Objective:To investigate the association between quantified CT (QCT)-measured body composition and metabolic syndrome (MS) components in obese populations before bariatric surgery.Methods:A cross-sectional study. A retrospective analysis was conducted on a cohort of 97 obese patients scheduled for weight-loss surgery at the First Affiliated Hospital of Wannan Medical College from January 2021 to March 2023. The patients′ body mass index (BMI), biochemical parameters and body composition measurements obtained by QCT were recorded. The patients were stratified into groups based on gender, obesity severity and the number of MS components. Differences in body composition among the groups were compared. Additionally, the correlations between each body composition parameter and metabolic indicators were analyzed. The diagnostic efficacy of each body composition parameter for identifying obese individuals with different MS components was assessed using receiver operating characteristic (ROC) curve analysis.Results:There were 75 females (77.3%). Male obese patients had higher total abdominal fat area [(693.23±148.90) vs (574.99±114.89) cm 2, t=-3.958, P<0.001], visceral fat area [(289.65±57.67) vs (195.60±57.37) cm 2, t=-6.753, P<0.001], fat content of pancreatic head [27.45%(21.65%, 45.48%) vs 21.60%(17.6%, 26.9%), Z=-2.675, P=0.007], and skeletal muscle index [73.36(68.74, 81.26) vs 61.52(55.74, 66.41) cm 2/m 2, Z=-5.246, P<0.001]. With the increase of obesity, abdominal fat mainly increases in subcutaneous fat. With the increase of MS components (MS2 group, MS3 group, MS4 group, MS5 group), the abdominal fat area, abdominal fat/subcutaneous fat, liver fat content, pancreatic head fat content, and skeletal muscle index of patients all increased accordingly. In diagnosing the presence of two components of MS, area under the curve of visceral fat area was the largest (AUC=0.706, 95% CI=0.577-0.834). For diagnosing the presence of three, four and five components of MS, area under curve of liver fat content were all the largest (MS3=0.712, 95% CI=0.605-0.818; MS4=0.652, 95% CI=0.537-0.766; MS5=0.706, 95% CI=0.576-0.836). Conclusion:There are differences in QCT body composition among obese patients with different MS components, and there is a correlation between each body composition and MS component. Among them, intra-abdominal fat area and liver fat content are of great value in evaluating obese patients with different MS components.