Exercise can help people with an increasingly common type of liver disease improve their health, even if they don’t lose weight, a study shows.

A related study shows that people with this condition, known as non-alcoholic fatty liver disease (NAFLD), may want to cut down on cholesterol and protein.

Both studies are published in the medical journal Hepatology.

NAFLD is now the most widespread type of liver disease in the developed world, Dr. Alexis St. George of the University of Sydney, Australia, and colleagues note in their report. People with NAFLD have high levels of liver enzymes, indicating damage to the liver; fat bellies; and insulin resistance. NAFLD can progress to cirrhosis, an irreversible condition in which scar tissue replaces healthy liver tissue.

While increasing physical activity and eating healthier are currently the main recommendations for treating NAFLD, the researchers note, it’s still not clear whether becoming more active and boosting fitness might have benefits for NAFLD patients, independent of weight loss.

To investigate, they assigned 141 people to an exercise intervention including three individualized counseling sessions; six counseling sessions; or a control group who received just one counseling session at the study’s outset. Sessions happened every two weeks for the exercise groups.

Counselors encouraged exercise group participants to get at least 150 minutes of moderate-intensity physical activity to maintain their health, and 200 minutes weekly if they wanted to lose weight. Walking was the exercise most frequently recommended.

Three months after the study began, the exercise group participants were nine times more likely than control group participants to have boosted their exercise time by at least an hour a week. Even if the people who upped their exercise by at least an hour didn’t lose weight, they did whittle their waists. Adding this much activity also cut liver enzyme levels, while increasing activity even more didn’t produce additional reductions in liver enzymes.

“The reason for this is unclear, but we hypothesize that the threshold for change in liver enzymes may be so low that even a slight increase in physical activity is sufficient to improve liver tests,” St. George and colleagues suggest.

People who became fitter during the course of the study also showed greater improvement in LDL cholesterol levels, insulin resistance, and other key measurements of metabolic health than those whose fitness levels didn’t change - or worsened. Improvement was most dramatic for people with poor fitness at the study’s outset.

In the related study, Dr. George N. Ioannou of the University of Washington in Seattle and colleagues looked into the relationship between diet and risk of developing cirrhosis or liver cancer in 9,221 people aged 25 to 74 followed for more than 13 years as part of the National Health and Nutrition Examination Survey.

People who ate the most protein were at greater risk for being hospitalized for cirrhosis or liver cancer or dying from either condition, while high carbohydrate consumption was linked to a lower risk of developing or dying from either disease. Overall fat intake wasn’t related to liver disease risk or mortality, but cholesterol consumption was, although a person’s blood cholesterol levels didn’t relate to their liver disease risk.

“Our study raises the possibility that dietary factors may be important, modifiable and hitherto unrecognized determinants of liver disease progression,” Ioannou and his colleagues conclude.

SOURCE: Hepatology, July 2009.