Associations between cardiorespiratory fitness and the metabolic syndrome in British men.

Background: Age and body mass index (BMI) are positively associated with the development of the metabolic syndrome (MetS). Cardiorespiratory fitness (CRF) can attenuate BMI-related increases in prevalence of MetS, but the nature of this association across different age strata has not been fully investigated.

Aim: To identify the association between CRF and MetS prevalence across age strata (20-69 years) and determine whether associations are independent of BMI.

Methods: CRF was estimated from incremental treadmill exercise in British men attending preventative health screening. Participants were placed in four age strata (20-39, 40-49, 50-59 and 60-69 years) and classified as fit or unfit using age-related cut-offs. The presence of MetS was defined using the National Cholesterol Education Program Adult Treatment Panel III criteria.

Results: 9666 asymptomatic men (48.7±8.4 years) were enrolled. The prevalence of MetS was 25.5% in all men and ranged from 17.1% in those aged 20-39 years to 30.6% in those aged 60-69 years. Fit men's likelihood of meeting the criteria for MetS was half (OR=0.51, 95% CI 0.46 to 0.57) that of unfit men. The likelihood of MetS was 32-53% lower across age strata in fit, compared with unfit men. Adjustment for BMI attenuated the association, though it remained significant in men aged 20-49 years.

Conclusions: The cardiometabolic benefits of CRF are independent of BMI particularly in men <50 years. Public health messages should emphasise the important role of CRF alongside weight management for enhancing cardiometabolic health.