Ethnic differences in the relationships between obesity and glucose-metabolic abnormalities: a cross-sectional population-based study

OBJECTIVES: To evaluate whether body mass index (BMI) and other anthropometric indices of visceral obesity vary by ethnic group in their distribution and their relationship to metabolic abnormalities. DESIGN: Cross-sectional study. PARTICIPANTS: Canadian men and women, aged 35 - 75 years, of South Asian (n = 342), Chinese (n = 317), European (n = 326) and Aboriginal (n = 301) descent were recruited using stratified random sampling. PRIMARY MEASURES: Anthropometric indices (BMI, waist to hip ratio (WHR) and waist circumference (WC)), metabolic markers ( fasting glucose, HbA1c, the ratio of total cholesterol/HDL) and clinical markers (systolic blood pressure) were assessed. RESULTS: In subjects with BMI < 30 kg/m2, the mean marker levels in people with elevated WC (> 88cm in women, > 102 cm in men) vs people with normal WC were 6.16 vs 5.34 mmol/l for fasting glucose, 6.05 vs 5.66% for HbA1c and 5.46 vs 4.68 for the ratio of total cholesterol to HDL (P < 0.001 in each case). At nearly every given level of BMI, non-European ethnic groups displayed significantly higher marker levels than Europeans. For example, for a given BMI, age and sex, the difference between European and non-European groups in HbA1c levels was 0.53% (95% confidence interval (Cl): 0.37 - 0.69) for South Asians, 0.37% (95% Cl: 0.2 - 0.54) for Chinese and 0.95% ( 95% Cl: 0.78 - 1.12) for Aboriginal People. CONCLUSIONS: Uniform cut-points for the classification of obesity using BMI, WHR or WC result in marked variation in the levels of glucose-metabolic abnormalities between ethnic groups. Existing action thresholds for these anthropometric indices do not apply to non-European ethnic groups and warrant revision. International Journal of Obesity (2005).