Poor Fitness Associated with Fatty Liver Disease

By John Gever, Staff Writer
SAN FRANCISCO, March 25 -- Non-alcoholic fatty liver disease might respond well to regular moderate exercise, researchers here said.
Disease severity was significantly associated with poorer cardiorespiratory fitness in 37 patients with biopsy-confirmed fatty liver disease, reported Joanne Krasnoff, Ph.D., of the University of California San Francisco, and colleagues, online in Hepatology.
The study could not nail down a cause-and-effect relationship, but Dr. Krasnoff and colleagues said it was plausible that improved fitness would slow progression of fatty liver disease.
"It would appear rational and prudent for healthcare providers to recommend exercise training to improve health-related fitness as an integral role in the care of patients with non-alcoholic fatty liver disease," they wrote.
Non-alcoholic fatty liver disease is the most common cause of elevated liver enzymes in adults, with an estimated U.S. prevalence of 25%. It is generally considered to be the liver manifestation of metabolic syndrome.
Dr. Krasnoff and colleagues classified disease severity in the 37 patients by steatosis (mild, moderate, severe), fibrosis stage (stage 1 versus stage 2 or 3), necroinflammatory activity (Non-Alcoholic Fatty Liver Disease Activity Score up to 4 versus 5 or greater) and diagnosis of non-alcoholic steatohepatitis by standard criteria.
Thirty patients were diagnosed with non-alcoholic steatohepatitis. Fifteen had non-alcoholic fatty liver disease scores of 4 or less.
Patients underwent treadmill testing with cardiorespiratory fitness measured by peak VO2. Muscle strength was measured in the quadriceps with an isokinetic testing device.
Participants also reported current and 10-year average physical activity and were classified as active, somewhat active, and inactive.
Dr. Krasnoff and colleagues found few differences in these measures among the steatosis and fibrosis severity groups.
But increasing non-alcoholic fatty liver disease activity and the presence of non-alcoholic steatohepatitis were significantly associated with lower peak VO2.
Among patients with disease activity scores of 4 or less, mean peak VO2 was 30.4 mL/kg/min, compared with 24.4 mL/kg/min among those with scores of at least 5 (P=0.013).
Patients with a diagnosis of non-alcoholic steatohepatitis had a mean peak VO2 level of 25.1 mL/kg/min, versus 34.0 mL/kg/min for those without the diagnosis (P=0.048).
Moreover, the whole sample showed generally poorer cardiorespiratory fitness, muscle strength, body composition, and physical activity levels compared to the general population.
For example, about 84% of the participants had a body mass index greater than 25 and all but one patient had body fat percentages substantially higher than recommended for their age and gender. These problems with body composition put the patients at risk for cardiovascular disease and diabetes, Dr. Krasnoff and colleagues said.
Some 19% of patients were classified as active and 62% were somewhat active.
Mean peak torque in the quadriceps per unit of body weight was 37% (SD 10.7%), well below the normal values of 58% for women and 77% for men.
The researchers said this was the first study to compare health-related fitness and activity in patients with confirmed non-alcoholic fatty liver disease using objective, validated instruments. In general, the findings were consistent with other research in non-alcoholic fatty liver disease and metabolic syndrome, they said.
Dr. Krasnoff and colleagues wrote that their results raise a provocative cause-or-effect question: "Does cardiorespiratory fitness attenuate non-alcoholic fatty liver disease or does increasing non-alcoholic fatty liver disease severity result in a decline in cardiorespiratory fitness?"
They did not have a definitive answer, but suggested that acting on the former theory would probably be helpful.
"Lifestyle interventions to improve health-related fitness and physical activity may be beneficial in reducing the associated risk factors and preventing progression of non-alcoholic fatty liver disease," they wrote.
Current management guidelines include recommendations on diet and weight reduction, but make no mention of fitness assessment or specific exercise targets, Dr. Krasnoff and colleagues said.
They concluded that to determine a defined therapeutic role for exercise intervention, future studies should include a randomized controlled trial of exercise training that is well defined, monitored, and precisely quantified to elucidate the direct effects on non-alcoholic fatty liver disease histopathology.
The study was funded by the National Institutes of Health.
The authors reported no potential conflicts of interest.
Primary source: HepatologySource reference:Krasnoff J, et al "Health-related fitness and physical activity in patients with nonalcoholic fatty liver disease" Hepatology 2008; DOI: 10.1002/hep.22137.