Comparison of Body Mass Index with Body Fat Percentage in the Evaluation of Obesity in Chinese

Objective To evaluate the present Chinese body mass index (BMI) criteria with body fat percentage (BF%) in determining obesity in Chinese population. Methods A total of 4 907 subjects (age: 20-90 yrs) were enrolled in the baseline survey of a longitudinal epidemiological study, and 2 638 of them were reevaluated in 5.5 years later. The Chinese BMI and WHO BF% were used to define obesity, respectively. Results The diagnostic agreement between the Chinese BM I and WHO BF% definitions for obesity was poor for both men (kappa: 0.210, 95% Cl: 0.179-0.241) and women (kappa: 0.327, 95% Cl: 0.296-0.358). However, BMI had a good correlation with BF% both in men (r: 0.785, P<0.01) and women (r: 0.864, P<0.01). The age and sex-adjusted relative risks (RR) for incidence of type 2 diabetes (T2DM) were significantly higher in subjects with intermediate BF% (BF%:20.1%-25% for men, 30.1%-35% for women) (RR: 2.35, 95% CI: 1.23-4.48) and high BF%(BF%>25% for men and >35% for women)(RR: 2.89, 95% Cl: 1.43-5.81), or in subjects with high BMI (BMI >= 28 kg/m(2)) (RR: 2.46, 95% CI: 1.31-4.63) when compared to those with low BF% (BF%<= 20% for men and <= 30% for women) or low BMI (BMI <24 kg/m(2)) respectively. No difference in risk could be found in those with intermediate BMI (BMI: 24-27.9 kg/m(2)) (RR: 1.44, 95% CI: 0.86-2.40), as compared to those with low BMI (BMI<24 kg/m(2)), whose BF% ranged widely from 7.8 to 50.3%. Conclusion BMI was correlated with BF%. Both BMI and BF% were associated with high risk for T2DM. However, BMI had its limitations in the interpretation of subjects with BMI between 24 and 27.9 kg/m(2).