Reuters Health Information (2011-07-15): Lifestyle changes pay off in non-alcoholic fatty liver disease
Lifestyle changes pay off in non-alcoholic fatty liver disease
Last Updated: 2011-07-15 11:16:28 -0400 (Reuters Health)
NEW YORK (Reuters Health) - Weight loss or increased physical activity "consistently" reduce liver fat and improve glucose control and insulin sensitivity in patients with non-alcoholic fatty liver disease (NAFLD), according to a systematic review of published studies.
"Limited data also suggest that lifestyle interventions may hold benefits for histopathology," Dr. Michael Trenell and colleagues from Newcastle University, Newcastle upon Tyne, United Kingdom report in a paper in the Journal of Hepatology, available online now.
NAFLD, they note in their paper, is a "serious and growing clinical problem" affecting an estimated 20% to 33% of the adult population, depending on criteria and country.
Diet and physical activity are often recommended in patients with NAFLD, despite a lack of systematic evaluations of the efficacy of this approach.
This prompted Dr. Trenell and colleagues to search Medline, Scopus, and the Cochrane Controlled Trials Register for studies looking at the effect of diet, physical activity, and/or exercise modification in adults with NAFLD.
"The outcome markers of interest were indicators of steatosis, histological evidence of inflammation and fibrosis, and glucose control/insulin sensitivity," they wrote in their paper.
The analysis included 23 studies. Seven had control groups, but only six were randomized. Eleven groups received diet-only interventions, two received exercise-only, and 19 received diet and physical activity/exercise. The interventions lasted from one to six months. The physical activity interventions consisted largely of moderate intensity aerobic activity.
Overall, the studies showed that a range of lifestyle modifications are effective in reducing elevated intrahepatic triacyglycerol concentration (IHTAG) - the first step in the development of steatohepatitis, liver fibrosis, liver cirrhosis and hepatocellular carcinoma.
Overall, reductions in body weight averaged 4% to 14% and resulted in statistically significant IHTAG reductions of 35% to 81%. The magnitude of change correlated strongly with the amount of weight lost.
The reviewed studies also "consistently showed reductions in liver fat and/or liver aminotransferase concentration," the investigators say, "with the strongest correlation being with weight reduction."
In most of the studies, glucose control and/or insulin sensitivity improved after lifestyle intervention.
Five studies reported changes in histopathology and all showed a trend toward decreased inflammation. In two studies, this was statistically significant, the researchers report. "Changes in fibrosis were less consistent with only one study showing a significant reduction," they add.
There was, however, considerable heterogeneity across studies in specific interventions and assessment methods employed and diagnostic criteria for NAFLD applied.
In addition, monitoring of adherence to diet or exercise was often limited, and no study employed objective measures of physical activity such as accelerometers. Instead, they all used questionnaires. Dietary assessments were not reported in enough detail to assess likely accuracy.
"Given the clinical impact of NAFLD and the lack of therapies for its management, developing effective, reproducible lifestyle interventions is crucial," the investigators conclude.
Unfortunately, published studies to date looking at lifestyle interventions in adults with NALFD "do not allow clear differentiation of the effects of physical activity relative to diet, or the importance of diet composition," they write.
They suggest future studies employ "accurate methods to establish the most effective means of producing a sustained reduction in liver fat, necroinflammation, and, if possible, fibrosis and report their interventions, including objective indicators of adherence, in sufficient detail to be readily translatable to clinical practice.
J Hepatology 2011.