Cross-national comparison of childhood obesity: The epidemic and the relationship between obesity and socioeconomic status

Background. Obesity has become a worldwide epidemic. Recently WHO acknowledged an urgent need to examine child obesity across countries using a standardized international standard. Studies in adults find obesity and socioeconomic factors (SES) factors are correlated, but results are inconsistent for children. Using an international standard, we examined the prevalence of obesity and compared the associations between SES factors and obesity across countries. Methods. Data for children aged 6-18 from nationwide surveys in the US (NHANES III, 1988-1994), China (1993), and Russia (1992) were used. We used the recently updated US NCHS body mass index (BMI = wt/ht²) reference to define obesity (BMI≥95th percentile) and overweight (85th≤BMI<95th percentile). The WHO recommends an early version of the NCHS reference for international use. We conducted logistic analyses to examine the relationship between SES and obesity. Results. The prevalence of obesity and overweight was 11.1% and 14.3%, respectively, in the US, 6.0% and 10.0% in Russia, and 3.6% and 3.4% in China. The relationship between obesity and SES varied across countries. Higher SES subjects were more likely to be obese in China and Russia, but in the US low-SES groups were at a higher risk. Obesity was more prevalent in urban areas in China but in rural areas in Russia. Conclusions. Child obesity is becoming a public health problem worldwide, but the prevalence of obesity varies remarkably across countries with different socioeconomic development levels. Different SES groups are at different risks, and the relationship between obesity and SES varies across countries.