Nonalcoholic fatty liver disease (NAFLD) has been referred to as the hepatic manifestation of the metabolic syndrome. There is a lower prevalence of metabolic syndrome in individuals with higher health-related fitness (HRF) and physical activity (PA) participation. The relationship between NAFLD severity and HRF or PA is unknown. Our aim was to compare measures of HRF and PA in patients with a histological spectrum of NAFLD severity. Thirty-seven patients with liver biopsy-confirmed NAFLD (18 women/19 men; age = 45.9 +/- 12.7 years) completed assessment of cardiorespiratory fitness (CRF, VO(2peak)), muscle strength (quadriceps peak torque), body composition (%fat), and PA (current and historical questionnaire). Liver histology was used to classify severity by steatosis (mild, moderate, severe), fibrosis stage (stage 1 versus stage 2/3), necroinflammatory activity (NAFLD Activity Score; <or=4 NAS1 versus >or=5 NAS2) and diagnosis of NASH by Brunt criteria (NASH versus NotNASH). Analysis of variance and independent t tests were used to determine the differences among groups. Fewer than 20% of patients met recommended guidelines for PA, and 97.3% were classified at increased risk of morbidity and mortality by %fat. No differences were detected in VO(2peak) (x = 26.8 +/- 7.4 mL/g/min) or %fat (x = 38.6 +/- 8.2%) among the steatosis or fibrosis groups. Peak VO(2) was significantly higher in NAS1 versus NAS2 (30.4 +/- 8.2 versus 24.4 +/- 5.7 mL/kg/min, P = 0.013) and NotNASH versus NASH (34.0 +/- 9.5 versus 25.1 +/- 5.7 mL/kg/min, P = 0.048).
Conclusion: Patients with NAFLD of differing histological severity have suboptimal HRF. Lifestyle interventions to improve HRF and PA may be beneficial in reducing the associated risk factors and preventing progression of NAFLD.