Mediating role of metabolic factors in the association between dietary habits and the onset of type 2 diabetes: a population-based Panasonic cohort study 19

Introduction: Diabetes mellitus is involved in the development of various diseases, including microvascular and macrovascular complications, infections, osteoporosis and dementia. This study aimed to evaluate the mediating role of obesity or metabolic abnormalities (hypertension, dyslipidaemia) in causal pathways between dietary habits (fast eating, skipping breakfast) and developing type 2 diabetes. Research design and methods: A retrospective cohort study was conducted using health examination data from employees of Panasonic Corporation in Japan. Information on participants' dietary habits, metabolic factors and the onset of diabetes was collected. Cox regression-based causal mediation analyses were performed to assess associations among dietary habits, metabolic factors and diabetes development. Results: Among 155 963 participants, fast eating (HR 1.93, 95% CI 1.73 to 2.14) and skipping breakfast (HR 1.31, 95% CI 1.24 to 1.37) were associated with increased onset of type 2 diabetes within 13 years. Fast eating showed a strong association with diabetes risk mediated through body mass index (BMI) (proportion mediated 0.73, 95% CI 0.65 to 0.85) while skipping breakfast showed a direct association with diabetes risk not mediated through BMI (proportion mediated 0.10, 95% CI 0.07 to 0.14). Both dietary habits exhibited small mediating effects through hypertension or dyslipidaemia. Conclusions: Fast eating increases diabetes risk, primarily through BMI, whereas skipping breakfast poses a risk not through BMI. These findings suggest a mechanism by which dietary habits affect glucose metabolism.