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

Key words: 
• BMI /
• BF％ /
• Obesity

Abstract: 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 BMI and WHO BF% definitions for obesity was poor for both men (kappa: 0.210, 95% CI: 0.179-0.241) and women (kappa: 0.327, 95% CI: 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% CI: 1.43-5.81), or in subjects with high BMI (BMI≥28 kg/m2) (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/m2) respectively. No difference in risk could be found in those with intermediate BMI (BMI: 24-27.9 kg/m2) (RR: 1.44, 95% CI: 0.86-2.40), as compared to those with low BMI (BMI<24 kg/m2), 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/m2.