Effect of kochujang (Korean red pepper soybean paste) on the reduction of body weight and lipid levels of adipose tissues and serum were investigated in the rats fed a high-fat diet. Male Sprague-Dawley rats were fed for four weeks with diets containing either a normal diet (ND, based on the AIN-76TM diet), high fat diet (HFD, supplemented with 20% corn oil in ND), CK diet (10% commercial kochujang in HFD), TK I diet (10% 0 day (non-) fermented traditional kochujang in HFD), TKII diet (10% 6-month fermented traditional kochujang in HFD), or RPP diet (3% red pepper powder in HFD). CK, TK I and TKII in the diet significantly reduced the body weight gain compared to the control (HFD), whereas red pepper powder had no such effect. TKII supplementation in the high-fat diet reduced epididymal and perirenal fat pad weight significantly (p<0.05). Liver total lipid was lower in TKII diet group than other kochujang and RPP diet groups. TKII and CK decreased the content of triglyceride in epididymal and perirenal fat pad that increased by high-fat diet. The cholesterol content of the perirenal fat pad was the lowest in the TKII diet group. TKII was also effective in lowering serum cholesterol level. These results indicated that properly ripened (fermented for 6-month) traditional kochujang exhibited more suppressive effects on body fat gain and lipid levels of adipose tissue and serum than RPP, commercial kochujang and the kochujang without fermentation.