Systemic Inflammatory Response Index Is Associated With Insufficient Weight Loss After Bariatric Surgery

Obesity is a chronic disease characterized by a persistent low-grade inflammatory state. The systemic inflammatory response index (SIRI) is a novel biomarker of systemic inflammation. This study aimed to evaluate SIRI evolution before and 1 year after bariatric surgery and to assess its association with insufficient weight loss (IWL).

An observational study was conducted including all patients who underwent bariatric surgery at a university hospital between 2013 and 2023. Preoperative and 1-year postoperative data were collected, including demographics, comorbidities, anthropometric parameters, surgical technique, complications, and SIRI values. Changes in these variables and their association with IWL were analyzed.

A total of 348 patients were included, 116 men (33.3%) and 232 women (66.7%), with a median age of 46 years (IQR 39-46). Sleeve gastrectomy was performed in 196 patients (56.3%) and Roux-en-Y gastric bypass in 152 (43.7%). Baseline weight (p < 0.001) and BMI (p = 0.005) were significantly associated with preoperative SIRI. Postoperative SIRI correlated with weight, BMI, and %EWL at 1 year (all p < 0.001). Higher postoperative SIRI values were significantly associated with IWL, both by %EWL < 50% (p = 0.008) and Reinhold's classification (p = 0.017). In multivariate analysis, higher SIRI at 1 year (p = 0.006; OR 0.27 and 95% CI 0.10-0.69), older age (p = 0.004; OR 0.96 and 95% CI 0.93-0.99), and female sex (p = 0.019; OR 0.52 and 95% CI 0.30-0.90) were independently associated with IWL.

SIRI is closely associated with weight and BMI in patients with obesity and decreases after bariatric surgery, reflecting improved inflammatory status. Higher postoperative SIRI is independently associated with IWL, suggesting that persistent inflammation may contribute to poor surgical outcomes.