박용우,김철환, 신호철

성균관대학교 의과대학 가정의학교실

Background : Body mass index (BMI) is commonly used to identify obesity. A BMI of 25kg/m2 is considered the cut-off value of obesity in Asia, which is controversial. The aim of this study is to evaluate the appropriateness of BMI as a diagnostic tool of obesity and to assess the optimal BMI predicting abnormal % body fat. Methods : Percent body fat was measured by multi-frequency bioelectric impedance analysis in 901 adults (men, 377; women, 524), aged 18 yr and above, who visited obesity clinic from March 1998 till August 2000. Results : Obesity defined by BMI of 25 kg/m2 was 72.9% among men, 70.6% among women. However, 45.2% of men and 27.5% of women with a BMI 25~27kg/m2 were non-obese as defined by % body fat. Age-adjusted partial correlations between BMI and % body fat were significantly lower in subjects below 30 of BMI (r=0.18~0.4), compared to subjects above 30 of BMI (r=0.73~0.78). Using ROC analysis, the BMIs corresponding to the cut-off values of % body fat (25% for men, 33% for women) were 26.7, 27.1, respectively. Conclusion : BMI cut-off value to define obesity in Korea should be 27 instead of 25. To identify obesity among at-risk populaton (BMI between 23~27), another screening tools such as waist circumference should be included, or body fat measurement should be considered. Key words: body mass index, percent body fat, bioelectric impedance analysis