Purpose: Fatty liver is an expanding health concern associated with metabolic disturbances and increased risk of cardiovascular disease. Experimental studies in animals have shown associations between fatty liver and cardiorespiratory fitness but limited data exist in humans. The aim of this study was to analyze the links between cardiorespiratory fitness and fatty liver in a population-based sample of adults.
Methods: Participants were 463 adults (48% men) from the Cardiovascular Risk in Young Finns Study. Cardiorespiratory fitness was measured with a cycle ergometer exercise test as peak oxygen uptake (V˙O2peak [mL·kg·min]) in 2008 to 2009. Hepatic ultrasonographic imaging was performed in 2011 to determine fatty liver.
Results: Cardiorespiratory fitness was associated with lower risk of fatty liver (1 mL·kg·min increase in V˙O2peak: risk ratio, 0.90; 95% confidence interval, 0.88-0.93, P < 0.0001; adjusted for age and sex). This association remained significant after further adjustments with physical activity, adiposity, smoking, alcohol consumption, serum lipids, insulin, glucose, and C-reactive protein. Participants who were obese (waist circumference, >80 cm in women and >94 cm in men) but fit (V˙O2peak in the upper age- and sex-specific median) had lower prevalence of fatty liver than participants who were obese and unfit (below median), (11.7% vs 34.8%, P = 0.0003).
Conclusions: In a population-based sample of adults, cardiorespiratory fitness is strongly, inversely and independently related with the risk of fatty liver. Importantly, the association is evident also among obese.