Association between Cardiorespiratory Fitness, Muscle Strength, and Non-Alcoholic Fatty Liver Disease in Middle-Aged Men

Abstract

Background: Nonalcoholic fatty liver disease (NAFLD) occurs when more than 5% of fat accumulates in the liver parenchyma without excess alcohol consumption. The objective of this study is to investigated the association between cardiorespiratory fitness (CRF), muscle strength (MS), and NAFLD. Methods: The subjects of this study were 1325 males aged 40–50 who had visited the National Fitness Center located in the Republic of Korea from 2017 to 2019. Abdominal ultrasonography testing was used for NAFLD diagnosis. For CRF, an MS test was used to measure maximal oxygen intake and grip strength. CRF and MS were classified into 3 quartiles (high, middle, low-level). In addition, both the CRF level and MS level were classified into 9 quadrants. Results: With confounding factors (age, body mass index, exercise, smoking) controlled, there was no relative risk of NAFLD between middle and high levels of CRF (95% CI, 0.92–2.17). However, the relative risk of NAFLD in the case of low-level CRF was 1.63-fold (95% CI, 1.03–2.60, p < 0.05) higher than that in the case of high-level CRF. Meanwhile, there was no significant difference between middle-level MS (95% CI, 0.68–1.65) and high-level MS (95% CI, 0.84–1.99) in terms of NAFLD relative risk. The NAFLD relative risk in the case of low-level CRF/MS was 2.27-fold (95% CI, 0.94–1.99, p < 0.05) higher than that of high-level CRF/MS. Conclusions: The low CRF and MS group had a higher risk of NAFLD compared with the high CRF and MS group. Maintenance of high CRF and MS may be beneficial in preventing NAFLD.