The connection between working hours and body mass index in the US: a time use analysis

Over recent decades, Americans have transitioned from working in active jobs to working in sedentary jobs, and there have been dramatic increases in hours worked for certain demographic groups. While a body of research documents that time spent working is associated with increased body mass index (BMI), this paper explores possible mechanisms for that relationship using time use data. This paper finds that, for workers in non-strenuous jobs, 10 additional hours spent working are associated with an increase in BMI of 0.424 for women and 0.197 for men, representing an increase of 2.5 and 1.4 pounds, respectively. The paper does not find a relationship between working time and BMI for workers in strenuous jobs. For workers in non-strenuous jobs, the effect of time spent working on BMI becomes smaller after accounting for time spent sleeping for both men and women and time spent in exercise and food preparation for women only; the effect becomes larger after accounting for screen time for both men and women and time spent in secondary eating and commuting for women only. Screen time is the single time use channel associated with the largest differences in the estimated effect of time spent working on BMI for both women and men employed in non-strenuous jobs. After controlling for all time use channels, the effect of hours worked on BMI decreases for women, but increases for men. These findings suggest plausible mechanisms for the association between time spent working and obesity.