Background: Recently, the International Diabetes Federation (IDF) consensus proposed a new definition for diagnosing metabolic syndrome. Ethnic-specific waist circumference (WC) cut-off points have been incorporated into the definition. Therefore, the study of the WC cut-off points for defining abdominal obesity in Koreans was performed by the Korean Society of the Study of Obesity.
Methods: The data used for analysis was from the Korean National Health and Nutritional Examination Survey (KNHANES) performed in 1998 (involved 6562 participants), which is representative of nutritional health research in Korea. The 2005 International Diabetes Federation definition of the metabolic syndrome was applied. The reasonable cut-off points of WC for abdominal obesity in Koreans were set based on Receiver Operating Characteristics (ROC) curve, odds ratio and prevalence of abdominal obesity in the study population.
Results: Using ROC analysis, the optimal WC to predict the risk factors of metabolic syndrome, such as high triglyceride levels, low levels of HDL-cholesterol, hypertension, and high glucose levels in Koreans, was 82~84 cm for men, and 79~82 cm for women. The odds ratio of having more than 2 metabolic abnormalities was about 5 in men with WC > 90 cm and in women with WC > 80 cm. WC in the 80th percentile in the Korean population is 90 cm and 86.5 cm for men and women, respectively.
Conclusions: The cut-off points of WC for abdominal obesity in Koreans are 90 cm for men and 85 cm for women, respectively. The cut-off points of waist circumference for defining abdominal obesity should be followed up by future additional studies and updated when new data becomes available.

Keywords: Metabolic syndrome, Obesity, Prevalence, Waist circumference