The importance of cardiorespiratory fitness in obesity-related disease: a cross sectional-analysis

Background: Exercise-induced improvements in cardiorespiratory fitness (CRF) often coincide with improvements in insulin sensitivity and intrahepatic lipid content (IHL). The aim of this study was to examine the association between CRF, IHL, and insulin resistance in inactive adults with obesity and with or without type 2 diabetes, via cross-sectional design.Methods: CRF was determined via a graded exercise test. IHL was assessed via proton magnetic resonance spectroscopy ( 1 H-MRS) and insulin resistance was assessed via homeostatic model of insulin resistance (HOMA-IR). Participants were stratified into CRF quartiles and analysis of variance was employed to determine significant differences in IHL%, HOMA-IR and cardiometabolic outcomes between CRF quartiles. Results: Seventy-two adults (46% male) with a mean age of 49 ± 10 years, IHL of 8.37 ± 6.90%, and CRF of 21.52 ± 3.77 mL/kg/min participated in this study. CRF was inversely associated with IHL (r= -0.28, p=0.019) and HOMA-IR (r= -0.40, p<0.001). Participants with the lowest CRF had significantly higher IHL% and HOMA-IR than those with the highest CRF (+5.31%, p = 0.021; +2.50, p = 0.001, respectively). Participants with the lowest CRF also had significantly greater cardiovascular and inflammatory abnormalities than those with the highest CRF.Conclusion: CRF was inversely associated with IHL and HOMA-IR and participants with the highest levels of CRF had significantly lower cardiometabolic risk than those with the lowest levels of fitness. Improving CRF should remain a key therapeutic target for the management of obesity-related disease.