Wu Fei pointed out in the second issue of society in 2021 that many studies have revealed gender differences in the relationship between socioeconomic status and obesity: for women, the higher the socioeconomic status, the lower the probability of obesity; For men, the higher the socioeconomic status, the more likely they are to be obese. There may be two sources for this correlation: the social determinant hypothesis holds that socioeconomic status is the fundamental cause of obesity, and the direction of causality is from socioeconomic status to obesity; On the contrary, the "healthy choice hypothesis" holds that the labor market will be screened according to people's body shape, and the causal direction is from obesity to socio-economic status. This paper points out that there are obvious gender differences in the causal relationship between socioeconomic status and obesity: for men, the positive correlation found in previous studies comes from the process of "social decision" and "body screening"; For women, the negative correlation in the existing studies mainly comes from the "body screening" process.