaped, non-linear association with post-operative complication rates ( P = 0.007); Threshold analysis revealed that both low and high BMI increased the risk of complications and identified the optimal cut-off value of BMI as 22.82 kg/m². Among patients with BMI ≥ 22.82 kg/m², complication rates rose progressively with the cumulative number of MetS components; subjects with ≥ 2 metabolic abnormalities had a higher complication risk than those with 0–1 abnormality ( P = 0.033). The combination of MetS on the basis of overweight/obesity is associated with an increased risk of postoperative mortality in gastric cancer. Preoperative assessment combining BMI and metabolic components may help identify high‑risk individuals and guide targeted interventions.