British Journal of Nutrition

Research Article

Lower BMI cut-off value to define obesity in Hong Kong Chinese: an analysis based on body fat assessment by bioelectrical impedance

Gary T.C. Koa1 c1, Joyce Tanga2, Juliana C.N. Chana3, Rita Sunga4, Morris M. F. Wua5, Hendena P.S. Waia5 and Raymond Chena1

a1 Department of Medicine, Alice Ho Miu Ling Nethersole Hospital, 11, Chuen On Road, Tai Po, Hong Kong

a2 United Christian Nethersole Community Health Service, Hong Kong

a3 Department of Medicine and Therapeutics, Prince of Wales Hospital, Chinese University of Hong Kong, Hong Kong

a4 Department of Paediatrics, Prince of Wales Hospital, Chinese University of Hong Kong, Hong Kong

a5 Pamela Youde Nethersole Eastern Hospital, Hong Kong


There is increasing evidence suggesting that the cut-off values for defining obesity used in the Western countries cannot be readily applied to Asians, who often have smaller body frames than Caucasians. We examined the BMI and body fat (BF) as measured by bioelectrical impedance in 5153 Hong Kong Chinese subjects. We aimed to assess the optimal BMI reflecting obesity as defined by abnormal BF in Hong Kong Chinese. Receiver operating characteristic curve (ROC) analysis was used to assess the optimal BMI predicting BF at different levels. The mean age and SD OF THE 5153 SUBJECTS (3734 WOMEN AND 1419 MEN) WAS 51.5 (sd 16.3) years (range: 18.0–89.5 years, median: 50.7 years). Age-adjusted partial correlation (r) between BMI and BF in women and men were 0.899 (P<0.001) and 0.818 (P<0.001) respectively. Using ROC analysis, the BMI corresponding to the conventional upper limit of normal BF was 22.5–23.1 kg/m2, and the BMI corresponding to the 90 percentiles of BF was 25.4–26.1 kg/m2. Despite similar body fat contents, the BMI cut-off value used to define obesity in Hong Kong Chinese should be lower as compared to Caucasians. We suggest a BMI of 23 kg/m2 and 26 kg/m2 as the cut-off values to define overweight and obesity respectively in Hong Kong Chinese.

(Received May 26 2000)

(Revised September 15 2000)

(Accepted October 06 2000)


c1 * Corresponding author: Gary T. C. Ko, fax (852) 2689-2785, email: