Introduction Poor psychosocial working conditions and unhealthy behaviors are known determinants of poor health. The objective of this study is to examine the mediating role of unhealthy behaviors and body mass index (BMI) in the relationship between high job strain and self-rated poor health in workers with a low educational level.

Methods A total of 8,369 low educated workers, who participated in the Lifelines cohort study during the period 2012–2017, were included. Self-reported job strain, health behaviors (smoking, physical activity, fruit and vegetable consumption) and BMI were assessed at baseline, and self-rated health after 2 years. To assess mediation by the health behaviors and BMI, structural equation modeling with logistic and multinomial regression analyses were performed.

Results Workers with high job strain had a higher odds of poor health (OR 1.34; 95%CI 1.13–1.60) compared to those with low job strain. Workers with high job strain were more likely to have a lack of physical activity (OR 1.14; 95%CI 1.01–1.28), but were not more likely to smoke, to be overweight or obese, or to have a low fruit or vegetable consumption. Workers who smoked (OR 1.37; 95%CI 1.16–1.60), had a lack of physical activity (OR 1.25; 95%CI 1.08–1.43) or were overweight (OR 1.37; 95%CI 1.16–1.61) or obese (OR 2.25; 95%CI 1.86–2.72) were more likely to report poor health. Indirect (mediating) effects of unhealthy behaviors and BMI in the relationship between high job strain and poor health were small and not statistically significant.

Conclusion No mediating effects of unhealthy behaviors or BMI were found in the relationship between high job strain and self-rated poor health among workers with a low educational level.