Background: Body mass index (BMI) is internationally accepted as an index of degree of overweight and obesity. Because Asian have different body frame and lower average BMI than whites, the classification of overweight and obesity recommended by the World Health Organization cannot be directly applied to Korean. Therefore we estimated ideal BMI and determined the level of BMI for obesity management in Korean.
Methods: We investigated 9,990 men and women who visited a health promotion center, in the period May 1996 to May 1999. Thirteen medical problems served as indices of morbidity: hypertension, dyslipidemia, impaired fasting glucose, hyperuricemia, gallstone, liver disease, urinary tract infection, fatty liver, anemia, heart disease, gastrointestinal disease, lung disease, and renal disease. BMI (kg/m²) versus morbidity index was plotted and quadratic regression curve was drawn. Value of BMI at the lowest point of the curve was defined as ideal BMI. The prevalence odds ratio was estimated in each categories of BMI based on value of ideal BMI.
Results: Value of BMI at the lowest morbidity was 20.6 kg/m² in men and 19.5 kg/m² in women, and prevalence odds ratio of BMI showed significant increase in morbidity above 23∼24 kg/m² in men and 22∼23 kg/m² in women.
Conclusion: We propose that ideal BMI is 21 kg/m² in men and 20 kg/m² in women, and the level of BMI for obesity management is 23∼24 kg/m² in men and 22∼23 kg/m² in women.

Keywords: Body mass index, Morbidity, Obesity