Association of Shift Work with Normal-Weight Obesity in Community-Dwelling Adults

Background: Shift work is associated with obesity and metabolic syndrome. However, this association in the normal-weight population remains unclear. This study aimed to investigate whether shift work is associated with normal-weight obesity (NWO).Methods: From the nationally representative Korea National Health and Nutrition Examination Survey (KNHANES) dataset (2008 to 2011), 3,800 full-time workers aged >= 19 years with a body mass index (BMI) <= 25 kg/m2 were analysed. We defined NWO as BMI <= 25 kg/m2 and body fat percentage >= 25% in men and >= 37% in women. Working patterns were classified into "daytime," "other than daytime," and "shift." Multivariable logistic regression analysis was performed to evaluate the relationship between shift work and NWO.Results: Shift work was associated with higher odds of NWO than daytime work (adjusted odds ratio [aOR], 1.47; 95% confidence interval [CI], 1.04 to 2.09) and night/evening work (aOR, 1.87; 95% CI, 1.11 to 3.14) after adjustment for type of work, working hours, age, sex, BMI, 25-hydroxyvitamin D levels, homeostatic model assessment for insulin resistance, and other sociodemographic factors. In subgroup analyses, the association between shift work and NWO was more robust in those aged >= 60 years and those working >= 56 hours/week.Conclusion: Shift work was associated with NWO in community-dwelling Korean adults, independent of age, sex, BMI, and other covariates.