Obesity as a mediator of the inf luence of cardiorespiratory fitness on cardiometabolic risk: A mediation analysis

Abstract

OBJECTIVE The relationship between cardiorespiratory fitness (CRF) andmetabolic syndrome (MetS) is well known, although the extent to which body weight may act as a confounder ormediator in this relationship is uncertain. The aimof this study was to examinewhether the association between CRF and cardiometabolic risk factors is mediated by BMI. RESEARCH DESIGN AND METHODS A cross-sectional study including 1,158 schoolchildren aged 8-11 years from the province of Cuenca, Spain, was undertaken. We measured height, weight, waist circumference (WC), blood pressure, fasting plasma lipid profile and insulin, and CRF (20-m shuttle run test). A validated cardiometabolic risk index was estimated by summing standardized z scores of WC, log triglyceride-to-HDL cholesterol ratio (TG/HDL-c), mean arterial pressure (MAP), and log fasting insulin. To assess whether the association between CRF and cardiometabolic risk was mediated by BMI, linear regression models were fitted according to Baron and Kenny procedures for mediation analysis. RESULTS In girls, BMI acts as a full mediator in the relationship between CRF and cardiometabolic risk factors, with the exception of log TG/HDL-c ratio. In boys, BMI acts as a fullmediator in the relationship between CRF and both log TG/HDL-c ratio and MAP, and as a partial mediator in the relationship between CRF and cardiometabolic risk factors. CONCLUSIONS BMI mediates the association between CRF and MetS in schoolchildren. Overall, good levels of CRF are associated with lower cardiometabolic risk, particularly when accompanied by weight reduction.© 2014 by the American Diabetes Association.