Higher Cardiorespiratory Fitness Is Associated With a Lower Burden of Metabolic Syndrome Traits: A Cross‐Sectional Analysis of 39 197 UK Adults

AIMS: To investigate associations of cardiorespiratory fitness (CRF) with metabolic syndrome (MetS) trait count, MetS prevalence and individual MetS traits in a large population-based cohort. MATERIALS AND METHODS: ; 31% female). CRF was estimated as peak oxygen uptake from submaximal treadmill or cycle ergometer protocols and analysed continuously and as sex- and mode-specific quintiles. MetS was defined using established criteria, with outcomes examined as trait count (0-5), presence (≥ 3 traits) and individual traits. Associations were assessed using negative binomial regression for trait count and Poisson regression for MetS presence. Models were sequentially adjusted for demographics (primary model), adiposity (BMI) and hepatic steatosis (fatty liver index [FLI]). RESULTS: higher CRF was associated with a 2.9% lower MetS trait count and 6.0% lower MetS prevalence (p < 0.001). Compared with the highest CRF quintile, the lowest quintile had a 2.4-fold higher MetS trait count and 5.4-fold higher MetS prevalence (p < 0.001). Associations persisted after BMI and FLI adjustment, although attenuated. Spline analyses demonstrated graded, non-linear inverse associations, steepest at lower CRF levels. Higher CRF was inversely associated with all individual MetS traits, strongest for central obesity. CONCLUSIONS: Higher CRF was associated with lower metabolic risk burden and MetS prevalence, which remained after adjustment for adiposity-related measures. These findings support the potential public health relevance of modest fitness improvements, particularly among the least fit adults, as a strategy that may help reduce MetS burden even when adiposity changes are limited.