The association between cardiorespiratory fitness and NAFLD in overweight and obese adults

Introduction: Cardiorespiratory fitness (CRF) is a known independent risk factor for morbidity and mortality (1). Furthermore, CRF and obesity have been shown to be associated with impaired fasting glucose (IFG) and type 2 diabetes (T2D) by similar magnitudes (2). Nonalcoholic fatty liver disease (NAFLD) is also associated with IFG and T2D, and increases in CRF has been shown to mitigate IFG and insulin resistance. The primary aim of this study was to explore the association between CRF and NAFLD in inactive adults with overweight and obesity. A secondary aim was to examine the possible association between CRF and NAFLD independent of known demographic and anthropometric risk factors. Methods: CRF, IHL, and other demographic, anthropometric and biochemical risk factors were assessed in 67 inactive, overweight and obese adults with and without diabetes. CRF was measured via a graded exercise test (Lode Corival cycle ergometer). NAFLD was assessed by grading participants' liver fat concentration via proton magnetic spectroscopy (where a liver fat score >5.5% was classified as NAFLD positive). Bivariate regression and hierarchical multiple regression analyses were performed. RESULTS: CRF was not associated with NAFLD (p=0.49) nor liver fat concentration (p=0.09). CRF was associated with other cardiometabolic risk factors such as fasting blood glucose (p=0.02), fasting serum insulin (p=0.02) and systolic blood pressure (p=0.04), however these associations were not independent of BMI. Conclusion: Our findings showed that CRF was not associated with NAFLD in inactive, overweight and obese adults, with and without diabetes. Additional studies incorporating a greater variation in CRF are needed to further explore the relationship between CRF and liver fat.