Physical Activity May Benefit Patients With Nonalcoholic Fatty Liver Disease

Laurie Barclay, MD

July 21, 2009 — Physical activity may benefit patients with nonalcoholic fatty liver disease (NAFLD) independent of weight changes, according to the results of a study reported in the July issue of Hepatology.

"Nonalcoholic fatty liver disease, characterized by elevated liver enzymes, central obesity, and insulin resistance, is becoming increasingly prevalent," write Alexis St. George, PhD, from the University of Sydney and Westmead Hospital in Sydney, Australia. "The effects of changes in physical activity on the metabolic profile of this group have not been reported."

The investigators studied the effect at 3 months of a behavior change–based lifestyle intervention on physical activity and on the metabolic profile of 141 patients with NAFLD who were prospectively enrolled into either a low-intensity or moderate-intensity lifestyle intervention or to a control group. A validated reporting tool was used to measure physical activity, and the YMCA protocol on a cycle ergometer was used to determine physical fitness. All participants in the intervention groups received individualized counseling to increase physical activity.

Follow-up rate for the 3-month evaluation was 96%. Compared with participants in the control group, those in the moderate-intensity and low-intensity intervention groups were 9 times more likely to increase physical activity by at least 1 hour per week.

Compared with patients who were least active, those who improved or maintained their reported physical activity to more than 150 minutes per week and those who improved their objective levels of fitness had the greatest improvements in liver enzymes and other metabolic markers.

These benefits were independent of weight loss and were corroborated by an objective measure of fitness. With incremental increases in physical activity of more than 60 minutes per week, there was no dose-response effect on liver enzymes.

"Lifestyle counseling interventions are effective in improving physical activity behavior," the study authors write. "Maintaining or increasing physical activity provides health benefits for patients with fatty liver, independent of changes in weight."

Limitations of this study include lack of objective measures of change in physical activity.

"Improvements in physical activity can have positive effects on liver enzymes, insulin resistance, and other metabolic parameters in people with NAFLD," the study authors conclude. "This is a particularly important outcome, as liver fat has been shown to correlate independently with all risk factors of the metabolic syndrome....This study highlights the risk of remaining or becoming physically inactive (irrespective of whether weight loss is achieved) on metabolic parameters in patients with liver disease, and demonstrates the importance of physical activity for patients with NAFLD."

•Individual lifestyle counseling interventions are effective in improving physical activity behavior in patients with NAFLD. Participants in the moderate-intensity and low-intensity intervention groups were 9 times more likely than those in the control group to increase physical activity by at least 1 hour per week.
•Independent of weight changes, maintaining or increasing physical activity provides health benefits for patients with NAFLD, with improvements in liver enzymes and other metabolic markers. The underlying mechanism may be improved insulin resistance through positive changes in fatty acid metabolism in muscle.

Hepatology. 2009;50:68-76.