Preventive Cardiology
Fitness, Body Habitus, and the Risk of Incident Type 2 Diabetes Mellitus in Korean Men

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The relative contributions of cardiorespiratory fitness (CRF) and body habitus to predict incident type 2 diabetes mellitus (T2DM) remain unclear. We prospectively investigated the relation of CRF and body habitus on the risk of developing T2DM in men. Participants included 3,770 apparently healthy men who initially presented without baseline evidence of diabetes, cardiovascular disease, and hypertension. Participants were divided into 3 groups as normal weight (18.5 to 24.9 kg/m2), obese I (25.0 to 29.9 kg/m2), and obese II (≥30.0 kg/m2). CRF was directly measured by peak oxygen uptake (VO2peak) and categorized into unfit and fit cohorts based on the median value of age-specific VO2peak. Diabetes was defined as a glycated hemoglobin >6.5% and/or a fasting glucose >126 mg/dl at baseline and follow-up examinations. During a median follow-up of 5 years, 170 men (4.5%) developed diabetes. After adjusting for age and fasting glucose, the relative risk and 95% confidence interval (CI) for incident T2DM were 1.52 (95% CI 1.11 to 2.07) for obese I and 3.11 (95% CI 1.35 to 7.16) for obese II versus normal weight and 0.69 (95% CI 0.51 to 0.95) for fit versus unfit. However, these associations were no longer statistically significant after adjusting for potential confounders with VO2peak (1.32; 95% CI 0.96 to 1.83 for obese I and 1.61, 95% CI 0.64 to 4.06 for obese II vs normal weight) or body mass index (0.75, 95% CI 0.54 to 1.05 for fit vs unfit). In the joint analysis, obese-unfit men had 1.81 times (95% CI 1.22 to 2.69) greater risk of incident T2DM, but obese-fit men were not at increased risk of incident T2DM (0.95, 95% CI 0.57 to 1.58) compared with fit-normal weight men. In conclusion, these results suggest that both CRF and obesity predict the incidence of T2DM independent of potential confounders; however, CRF appears to attenuate the risk of developing diabetes in obese men.

Section snippets

Methods

Our study participants included 5,616 men who participated in 2 general health examinations from 1998 to 2009 at the Samsung Medical Center, Seoul, South Korea. Of these participants, men who had hypertension, T2DM, or a history of cardiovascular disease and those who were taking antihypertensive medications and/or oral hypoglycemic agents at baseline were excluded. Further exclusions included subjects whose relevant blood markers (glucose and glycated hemoglobin A1c) and CRF, determined during

Results

During a median follow-up of 5 years, 170 of the 3,770 men (4.5%) developed T2DM. Men who developed T2DM had greater age, BMI, alcohol consumption, glucose, triglycerides, and glycosylated hemoglobin (HbA1c) levels but lower HDL cholesterol and VO2peak (all p <0.05) at baseline compared with men who remained nondiabetics (Table 1). Table 2 summarizes the relative risks (RR) and 95% confidence interval (CI) of incident T2DM with specific reference to CRF and obesity. After adjusting for age and

Discussion

Our findings indicate that CRF and obesity were associated with a lower and higher risk of incident T2DM, respectively, and that these associations were mutually dependent. Thus, both improved fitness and reduction of body weight and fat stores should be encouraged to reduce the risk of developing diabetes. However, the novel finding from our study is that obese, unfit men had greater risk of incident T2DM compared with normal weight, fit men, whereas obese, fit men had a similar risk of

Disclosures

The authors have no conflicts of interest to declare.

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