Objective To examine the changing trends of body mass index (BMI) distribution in Chinese adults from 1989 to 2011. MethodsThe data from the China Health and Nutrition Survey (CHNS) collected in 1989, 1991, 1993, 1997, 2000, 2004, 2006, 2009 and 2011 were used. A total of 14831 participants aged 18-45 years with 39497 observations were included in the final analysis. Lambda-mu-sigma (LMS) method was applied to describe the changes of BMI distribution.ResultsFrom 1989 to 2011, the distribution curve of BMI showed shifts toward the right in both men and women. All percentile curves displayed an increasing trend and the change was much larger at higher percentile levels mainly among men. The median values of BMI and the prevalence of overweight and obesity exhibited increasing trends in both genders, especially in the period from 1997 to 2011. The quartile range of BMI increased from 3.4kg/m2 to 4.8kg/m2 for men and from 3.7kg/m2 to 4.4 kg/m2 for women. The prevalence of overweight and obesity appeared to be higher in three megacities than in nine provinces in both men and women. ConclusionAs indicated by the changes of the BMI distribution in Chinese adults, the prevalence of overweight and obesity increased greatly during the past 23 years, especially in men. It is urgent to take strategies for obesity prevention and control immediately in China.