Impact of Preoperative Muscle and Fat Indices on Post-Sleeve Gastrectomy Weight Loss

Obesity, a chronic disease characterized by pathological fat accumulation, requires effective therapeutic strategies. While sleeve gastrectomy (SG) demonstrates superior efficacy for sustained weight loss, clinical guidelines lack integration of objective body composition metrics used in chronic disease management. This study aims to investigate the relationship between preoperative body composition and postoperative weight loss outcomes in patients undergoing SG.

Patients with obesity who underwent SG at our center between October 2019 and May 2024 were enrolled. Preoperative body composition was assessed using abdominal computed tomography (CT) and bioelectrical impedance analysis (BIA). Weight loss outcomes were evaluated using body mass index (BMI), percentage of excess weight loss (%EWL), and percentage of total weight loss (%TWL). Regression and receiver operating characteristic (ROC) analyses were performed to identify predictors of surgical success.

In a study of 315 individuals (63.5% female). CT analysis showed that males had significantly higher core muscle mass, including psoas major index (10.71 ± 2.35 vs. 7.12 ± 1.54 cm²/m², p < 0.001) and abdominal wall muscle index (58.19 ± 7.51 vs. 46.69 ± 5.83 cm²/m², p = 0.01), with no significant sex differences in fat distribution. Female patients achieved higher 1-year %EWL than males (1.162 ± 0.491 vs. 1.021 ± 0.513, p < 0.001). Multivariate regression identified age (OR = 0.925, 95% CI 0.861-0.993; p = 0.032), wall muscle area (OR = 0.557, 0.349-0.888; p = 0.014) and wall muscle index (OR = 4.214, 1.226-14.489; p = 0.02) as independent predictors of weight loss. The combined model had better predictive accuracy for percent weight loss than body mass index alone (AUC = 0.840 vs ≤ 0.682; p < 0.001).

Preoperative body composition, particularly core muscle mass and subcutaneous fat distribution, is strongly associated with postoperative weight loss outcomes after SG. CT-based assessments may offer valuable prognostic insight predict surgical outcomes and adjust interventions accordingly.