Background and Aims: Previous studies have shown that greater aerobic fitness is associated with significantly lower levels of central obesity for a given BMI in comparison with low aerobic fitness. Recent studies have shown that not only aerobic fitness but also muscle strength plays a role in the prevention and management of central obesity. However, no studies have previously investigated the combined association of aerobic fitness and muscle strength with central adiposity for a given BMI. The purpose of this study was to test the hypothesis that, for a given BMI, Japanese middle-aged men with high aerobic fitness and muscle strength have a lower degree of central adiposity in comparison with men with low aerobic fitness and/or muscle strength.
Methods: The subjects included 1,662 healthy men aged 20-64 years who underwent a physical fitness test from June 2002 to April 2006 at Citizen’s Health Plaza Health Promotion Center. Aerobic fitness was assessed using a 20-m shuttle run test. Muscle strength was assessed by grip strength per body weight. Height and weight were measured using a stadiometer and standard physician’s scale and were used to calculate BMI (weight in kg per height in m2). Central adiposity was assessed with waist circumference (WC). WC was measured to the nearest 0.1 cm at the point of a noticeable waist with a flexible anthropometric tape. Aerobic fitness and muscle strength were used to split subjects into a HIGH (upper 2 quintiles) and LOW (lower 2 quintiles) group. Differences in the relationship between the BMI and WC among the HIGH and LOW groups were tested using general linear models, including age as a covariate.
Results: For a given BMI and muscle strength, the HIGH-aerobic fitness group had a significantly lower WC than the LOW-aerobic fitness group. For a given BMI and aerobic fitness, the HIGH-muscle strength group had a significantly lower WC than the LOW-muscle strength group. The difference between the HIGH-muscle strength group and the LOW-muscle strength group increased with increasing BMI. For a given BMI, the HIGH-aerobic fitness and muscle strength group (Group A) had a significantly lower WC than the HIGH-aerobic fitness and LOW-muscle strength group (Group B), LOW-aerobic fitness group and HIGH-muscle strength group (Group C) and LOW-aerobic fitness and muscle strength group (Group D). Group B and Group C had a significantly lower WC than Group D. No significant difference was observed between Group B and Group C.
Conclusions: A high degree of aerobic fitness and muscle strength is associated with lower levels of central adiposity for a given BMI in comparison with low aerobic fitness and/or muscle strength. This finding suggests that increasing aerobic fitness and muscle strength is important to prevent and reduce obesity-related health risks independent of a corresponding reduction in body weight.