Holtermann A, et al. - Researchers planned this study to examine whether the effect of cardiorespiratory fitness (CRF) on diabetes risk was similar across levels of fatness among healthy men. Among obese men, high CRF had a stronger protective effect on diabetes than among normal weight men. Thus, this study supported that sustainable weight loss needed to be an integrated part of the fitness-improving physical activity for preventing diabetes among the obese.

• The researchers included 4,988 middle-aged Caucasian employed men free of cardiovascular disease, diabetes, and cancer from the Copenhagen Male Study starting in 1970-71.
• They assessed CRF using a sub-maximal bicycle ergometer test and measured body mass index (BMI) by height and weight.
• They estimated their interaction and stratified associations with diabetes incidence in multivariable Cox-models including conventional risk factors and social class.
• Through a national register, diabetes incidence was evaluated.

• 518 (10.4%) incident cases of diabetes occurred during 44 years of follow-up.
• The obese had a significantly higher risk of diabetes than the normal weight men (Hazard Ratio (HR):4.89; 95%CI: 3.62-6.61) and CRF was significantly inversely correlated with diabetes (HR:0.86; 95%CI:0.75-0.98 per 10-unit increase in ml/kg/min1 CRF) in the multi-adjusted model.
• The researchers found a significant multi-adjusted interaction between CRF, BMI and diabetes (p=0.009).
• The stratified multi-adjusted analyses on BMI demonstrated a significantly stronger, reduced risk of diabetes per 10-unit increase in ml/kg/min¹ of CRF among the obese (HR:0.58; CI:0.38-0.89).
• However, it showed a weaker association among overweight (HR:0.86; CI:0.71-1.03) and normal weight (HR:0.97; CI:0.76-1.23).