Background: Obesity in middle age is a well-known risk factor for the development of type 2 diabetes mellitus. However, the importance of weight and weight gain at younger ages is less certain.
Objective: To determine the relationship of body weight patterns from 20 to 49 years of age with the subsequent risk for type 2 diabetes mellitus.
Setting: An ongoing longitudinal study of former medical students.
Participants: Nine hundred sixteen white men without diabetes at 50 years of age.
Measurements: Weight and height measured in medical school, then assessed by mailed questionnaire to 49 years of age.
Main outcome: Incident type 2 diabetes mellitus based on physician self-report.
Results: During 14 255 person-years of follow-up, there were 35 incident cases of type 2 diabetes mellitus (2.5 per 1000 person-years). After simultaneous adjustment for age, physical activity, lifetime maternal history of diabetes, and smoking, body mass indexes (BMIs; calculated as weight in kilograms divided by the square of height in meters) at 25, 35, and 45 years of age were all strongly associated with diabetes risk (relative risks for overweight [BMI> or =25.0] vs. not overweight, >3.0; all Ps<.05), as were maximum and average BMI to 49 years of age. The relationship of BMI at 25 years of age to diabetes risk was substantially attenuated by adjustment for BMI at 45 years of age and average BMI, but was independent of weight change, weight variability, or maximum BMI.
Conclusion: In men, overweight at 25 years of age strongly predicts diabetes risk in middle age, largely through its association with overweight at 45 years of age and high average BMI to 49 years of age.