Fatty liver disease commonly affects alcoholics and those who are overweight or diabetic. There are currently no treatments for this disease, aside from recommendations to exercise and make lifestyle changes. A recent review article summarizes the high science behind how exercise can improve fatty liver disease.
The liver is one of the most important organs in our body and has several important roles. It is responsible for detoxifying chemicals and maintaining normal fat levels in the body. The liver normally contains some fat, which is around 5 to 10% of its weight, but consumption of too much alcohol can lead to higher fat content in the liver. This results in a condition called fatty liver disease, which is associated with decreased liver function and liver damage. Unfortunately, this condition is becoming more common in non-drinkers, as a result of excess fat in our diets. This occurrence of non-alcoholic fatty liver disease can eventually lead to a more severe condition called non-alcoholic steatohepatitis, or NASH. A recent review paper, published in Exercise and Sport Sciences Reviews, summarized the recent research on the beneficial effects of exercise on NASH and fatty liver disease.
NASH often affects those who are obese, overweight, or diabetic. There are currently no standard treatments for NASH, aside from certain recommended lifestyle changes. Exercise has been hypothesized to help with fatty liver disease, and there are clinical studies that show some benefit. It was recently discovered that the beneficial effects of exercise are due to a process called autophagy. Autophagy is a degradation process used by cells to “clean up” unnecessary or dysfunctional parts. This process degrades excess lipids and proteins and is important for keeping our cells healthy and functional. The mitochondria or “powerhouse” of the cell is responsible for energy production. Liver cells use a lot of energy, and therefore depend greatly on mitochondria. However, having a high-fat diet over a long period of time has been shown to reduce the function of mitochondria, resulting in less energy for the liver. Furthermore, long-term high-fat intake will negatively impact the ability of liver cells to degrade excess fat.
By limiting fat intake through changes in the diet, fat levels in the liver can be directly reduced. It is less clear how exercise can directly reduce liver fat levels, but some scientists hypothesize that exercise causes the liver to produce more energy for our muscles by degrading fat in the liver. Similarly, even though there is evidence from multiple animal studies that exercise can stimulate autophagy, the underlying pathways are unclear. It is believed that during exercise, signals secreted from muscle cells can trigger autophagy to occur in the liver, but further studies are needed to determine the specific pathways.
This review summarizes the evidence for exercise-induced autophagy and how it can improve fatty liver disease. It appears that exercise may improve liver function in patients, but additional research to further our understanding of the process is needed. Although exercise and dietary changes can help with fatty liver disease, there are currently no available treatments. Thus, advances in this field of research may lead to development of treatments against different types of fatty liver disease.
Written By: Branson Chen, BHSc