A new study shows marked variations in the Chinese obesity epidemic for different geographical regions, urban/rural areas, gender and educational level.
Obesity is rapidly becoming a major health burden for China, where average body mass index (BMI)* and obesity rates in adults have increased steadily from the 1980s onwards. Since 2010, this has prompted government-led obesity prevention programmes, such as promoting better diets and lifestyles and providing incentives to increase the production of healthier foods.
A new study, led by NDPH researchers and colleagues at the Chinese Center for Disease Control and Prevention, has assessed whether these have been effective in slowing the increase in average BMI and obesity prevalence in Chinese adults. The results, published today in The Lancet, provide robust new evidence about the evolving obesity epidemic in China, not only overall but across different regions and urban/rural settings.
For this analysis, the researchers used data from six nationwide surveys conducted between 2004 and 2018. In total, this included 645,223 participants aged 18-69 years old. The mean BMI and the prevalence of obesity was calculated for the different time points used in the surveys, with comparisons made for gender, education, urban/rural location and geographical region.
Key results:
- Between 2004 and 2018, the total number of adults who were obese in China more than tripled, reaching an estimated 85 million adults (48 million men and 37 million women). During this period, average BMI rose from 22.7 kg/m² to 24.4 kg/m², and obesity prevalence from 3.1% to 8.1%.
- These trends in BMI and obesity prevalence were beginning to slow in urban populations, but less so for rural regions. In particular, BMI and obesity prevalence continued to rise steadily for rural women, overtaking that of urban women by 2018.
- There were also persistent north–south gradients in average BMI and obesity prevalence. People living in northern China had a mean BMI more than 2 kg/m² higher than their counterparts in southern China.
- For both urban and rural women, education may have a protective effect. Compared with women with the lowest level of education, the mean BMI for women with the highest level of education was between 1.6 and 1.8 kg/m² lower, and the prevalence of obesity between 20 and 30% lower.
- For men, however, the association with education was reversed. Men with the highest level of education had an average BMI around 1.1 kg/m² higher and an obesity prevalence more than 100% higher than those with the lowest level of education.
According to the researchers, the drivers underlying these regional and gender-specific variations likely reflect many factors, including differences in economic development; changing patterns of physical activity; and consumption of high-calorie and animal-based foods. For instance, the proportion of people working in agricultural and manual occupations decreased significantly during the study period, from 60% in 2004 to 38% in 2018.
In addition, over recent years rural residents may have spent disproportionately more of their increased income on high-calorie foods than urban residents, having initially had lower incomes. In urban areas, however, higher educational levels may lead to people making healthier dietary choices.
Lead author Professor Zhengming Chen said: ‘As China continues to modernise and become more urbanised, obesity and the associated health burdens (including hypertension and diabetes) are likely to become more and more of an issue, particularly in rural areas. Our study findings highlight the need to continue monitoring longer-term trends and regional differences, to develop more targeted and effective prevention strategies in both urban and rural Chinese populations.’
*Body mass index (BMI) is a measure of weight relative to a person’s height. It is calculated by dividing a person’s weight (in kilograms) by the square of their height (in metres). A BMI between 18.5 and 24.9 kg/m² is considered a healthy weight; a BMI between 25 and 29.9 kg/m² is classed as overweight; and a BMI greater than 30 kg/m² is classed as obese.