Exercise training has been shown to have positive effects on liver function in overweight adults or those with fatty liver disease, according to new research by the University of New England.
Associate Professor Neil Smart from the School of Science and Technology said the focus of this current work, was to find out which exercise programme characteristics generated the best results.
“What we found is that you can improve levels of fat in the liver but you need to burn 10 000 kcalories before you start to see optimal benefits. That is about 20-25 hours of exercise at moderate intensity, so if you work at a higher intensity you will get quicker results” said Assoc/Prof. Smart.
The study, Effect of exercise training on liver function in adults who are overweight or exhibit fatty liver disease: a systematic review and meta-analysis, has been published in the British Journal of Sports Medicine.
The UNE research team looked at 21 randomised controlled trials involving 1530 participants.
“We searched for all the randomised trials that have been published in that area and extracted data from each of them. A lot of the studies are small, so on their own they don’t mean much, but by pulling this data together we have made a much bigger sample size.”
Associate Professor Smart says the work analysed the effects of exercise training with or without dietary intervention.
“Our analysis suggested the intrahepatic fat is reduced with exercise training in as little as 4 weeks. It seems that the benefits kick in once someone has expended about 10,000 Kcals via exercise, so intuitively we might assume that if one exercises at higher-intensity then they will access the health benefits sooner.”
Numerous published studies show that some people lose motivation with moderate intensity exercise, as the benefits take longer to reveal themselves.
Alternatively, recent work on high intensity exercise shows a variety of benefits relating to metabolic disorders with very low volumes of activity.
“I should caution though that some exercise experts remain reticent about the safety of high intensity exercise, but this view is currently intuitive, rather than definitively supported by an evidence base showing high intensity activity equals an increased risk of serious events. In fact the landmark 1993 Determinants of Myocardial Infarction Onset Study clearly shows that the more weekly bouts of vigorous activity a person does, the lower their risk of exertional heart attack,” said Assoc/Prof. Smart.
“So our analyses suggests that it is calorie burning that elicits reductions in liver fat, reduced fat storage, possibly reduced liver enzymes and the sum of all of this is improved glycaemic control.”
Assoc/Prof. Smart says the varied study interventions still make it difficult to separate the relative effects of diet and exercise on the liver function.
“Half the included studies had some diet treatment as well as exercise so it was difficult to separate diet from exercise. Diet will play a role, so if you can reduce your calorie intake you will possibly see more benefit than if you don’t.”
The research has also shown that blood levels of liver enzymes are considered by some to be unreliable measures of liver function, liver biopsy seems to be the gold standard. Whatever method used in clinical practice, it should be noted that it maybe redundant to reassess liver function before three months of adherent exercise training with or without calorie intake restriction.