This study was designed to investigate the anti-obesity and anti-atherosclerotic effects of supplementation with Chungkookjang (CKJ), a traditional fermented soybean food, in overweight/obese subjects. The study was a 12-week, randomized, double-blind, placebo-controlled clinical trial followed by a 3-week screening period. Overweight/obese subjects (both groups having a body mass index ≥23 kg/m(2) and waist hip ratio of ≥0.90 for men and ≥0.85 for women) who were not diagnosed with any disease were included in this study. Sixty subjects were randomly divided into a CKJ (n=30, 26 g/day) or placebo (n=30) group. During the 12-week intervention period, subjects were asked to maintain their usual diet and activity and not to take any functional foods or dietary supplements. Anthropometric parameters, abdominal fat distribution by computerized tomography, and blood parameters (lipid profile, atherosclerotic indices) before and after the 12-week intervention period were measured. Fifty-five subjects (29 CKJ group, 26 placebo group) finished the study. After the 12 weeks of supplementation, subjects in the CKJ group showed a significant improvement in apolipoprotein B (P<.05) compared with the placebo group. Visceral fat areas by computerized tomography scans and apolipoprotein B/apolipoprotein A1 showed a tendency to decrease in the CKJ group, but there were no significant differences between the CKJ and placebo groups. These results suggested that CKJ supplementation has potential anti-atherosclerotic effects that might be more pronounced when combined with lifestyle modification.