Physical Activity, Body Mass Index, and Diabetes Risk in Men: A Prospective Study

OBJECTIVE: Physical activity has been associated with lower diabetes risk, but several prospective studies among women found that activity only slightly attenuated the diabetes risk associated with high body mass index (BMI). We investigated the independent and joint associations between vigorous activity and BMI on diabetes risk in men. METHODS: This was a prospective cohort design within the Physicians' Health Study, using Cox proportional hazards models to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) of incident diabetes in 20,757 men without diabetes at baseline. Models were based on self-reported BMI and exercise frequency at baseline, first separately and then with a 6-category joint variable combining World Health Organization BMI category (normal/overweight/obese) with activity status (active/inactive) using weekly vigorous activity as the threshold. RESULTS: After a median follow-up of 23.1 years, there were 1836 cases of incident diabetes. Compared with active participants with normal BMIs, active but overweight and obese men had multivariable-adjusted HRs of 2.39 (95% CI, 2.11-2.71) and 6.22 (95% CI, 5.12-7.56). Inactive men with normal, overweight, or obese BMIs had multivariable-adjusted HRs of 1.41 (95% CI, 1.19-1.67), 3.14 (95% CI, 2.73-3.62), and 6.57 (95% CI, 5.25-8.21). CONCLUSION: Active men with normal and overweight BMIs had lower diabetes hazards than their inactive counterparts, but no difference by weekly activity was seen in obese men. Elevated BMI is a key driver of diabetes risk, with relatively modest attenuation by activity. Published by Elsevier Inc. The American Journal of Medicine (2009) 122, 1115-1121