Background and Purpose

Diabetes mellitus is a major cause of death and can lead to complications of cardiovascular disease. High physical activity (HPA) and normal weight play a role in reducing the risk of diabetes. This study analyzed the relative risk (RR) of diabetes according to obesity and physical activity using national health census data.

Methods

Nationwide health screening was performed for all adults every 2 years. Data from 5,590,120 men and 4,102,523 women, who were followed up for 10 years, were analyzed. Physical activity questionnaires about weekly exercise frequency were used to define low physical activity (LPA, 0–2 days), moderate physical activity (MPA, 3–5 days), and high physical activity (HPA, 6–7 days). Body mass index (BMI) ≤24.9 kg/m² was defined as normal, BMI 25.0–29.9 kg/m² was overweight, and BMI ≥30.0 kg/m² was obese. The RR was calculated using Cox analysis.

Results

Diabetes incidence rates were 14.8% in overweight men, 20.0% in men with obesity, 17.9% in over-weight women, and 22.7% in women with obesity. The RR increased by 2.5 times in men with obesity and 3.4 times in women with obesity as compared with that of individuals with a normal BMI. Among overweight and obese individuals, those with HPA had decreased risks of developing diabetes compared with those with LPA (adjusted relative risk [ARR] for overweight individuals: 0.976 for men and 0.966 for women; ARR for individuals with obesity: 0.936 for men and 0.931 for women).

Conclusion

A high BMI increases the risk of diabetes; however, as physical activity increases, the risk of diabetes decreases. In the overweight and obese groups, those with higher physical activity had a lower risk of developing diabetes.