The study classified 83 obese adults by constitution and had them follow a strict diet according to their constitution in order to see if the Yin-Yang method would be effective on the metabolic syndrome, which is one of the main causes of death in Korea. Overall, the application of both Yin and Yang methods improved the following factors: weight, body fat percentage, systolic blood pressure, diastolic pressure, neutral fats and total cholesterol. In particular, the Yin constitution group of men showed more improvements than the Yang constitution group. Furthermore, waist circumference and the prevalence rate of systolic blood pressure, diastolic pressure, total cholesterol and metabolic syndrome were decreased noticeably. Total energy intake was increased in both men and women after the constitutional diet, along with the increase of nutrient intake, such as dietary fiber, vitamins and minerals, among others. Among various nutrients, vitamin A, vitamin C, thiamine, vitamin B6, folic acid, calcium, phosphorus, potassium, magnesium and iron intake were increased noticeably after the constitutional diet. In addition, subjects' intake of all nutrients, except for magnesium, satisfied the nutrition intake standards. Further, the nutrients adequacy ratio (NAR) and the mean adequacy ratio (MAR) improved for both men and women. The intake of potatoes, starch, greens and mushrooms increased noticeably, whereas the intake of meat, dairy, drinks and alcohol decreased after the constitutional diet. For the Yin constitution, the intake of Yin foods noticeably decreased, where as the intake of Yang foods decreased for the Yang constitution. In conclusion, the constitutional diet effectively improves the metabolic syndrome. Among many nutrients, the intake of dietary fiber, vitamins A, C and E, potassium and magnesium is positively associated with the improvement of metabolic syndrome biomarkers.