Different associations of stay-at-home exposure with changes in body mass index and cardiometabolic factors depending on occupational physical activity: a longitudinal quasi-experimental design.

OBJECTIVES: To quantify the short-term impact of an unexpected stay-at-home exposure, caused by a shipment suspension, on body mass index (BMI) and cardiometabolic markers among employees with different levels of occupational physical activity. METHODS: Health-check records from 8307 workers at a large Japanese automobile manufacturer were linked to company attendance data covering a shipment suspension (January to April 2024). An interrupted time-series assessed BMI trajectories before, during, and after the halt. Among 614 employees who underwent an additional examination in April 2024, mixed-effects models related the duration of stay-at-home to changes in BMI and blood pressure within low-, medium-, and high-intensity job categories. RESULTS: Compared with pre-halt trends, medium-intensity and high-intensity workers showed significant level rises in BMI (0.96 kg/m2; 95% CI, 0.56-1.36; and 0.64 kg/m2; 95% CI, 0.24-1.04, respectively) at the onset of the suspension. Mixed-effects analyses showed a positive dose-response between the duration of stay-at-home and BMI gain in high-intensity jobs (0.47 kg/m2 per 20% absent days; 95% CI, 0.37-0.58). Per 20% of scheduled workdays absent, systolic blood pressure was higher in the medium- and high-intensity groups. No significant effects were observed among sedentary workers. CONCLUSIONS: Employees whose daily energy expenditure relies on job-related physical activity are especially susceptible to weight gain and blood pressure elevations during forced work interruptions. Business continuity plans should embed tailored countermeasures-such as structured exercise programs and phased returns to on-site duties-to safeguard metabolic health during future operational disruptions.