title: Physical activity recommendations, exercise intensity, and histological severity of nonalcoholic fatty liver disease.
abstract: OBJECTIVE
  Factors that determine disease severity in nonalcoholic fatty liver disease (NAFLD) are unclear, but exercise is a recommended treatment. We evaluated the association between physical activity intensity and histological severity of NAFLD.
  
  
  METHODS
  We conducted a retrospective analysis of adults with biopsy-proven NAFLD enrolled in the NASH CRN (Nonalcoholic Steatohepatitis Clinical Research Network). Using self-reported time spent in physical activity, we classified participants as inactive or as meeting the US guidelines for either moderate or vigorous exercise. Histology was reviewed by a central pathology committee. Frequency and odds of steatohepatitis (NASH) and advanced fibrosis were compared between subjects who either met or did not meet exercise recommendations, and by the total amount of exercise per week.
  
  
  RESULTS
  A total of 813 adults (males=302, females=511) with NAFLD were included, with a mean age of 48 years. Neither moderate-intensity exercise nor total exercise per week was associated with NASH or stage of fibrosis. Meeting vigorous recommendations was associated with a decreased adjusted odds of having NASH (odds ratio (OR): 0.65 (0.43-0.98)). Doubling the recommended time spent in vigorous exercise, as is suggested for achieving additional health benefits, was associated with a decreased adjusted odds of advanced fibrosis (OR: 0.53 (0.29-0.97)).
  
  
  CONCLUSIONS
  These data support an association of vigorous but not moderate or total exercise with the severity of NAFLD. Optimal doses of exercise by duration and intensity for the prevention or treatment of NASH have not been established; however, intensity may be more important than duration or total volume.
authors.affiliation: Division of Gastroenterology, Hepatology, and Nutrition, Department of Pediatrics, University of California, San Diego, California 92103, USA.
authors.forename: Kristin D
authors.initials: KD
authors.lastname: Kistler
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: Brunt
authors.forename: Jeanne M
authors.initials: JM
authors.lastname: Clark
authors.forename: Anna Mae
authors.initials: AM
authors.lastname: Diehl
authors.forename: James F
authors.initials: JF
authors.lastname: Sallis
authors.forename: Jeffrey B
authors.initials: JB
authors.lastname: Schwimmer
mesh_terms: D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000097:blood; D001706:Biopsy; D015992:Body Mass Index; D003430:Cross-Sectional Studies; D015444:Exercise; D005234:Fatty Liver / Q000097:blood / Q000453:epidemiology / Q000473:pathology*; D005260:Female; D006801:Humans; D008099:Liver / Q000473:pathology*; D008103:Liver Cirrhosis / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D009043:Motor Activity; D065626:Non-alcoholic Fatty Liver Disease; D016017:Odds Ratio; D012189:Retrospective Studies; D012307:Risk Factors; D012720:Severity of Illness Index; D014481:United States / Q000453:epidemiology
chemical_list: D015415:Biomarkers