Manifestation of cardiovascular risk factors at low levels of body mass index and waist-to-hip ratio in Singaporean Chinese.

The global prevalence of obesity, characterised by a body mass index (BMI) >= 30 kg/m2, is high and is increasing. Obesity is associated with a higher risk of developing non-communicable diseases such as cardiovascular disease (CVD) and cancer. In Singapore the prevalence of obesity differs among the three main ethnic groups (Chinese, Malays and Indians) but is relatively low compared to Western societies. Despite the low prevalence of obesity (BMI >=30 kg/m2), the morbidity and mortality for CVD are high in Singapore. In this paper, the odds ratio for presence of risk factors for CVD was studied in relation to BMI quintiles and in relation to body fat distribution as measured by waist-to-hip ratio (WHR) quintiles in a representative sample of adult Singaporean Chinese. The lowest quintile was used as the reference category. The boundaries for the BMI quintiles were 18.9, 20.7, 22.6 and 25.0 kg/m2 for females and 20.0, 21.7, 23.5 and 25.6 kg/m2 for males. The boundaries for WHR quintiles were 0.68, 0.71, 0.74 and 0.79 for females and 0.77, 0.82, 0.85 and 0.89 for males. As observed in other studies, the odds ratios for high serum total cholesterol, low HDL cholesterol, high total cholesterol/HDL cholesterol ratio, high serum triglyceride level, high blood pressure and high fasting blood glucose were higher in upper BMI and WHR quintiles. The effects were more pronounced in males compared with females. The odds ratios for having at least one of the mentioned risk factors in the different BMI quintiles for females were 1.3 (not significant (ns)), 1.6, 2.1 and 2.7, while in males they were 2.7, 4.1, 6.2 and 7.3. For the WHR quintiles the odds ratios were 0.9 (ns), 1.3 (ns), 1.9 and 2.1 for females, while for males they were 2.1, 4.7, 6.7 and 12.6. As the elevated risks are already apparent at low levels of BMI and low levels of WHR, it can be queried whether the cut-off points for obesity based on BMI and for abdominal fat distribution based on WHR as suggested by the WHO are applicable to the Singaporean Chinese population. There are indications in the literature that Asian populations have higher body fat percentages at lower BMI. This may explain the high odds ratios for CVD risk factors at low BMI and WHR and the high morbidity and mortality from CVD in Singapore, despite relatively low population mean BMI and obesity rates.