Association of Cardiorespiratory Fitness and Overweight with Risk of Type 2 Diabetes in Japanese Men

OBJECTIVE Existing evidence is limited on what extent fitness can counterbalance type 2 diabetes mellitus (T2DM) risk associated with obesity. We investigated the joint association of weight status and estimated VO2max, a marker of fitness, with the risk of developing T2DM among Japanese men using haemoglobin A1c and fasting glucose criterion. METHODS The present study included 3,523 male employees aged 18-61 years without diabetes who provided health check-up and fitness data in Japan in 2003-2005. We calculated hazard ratios and 95% confidence intervals for incident diabetes using the Cox regression model. RESULTS During a mean follow-up of 6.0 years, 199 men developed diabetes. Multivariable-adjusted hazard ratios (95% confidence interval) of diabetes were 1.00 (reference), 1.44 (1.01-2.07), and 1.48 (1.03-2.13) for the highest through the lowest tertile of fitness (P for trend  = 0.04). Additional adjustment for body mass index largely attenuated the association of fitness with diabetes. Joint analysis showed that adjusted hazard ratios of diabetes were 1.00, 1.32, 2.94, and 1.83 in normal weight high-fit men, normal weight low-fit men, overweight high-fit men, and overweight low-fit men, respectively. CONCLUSION The results suggest that weight control is more important than fitness in prevention of type 2 diabetes in Japanese men.