Heterogeneous effects of working time reduction on overweight: Evidence from France.

We examine the impact of a statutory reduction in working time (WTR) on overweight and obesity among white- and blue-collar workers in a large French firm. The firm implemented a 35-hour workweek one year prior to the national reform in all regions except Alsace-Moselle, where statutory WTR was smaller due to differences in the calculation of public holidays and working-time norms. We find that the WTR had heterogeneous effects across workers. Among blue-collar employees, the reform increased the likelihood of being overweight by 6.7 percentage points (pp) and reduced obesity by 2.6 pp. In contrast, no average effects are found among white collar workers. The heterogeneity analysis by baseline Body Mass Index (BMI) reveals contrasting patterns across occupations: among blue-collar workers, the increase in overweight is driven by individuals who were initially of normal weight, whereas among white-collar workers, overweight declines significantly only among those who were overweight or obese at baseline. Overall, the results suggest that the effects of WTR vary systematically with the baseline level of occupational sedentariness.