Obesity and insulin resistance are associated with the risk of colon cancer. Adenomatous colonic polyps are precancerous lesions of colon cancer. We investigated whether BMI and the metabolic syndrome are associated with the presence of adenomatous colonic polyps in Korean men. Anthropometric measurements, metabolic risk factors, and colonoscopic pathologic findings were assessed in 1,898 men who underwent routine colonoscopy at the Health Promotion Center of Asan Medical Center in 2005. The modified National Cholesterol Education Program Adult Treatment Panel III (NCEP-ATP III) and International Diabetes Federation (IDF) criteria were used for the definition of the metabolic syndrome. Multiple logistic regression analysis was used to evaluate the association between BMI and the metabolic syndrome and adenomatous polyps. Compared with men in the 1st quintile of the BMI, the adjusted odds ratio (OR) and 95% confidence interval (CI) for adenomatous polyps in men in the 2nd, 3rd, 4th, and 5th quintiles of the BMI were 1.55 (1.10-2.19), 1.57 (1.10-2.24), 1.94 (1.34-2.81), and 1.99 (1.31-3.01), respectively (P for trend <0.0001). Men with triglycerides (TGs) > or = 150 mg/dl were significantly more likely to have adenomatous polyps than were men with TG <150 mg/dl (OR 1.29; 95% CI 1.03-1.62). As a function of the number of metabolic risk factors, the ORs for adenomatous polyps were 1.41 (1.03-1.93), 1.52 (1.08-2.12), 1.46 (1.01-2.12), and 1.77 (1.08-2.90) for 1, 2, 3, and > or = 4 risk factors, respectively (P for trend <0.05). Adenomatous colonic polyps were significantly associated with increased BMI levels. Subjects with even one component of the metabolic syndrome had a significantly higher risk for developing adenomatous polyps compared to those subjects without any component in Korean men.