This study estimates the impacts of income on body mass indices (BMIs) of male and female adults from both urban and rural areas in China under the neoclassic theory of obesity, using China Health and Nutrition Survey data during 1991–2011.  Results of this study show that incomes has a significant inverted U-shaped impact on weight for both urban and rural males while having a negative effect on weight for urban females and positive effect on BMI for rural female, suggesting that further income growth is expected to lead to continuing growth of obesity for both urban and rural male adults as well as for rural female adults.  Moreover, the strenuousness of physical activity, which is represented by types of jobs, significantly reduced the BMI for all adults except for urban females, implying that a decrease in the strenuousness of physical activity stemming from economic development and technological changes is an important factor leading to the growth of obesity for all adults and rural female adults.