HIIT, or high-intensity interval training, is one of the fastest ways to burn fat and improve cardiovascular health. Plus, it’s a boredom buster! If you’ve ever worked out on cardio machines where you do the same movements over and over, you’ll quickly discover what a refreshing change HIIT training is. The list of benefits high-intensity training offers is long and now there’s another one. HIIT training protects the health of your liver.
Did you know almost 20% of people have an unhealthy liver and most don’t even know it? These unlucky individuals have a condition called non-alcoholic fatty liver disease, or NAFLD. This disorder is common in people who have metabolic syndrome or who are obese. Fatty liver is a condition characterized by fat build-up around the liver that’s unrelated to drinking alcohol, another common cause of liver disease.
If more than 5 to 10% of your liver is composed of fat, that’s abnormal and you likely have a fatty liver. Surprisingly, many people with non-alcoholic fatty liver have no symptoms or have very vague ones like fatigue. Why is fatty liver so bad? In a small percentage of people, a swollen liver becomes inflamed and goes on to become fibrotic and scarred. In a small minority of people, this condition progresses to cirrhosis and liver failure, requiring a liver transplant. This progression can happen slowly over decades.
Why Liver Health is Important
When you think about how many essential roles your liver plays in health – nutrient processing, processing of toxins, blood clotting, breaking down medications, hormones, and toxins, and supplying glucose to your body when you need it – you understand how important it is to keep it healthy. NAFLD is a possible precursor to more serious liver problems and it’s under-diagnosed. If you have insulin resistance, you’re very much at risk for non-alcoholic fatty liver disease and should discuss the issue with your physician.
Exercise is Good for Your Liver
What does this have to do with HIIT training? A study carried out by researchers from Newcastle University in the United Kingdom showed HIIT training is effective for reducing liver fat accumulation and may help reverse fatty liver. Fortunately, non-alcoholic fatty liver disease is very responsive to lifestyle changes and can be reversed or significantly improved in the majority of cases. High-intensity interval training could be another way to do that and keep your liver healthy if you don’t already have NAFLD.
HIIT for Fatty Liver: What Research Shows
In the Newcastle University study, obese participants took part in 12 weeks of HIIT training three times a week for 30 minutes. Another group served as a control group. Researchers used MRI imaging to quantify liver fat and also followed their body composition and glucose levels. By the end of the study, the participants who did HIIT enjoyed a significant reduction in liver fat and total body fat. Their liver enzymes were also improved, suggesting their liver was experiencing less metabolic stress.
Another study showed ALL types of exercise, including high and low intensity aerobic and resistance training, has some benefit for fatty liver, but improvements were greatest with short, high-intensity exercise like HIIT training and with longer periods of aerobic exercise. However, HIIT has the advantage of being less time intensive. What’s significant is improvements in fatty liver in these studies were independent of weight loss, another lifestyle factor that helps reverse fatty liver.
Other Lifestyle Factors that Lower the Risk for Fatty Liver
As you can see, HIIT training is good for your liver and for improving the insulin resistance that fuels fatty liver. As you might expect, diet is a factor too. According to Dr. Mark Hyman, director of the functional medicine department at the Cleveland Clinic, high-fructose corn syrup, found in many processed foods, is the strongest promoter of fatty liver disease.
Although all sugary foods are unhealthy, fructose is processed differently by your body than glucose. Unlike glucose, fructose can’t enter most cells easily. It’s primarily taken up by liver cells and they promptly convert it to triglycerides. Some proponents of high-fructose corn syrup argue that studies showing high-fructose corn syrup cause fatty liver disease is misleading because the subjects consumed very high quantities of high-fructose corn syrup. More research is needed, but it’s prudent to avoid high-fructose corn syrup and processed foods if you’re trying to optimize your health.
Another way to prevent fatty liver and help reverse it if you have it is to get down to a healthy weight and maintain it. In people who are overweight or obese and have family liver, losing as little as 10% of body weight can improve fatty liver and the insulin resistance that goes along with it. If you’re at a normal body weight, don’t let your weight creep up over the years as it has a tendency to do, especially if you don’t exercise consistently. Resistance training, too, is vital for achieving a healthier body composition and avoiding sarcopenia.
Simply sitting less can help you avoid the scourge of non-alcohol fatty liver. A Korean study found a correlation between extended periods of sitting and higher rates of NAFLD, independent of structured physical activity. Don’t assume because you do a structured workout that it’s okay to sit the rest of the day. It’s not. Take walking and stretching breaks every 20 minutes.
Help Your Liver Function Better
Remember, your liver is the master detoxifier. That’s why you want to keep it healthy. One way to support your liver’s ability to detox is to eat more cruciferous vegetables, like broccoli, cabbage, kale, and Brussels sprouts. The more whole foods and the fewer processed ones you eat the better. If you do discover you have fatty liver, ask your doctor about taking a vitamin E supplement. Research shows vitamin E, an antioxidant vitamin, may reduce liver inflammation in people with NAFLD.
The Bottom Line
High-intensity interval training is not only good for your heart – it helps you avoid a problem that affects one in five people – non-alcoholic fatty liver disease. Combine it with good nutrition and you’ll lower your risk for a number of other diseases as well.
References:
Clin Sci (Lond). 2015 Aug 11. pii: CS20150308. [Epub ahead of print]
Medical Press. “New study indicates that exercise improves non-alcoholic fatty liver disease”
Today’s Dietitian. Vol. 11 No. 12 P. 28
Aliment Pharmacol Ther. 2012;35(10):1135-1144.
American Liver Foundation. “Fatty Liver Disease”
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