Income-related inequities of adult obesity and central obesity in China: evidence from the China Health and Nutrition Survey 1997-2011

Objectives The aim of this study was to analyse the status regarding inequities in adult obesity and central obesity in China. Thus, income-related inequality for both diseases and the underlying factors were examined. Methods and design The China Health and Nutrition Survey (CHNS)-conducted from 1997 to 2011-included 128 307 participants; in this study, 79 566 individuals classified as obese and 65 250 regarded as suffering from central obesity according to the CHNS were analysed. A body mass index greater than 27 was considered indicative of obesity; men and women with a waist circumference of more than 102 cm and 80 cm, respectively, were considered as suffering from central obesity. The concentration index was employed to analyse inequality in adult obesity and central obesity. The decomposition of this index based on a probit model was used to calculate the horizontal inequality index. Results The prevalence of adult obesity increased from 8.34% in 1997 to 17.74% in 2011, and that of central obesity increased from 6.52% in 1997 to 16.79% in 2011. The horizontal inequality index for adult obesity decreased from 0.1377 in 1997 to 0.0164 in 2011; for central obesity, it decreased from 0.0806 in 1997 to -0.0193 in 2011. The main causes of inequality for both diseases are, among others, economic status, marital status and educational attainment. Conclusions From 1997 to 2011, the prevalence of adult obesity and central obesity increased annually. The pro-rich inequalities in both adult and central obesity decreased from 1997 to 2011. The inequality in central obesity was more prominent in the low-income group in 2011. Future policies may need to address obesity reduction among the poor.