Objective: The aim of this study was to establish a causal relationship between excess body weight and the onset of diabetes in a retrospective cohort study.
Methods: This 10-year observational cohort study investigated 969 men and 585 women (23 to 80 years of age), who underwent voluntary complete medical check-ups and an annual 75-g oral glucose tolerance test (75 g-OGTT). Participants with fasting plasma glucose ≥126 mg/dL, 2-h glucose level in a 75 g-OGTT ≥200 mg/dL and/or received medical treatment for type 2 diabetes during the previous year were considered as new-onset diabetics. We assessed the independent contribution of increased BMI to the risk of developing type 2 diabetes with Cox proportional hazard model.
Result: During the follow-up period, we diagnosed 86 men and 49 women with new-onset type 2 diabetes. In the Cox proportional hazards model, the risk of diabetes mellitus increased with increasing BMI, even after adjusting for age, sex, blood pressure, metabolic profiles, and insulin resistance. In the final model, setting BMI less than 25 as a reference group, the Hazard ratios for diabetes mellitus was 3.12 for those with a BMI of 25-27.4 and it was increased to 3.80 for participants with a BMI of 27.5 or higher.
Conclusion: Overweight/obesity (high BMI) is an independent and dose-dependent risk factor for type 2 diabetes in overweight Japanese patients. Our results confirmed the usefulness of BMI as a classic parameter, and the importance of lifestyle modification and better management among people with overweight/obesity for prevention of type 2 diabetes mellitus.