OBESITY

Obesity is a major risk factor for cardiovascular disease, diabetes, hypertension and premature death. The body mass index (BMI) is a widely accepted measure of weight-for-height. Generalised obesity is defined as BMI greater than 30 kg/m2. However BMI does not take account of the distribution of fat around the abdomen, which has been recognised as a risk factor in relation to chronic diseases. For this, the waist-hip ratio (WHR) is used, a measure of central obesity. Central obesity is defined as a WHR of 0.95 or greater in men, and of 0.85 or greater in women.

The observed prevalence of generalised obesity in men was lowest for the Bangladeshi and Chinese groups (5.4% and 6.2%). Rates of obesity in Indian (11.9%) and Pakistani (12.6%) men were about twice those of the Bangladeshi group, but still lower than the general population. Around a fifth of men in the Irish (20.4%) and Black Caribbean (18.3%) groups were obese, a similar proportion as for the general population (18.9%).
The chart shows age-standardised risk ratios for obesity, and confirms these findings. The risk of obesity in the South Asian and Chinese groups ranged from 0.32 for Bangladeshi men to 0.74 for Pakistani men, all significantly lower than the general population.

Among women, the proportion classified as obese was again very low in the Chinese (4.5%) and Bangladeshi (9.5%) groups. Around a fifth of women in the general population (20.9%) and in the Indian (19.6%) and Irish (21.2%) groups were obese. Levels of generalised obesity significantly higher than in the general population were found in the Pakistani (25.6%) and Black Caribbean (31.9%) groups. The age-standardised risk ratios confirm these findings. Black Caribbean and Pakistani women were around 60% more likely to be classified as obese than women in the general population (risk ratios 1.60 and 1.61), while Bangladeshi women were 40% (risk ratio 0.63) and Chinese women 80% (risk ratio 0.20) less likely to be obese.

Looking at the prevalence of central obesity (raised WHR), among men it ranged from 17.9% in Chinese men to 36.1% in Indian men, compared with the general population level of 27.5%. South Asian men, although their prevalence of generalised obesity was lower, had higher levels of central obesity than men in the general population (risk ratios for raised WHR ranging from 1.33 for Bangladeshi men to 1.54 for Pakistani men). Chinese (risk ratio 0.76) and Black Caribbean (0.62) men had significantly lower rates of central obesity than the general population.

Among women, all the minority ethnic groups had levels of central obesity significantly higher than in the general population (19.9%), ranging from 24.9% among Irish women to 42.8% among Bangladeshi women. Age standardisation confirmed these findings, and showed that Black Caribbean (risk ratio 2.09), Pakistani (2.79) and Bangladeshi (3.63) women were at least twice as likely as women in the general population to be centrally obese, while Chinese (1.79) and Indian (1.73) women were three-quarters more likely.

Source: The Health Survey of England 1999