Exercise could have final say on fatty livers, study finds

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Fitness may be a more important clinical endpoint for improvement in patients with fatty liver diseases during exercise trials, rather than weight loss, according to a new study published in the journal Alimentary Pharmacology and Therapeutics.

For the study, the researchers used repeat biopsies in MAFLD patients during an exercise-only intervention. Only two previous studies have been conducted using repeat biopsies in exercise-only trials, but these studies had significant methodological limitations. These studies used low-intensity resistance exercise and lacked exercise supervision, which may have led to non-significant changes on liver biopsy outcomes. This study is also the first to relate improvements on liver biopsies with improvements in fitness, suggesting a potential interrelationship between the two outcomes.

Metabolic associated fatty liver disease (MAFLD) is a condition characterized by a buildup of fat in the liver. The liver is central to a suite of vital processes in the body including digestion, blood clotting, and energy production.

If left untreated, MAFLD can lead to serious complications like liver fibrosis, cirrhosis, liver failure, and liver cancer, as well as cardiovascular and metabolic issues. Risk factors for developing MAFLD include type 2 diabetes and obesity. The global estimated prevalence of MAFLD is 25 percent, making it the leading cause of chronic liver disease worldwide, and is quickly becoming the leading cause of cirrhosis and liver cancer in liver transplant candidates in the western world.

Treatment has been a combination of prescribed weight loss and physical activity, with a weight loss target of 7-10 percent being the primary treatment endpoint. There is some evidence that exercise training alone without significant weight loss can reduce liver fat content, assessed using non-invasive methodologies such as transient elastography and ultrasound, in MAFLD patients. However, the independent effects of exercise alone on biopsy-measured outcomes have been unknown.

The study found that increased fitness, the result of aerobic exercise participation, may be a more important clinical endpoint for improvement in MAFLD patients during exercise trials, rather than weight loss.

The findings demonstrated significant improvements in biopsy-measured liver outcomes in a MAFLD cohort following an exercise-only intervention, without clinically significant weight loss. The study also demonstrates that improvements in biopsy-measured liver outcomes were significantly related to improvements in fitness levels. The study also found however, that when patients were followed up longitudinally, none of the benefits of the exercise intervention were sustained.

There are little to no exercise referral systems in place within hospital departments and throughout the healthcare system, the researchers said. A systems-based approach whereby clinicians can refer patients to exercise specialists in the community is required for long-term benefits of exercise to be sustained.