Subjective Workload and the Metabolic Syndrome: An Exploration of the Mediating Role of Burnout and the Moderating Effect of Physical Activity

In this study, building on Hobfoll's (1989) conservation of resources theory, we aimed to reveal the effect of subjective workload at baseline on the likelihood of developing new-onset of metabolic syndrome (MetS), a cluster of cardiovascular risk factors during follow-up. We also aimed to find out whether an increase in job burnout mediates this association, and whether the extent of engagement in leisure-time physical activity (PA) attenuates the effect of workload on MetS. Using a three-wave longitudinal study design, we followed a sample of 1,966 Israeli employees free of MetS at baseline for 3.5 years on average. We controlled for multiple confounders, including objective workload (i.e., work hours). Subjective workload at baseline was associated with the risk of new-onset of MetS, yet this association was moderated by PA. Specifically, among participants with low PA (37 weekly minutes), a one-point increase in our five-point measure of subjective workload was associated with a 41% increase in risk of new-onset MetS, whereas among those with high PA (258 weekly minutes) it was associated with a 38% reduction in risk. Among participants who engaged in 148 weekly minutes of PA (as recommended by the U.S. Department of Health and Human Services), an increase in workload did not result in an increased risk of developing MetS. We did not find, however, any indication for a mediating effect of job burnout. Our findings suggest that engaging in PA while being overloaded not only protects employees from adverse outcomes but actually reverses the cardiovascular risk.