Does income have a non-linear impact on residents’ BMI? Re-examining the obesity Kuznets curve

The results suggest that the impact of income on resident obesity may be related to dietary behaviour and health investment. Although income increases the likelihood of health expenditure and exercise, it has an inverted U-shaped effect on whether residents consume fish, meat, fried or pickled foods, and dine out. That is, in the low-income stage, income mainly increases consumption of unhealthy foods such as fish, meat, and fried and pickled foods, leading to a significant increase in BMI. In the high-income stage, residents reduce consumption of large amounts of fish and meat, pay more attention to healthy diet and healthcare, and increase exercise, which leads to a decline in BMI and an overall inverted U-shaped impact of income on obesity. Further heterogeneous analysis showed that income has a greater impact on obesity among rural residents, those aged 50 years and older, and those with low education levels. Finally, this study provides relevant suggestions for the prevention and control (P&C) of obesity among urban and rural residents.