Does Working Long Hours Cause Obesity? The Case of the Reduction in South Korea’s Standard Workweek

Abstract

Background: Despite its significant policy implications, not much is known about the causal impact of working long hours on obesity. The available evidence is mixed due to biases associated with omitted variables, reverse causality, and sample selection. Owing in part to this lack of conclusive evidence, the standard workweek—which sets the maximum weekly work hours for full-time salaried workers and, therefore, tends to limit their overtime work—has received little attention as a policy tool for tackling obesity. Between 2004 and 2011, the Korean government reduced the standard workweek from 44 to 40 hours for larger establishments, followed by smaller ones. We examine how this four-hour reduction affected body mass index (BMI) and obesity among male workers. Methods: The longitudinal data for workers come from the 2005, 2007, and 2008 waves of the Korea Labor and Income Panel Study (N = 1,383 persons or 3,977 person-years). Taking advantage of the gradual expansion of the 40-hour standard, we estimate its causal impact: Our key independent variable is a binary indicator of whether the standard workweek for a worker was reduced to 40 hours in each year given the timeline of the policy intervention, depending on establishment size. We estimate the impact on BMI with linear regressions and on obesity with logistic regressions. Results: The reduction to the 40-hour standard lowered both BMI (β = -0.220; 95% confidence interval [CI] -0.449 – 0.010; P-value = 0.061) and obesity (odds ratios [OR] = 0.785; 95% CI 0.627 – 0.985; P-value = 0.036). As a plausible pathway underlying the effects, we also found that the policy change reduced workers’ actual workweeks by 2.5 hours (β = -2.526; 95% CI - 3.542 – -1.509; P-value < 0.001). Conclusions: Working longer hours is speculated to increase obesity due to less exercise, unhealthy eating habits, sleep deprivation, and increased sedentariness. By demonstrating the decline in BMI and obesity as a result of the reduced standard workweek in Korea, we suggest that government regulation of the maximum work hours and the enforcement of corporate compliance with the regulations would be effective occupational interventions for overcoming obesity