Effect of Exercise on Non-alcoholic Fatty Liver Disease

Oh My! Fat Accumulation Has Happened in My Internal Organs as Well!

Liver, an important organ in the human body, is not much talked about despite its versatility in fighting against infections, aiding in digestion, storing energy and cleaning the blood. This organ residing in each of us contains a designated amount of fat which is normal but the problem arises when more than 5-10% of the liver’s weight is fat resulting in what is termed as a fatty liver. Non-alcoholic fatty liver disease (NAFLD) is the build-up of excess fat in the liver cells that’s not a result of alcohol commonly seen in overweight or obese people. NAFLD can be split into four stages that includes simple fatty liver (steatosis), non-alcoholic steatohepatitis (NASH), fibrosis and cirrhosis (here, the individual is at risk for hepatocellular carcinoma (HCC)). Many people get into the first stage even before realising what’s happening but it can take years together to reach the 3rd or 4th stage before which significant lifestyle changes can prevent this condition from worsening. Otherwise, such high fat accumulation in the liver paves way for other serious health conditions such as diabetes (this once again increases the risk of heart disease), high BP and kidney disease.
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Prevalent rates of the disease are different in different parts of the world with maximum prevalence of 20-30% recorded in Western countries. Earlier days saw the need for humans to hunt or gather food for fulfilling nutrient requirements and this included energy expenditure to replenish the lost energy with food. But now, despite the prevalence of malnutrition and poverty among a class of people there are a majority of individuals who are provided with a surplus of daily calories thereby increasing the rates of obesity and overweight worldwide. This kind of an obesity epidemic has made it possible for diseases such as NAFLD to become diagnosis of chronic liver disease. Though it can affect any individual of any age it is generally the middle-age people who are affected. Though there are different treatment plans proposed for NAFLD weight loss and lifestyle management exist as the most reliable forms of treatment plans till date. We have research supporting the fact that lifestyle interventions reduce markers of liver lipid and metabolic control along with reducing intrahepatic lipid (IHL) and studies even show that increased exercise practices are linked to lower levels of IHL but it is also essential to remember that weight loss is difficult to achieve and even more difficult to maintain. Even The American Gastroenterological Association, the American Association for the Study of Liver Diseases, and American College of Gastroenterology all of them recommend physical activity as one of the best treatment methods for NAFLD. Given below is a detailed study of hbow exercise affects NAFLD.

Aerobic Exercise As a Tool Against NAFLD
A non-randomized clinical trial segregated 90 NAFLD patients into two groups-case and control groups. Height, weight and BMI calculations were made on each participant. Liver enzymes (AST, ALT, ALP), fasting blood sugar (FBS) and lipid profile (TG, total cholesterol and HDL cholesterol) were measured. In the case group, when TG levels were above 400 mg/dl enzymatic method was used for calculating LDL cholesterol and in the control group, medical therapy with 1000 mg vitamin C and 400 units vitamin E were prescribed. Besides medical therapy (just like the control group) 30 minutes of aerobic exercise with maximal heart rate thrice a week for around 3 months was performed in the case group.

Of the 90 participants 57 of them were men and 33 were women. In the case group, 29 were men and 16 were women while in the control group 28 were men and 17 were women and all of them were between 17 and 56 years of age. Once both groups were done with their stipulated duration of aerobic exercise performance serum levels of enzymes and liver echogenicity in individuals with NAFLD was decreased. It was observed that in the case group, 35 patients were in stage 1, 4 and 6 patients were in stage 2 without sonographic fatty liver. In the control group, 33 patients were in stage 1, 9 patients were in stage 2 and the fatty liver of 3 patients was resolved by sonography. Weight, BMI FBS, TG, HDL, AST, ALT and VFM values varied significantly before and after the trial in the case group. In the control group there was significant difference found in weight, BMI, SBP, DBP, TG and LBM values before and after trial.

Effect of Resistance Training on NAFLD
21 NAFLD patients leading a sedentary lifestyle were involved in the study and each of them were randomly assigned to either the exercise (11 participants) or standard care (10 participants) group respectively. Physical examination, full medical history and fat measures (both subcutaneous and visceral) were done on each of the individuals. The exercise group performed resistance exercises on non-consecutive days for a period of 8 weeks for around 45-60 minutes daily with 10 minutes of warm-up session before the exercise. The programme involved eight exercises and the participants were encouraged to increase resistance used every week when possible.
While 2 participants were removed in between the research quoting various reasons the other 19 participants completed the study. Results showed that BMI remained unchanged in both the groups during the study with insignificant changes seen in weight, waist or hip circumference, waist to hip ratio, body composition and visceral or subcutaneous fat in either group.

There was a 13% reduction in IHL values witnessed in the exercise group on performance of resistance training with no changes seen in the control group. Three participants in the exercise group witnessed great improvements moving over from having significant NAFLD to staying within normal limits whereas none of the control subjects moved into the normal liver fat range. The exercise group also showed improved glucose control and significant improvement in insulin sensitivity. Fasting glucose levels also reduced in the exercise group after intervention compared to the control group. The study is a clear example that resistance exercises reduced IHL, increased insulin sensitivity and improved metabolic flexibility in NAFLD patients independent of weight loss.
 
Evidences in Favour Of & Against Exercises
End-stage liver disease (ESLD) and HCC are the final outcomes of fatty liver disease and we don’t have studies until now showing the effects of exercise on them. But logically, when individuals recover from NASH the risk of going into any of the other stages is minimal. A randomized control study by Eckard et al. focusing on lifestyle interventions that included daily physical activity showed significant reduction of NASH score. Another RCT on 31 NASH patients showed that 48 weeks of intense intervention pave way for a 2.4-point reduction of score.

A 2012 meta-analysis done by Keating et al. on 439 subjects showed only a small reduction in liver fat content. A systematic review by Golabi et al. on 8 randomized trials on 433 individuals showed a 30.2% reduction in hepatic fat that was a result of regular exercising and a 49.8% reduction in liver fat that’s a result of a combination of both exercise and dietary intervention.

There are a couple of studies that focused on the modality, intensity and duration of exercise that had a definite impact on NASH patients. An analysis of 813 NAFLD patients who were asked to self-report on their physical activity status came to the conclusion only those patients who performed vigorous physical activity were at a decreased risk of entering the NASH stage and those patients who doubled the exercise intensity decreased their risk of advanced fibrosis even further. Another study in Japan focusing on five cycles of HIIT training followed by 3-min recovery periods showed an optimal reduction in liver fat. Another study segregated 48 patients randomly into four different groups-low-intensity/high-volume, high-intensity/low-volume, low-intensity/low-volume and no exercise. While each group did experience a significant reduction in liver fat there was not much difference witnessed between the regimens. This shows that aerobic exercise done even at low-intensity reduces fat content of the liver. Another study by Bacchi et al. compared the effects of aerobic versus resistance training on 31 NASH patients over a 4-month period. While liver fat content did reduce there was no difference in results seen between the two exercise forms. A randomized trial on 196 subjects showed that aerobic exercise resulted in a greater reduction in hepatic fat content than resistance training program. But all these studies had one ideology in common-hepatic fat content decreased even when there as no change in weight loss observed in different studies. This clearly shows that physical activity and exercise have a direct impact on the liver.

References
The Effect of Physical Exercise on Fatty Liver Disease: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5954622/
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The Effect of an Aerobic Exercise on Serum Level of Liver Enzymes & Liver Echogenicity in Patients with Non-alcoholic Fatty Liver Disease: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4017540/

Resistance Exercises Reduces Liver Fat & its Mediators in non-alcoholic Fatty Liver Disease Independent of Weight Loss: https://gut.bmj.com/content/60/9/1278