Let’s get physical: Listen to your liver talk!

June 25, 2015 By: Rui Castro

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Let’s get physical: Listen to your liver talk! 

Does exercise benefit NAFLD patients?

Summer is just around the corner and I’ve been hitting the gym more often to get ready for the beach (and by more often I mean I actually started going to the gym)! But there are many more important reasons why you should work out and your liver’s health is a major one, particularly concerning non-alcoholic fatty liver disease (NAFLD).

NAFLD consists of a spectrum of histopathological changes that range in severity from simple steatosis to non-alcoholic steatohepatitis (NASH). Although simple steatosis is characterized by a relatively favourable clinical outcome, NASH can progress to cirrhosis and hepatocellular carcinoma, leading to liver-related morbidity and mortality. Largely considered a manifestation of obesity and the metabolic syndrome, NAFLD is becoming the most common cause of chronic liver disease worldwide. Indeed, NAFLD is found in almost 70% of the adult obese population and in more than 90% of morbidly obese individuals.1 NAFLD is also highly prevalent in children and its incidence appears to be increasing in Europe, with 2–12.5% of children and early adolescents presenting with NAFLD, a number that rises to 36–44% in obese children.2 Of note, the risk factors for paediatric NAFLD mirror those for adult NAFLD and further correlate with an increasingly sedentary lifestyle, coupled with unbalanced dietary habits, where changes in macronutrients, increased calorie intake and decreased physical activity negatively influence NAFLD pathogenesis.

There is no current pharmacological treatment for NAFLD, although several clinical trials are ongoing, with promising results reported so far. As a consequence, lifestyle interventions remain the cornerstone of NAFLD treatment; in parallel with healthier and smarter eating choices, the benefit of physical activity for NAFLD patients has recently been expounded. Originally thought to be effective only when combined with the introduction of a healthy diet in obese patients, it is now apparent that different exercise regimens can benefit NAFLD, even without dietary restriction and/or in the absence of significant weight loss. For instance, aerobic exercise alone has been shown to be able to decrease visceral adipose tissue volume and liver fat content in sedentary obese individuals by 12% and 21%, respectively.3 Similarly, Oh and co-workers showed that increased physical exercise with or without dieting significantly reduced hepatic inflammation and associated oxidative stress in obese men.4

More recently, Oh and colleagues have suggested that at least 250 minutes of moderate to vigorous intensity physical exercise per week was required to reduce liver fat in obese men as part of lifestyle management.5 In other words, this is more or less equivalent to 50 minutes of moderate (dancing, gardening, housework/domestic chores, walking domestic animals) to vigorous (walking, running, fast cycling/swimming, aerobics, competitive sports/games) intensity physical activity, 5 times per week. Not bad at all! But it gets even better. In April 2015, Keating et al. showed that inactive and overweight/obese adults placed under different aerobic exercise regimens reduce their liver fat and visceral adipose tissue, irrespective of exercise volume or intensity and in the absence of clinically significant weight loss!6 In my opinion, these findings suggest that regular exercise may also greatly benefit non-obese NAFLD patients, despite there being no expectation that these patients will lose a significant amount of weight (they are lean!).

Although it might be surprising for some to learn that NAFLD is not solely a disease of the obese population, the prevalence of NAFLD in lean individuals is increasing. This increase in prevalence is particularly noticeable in the Asia-Pacific region, due to diverse environmental and genetic factors.7 As such, if you think you have ‘good genes’ because you look lean and healthy despite not working out much and/or eating junk food all the time, you might want to think twice, listen to your liver talk and get physical! If nothing else, individuals who exercise regularly might be, perhaps unknowingly, actively lowering their risk of developing fatty liver or even cardiometabolic disease, as the latter correlates with excess liver fat, even in the absence of NASH. However, the key word here is ‘regularly’; if you are a seasonal gym member like me, I would encourage you (and myself) to find other parallel and fun exercise activities and to stick to them. This might be difficult for some, but the sustainability of any intervention is the key to success. This is why—despite believing that specialized and personalized exercise prescription, in parallel with dietary advice, should continue to represent the main line of treatment for NAFLD patients—I think that the use of pharmacological agents on their own or as adjunctive therapies to lifestyle modification will remain desirable.

When exercising, the old saying, “Feel good on the inside and look good on the outside,” usually crosses my mind. Now, I can also almost picture my liver shouting “I feel good, na na, na na, na na, na…”

 

References: 

  1. Angulo P. Nonalcoholic fatty liver disease. N Engl J Med 2002; 346: 1221–12231.
  2. Durmaz O. Metabolic liver disease in the adolescent. Presentation in the Non-alcoholic fatty liver disease (NAFLD): any news? session at UEG Week 2014.
  3. Johnson NA, et al. Aerobic exercise training reduces hepatic and visceral lipids in obese individuals without weight loss. Hepatology 2009; 50: 1105–1112.
  4. Oh S, et al. Exercise reduces inflammation and oxidative stress in obesity-related liver diseases. Med Sci Sports Exerc 2013; 45: 2214–2222.
  5. Oh S, et al. Moderate to vigorous physical activity volume is an important factor for managing nonalcoholic fatty liver disease: a retrospective study. Hepatology 2015; 61: 1205–1215.
  6. Keating SE, et al. Effect of aerobic exercise training dose on liver fat and visceral adiposity. J Hepatol Epub ahead of print 1 April 2015. DOI: 10.1016/j.jhep.2015.02.022.
  7. Bugianesi E. Non-obese patients with NAFLD. Presentation in the Non-alcoholic fatty liver disease (NAFLD): any news? session at UEG Week 2014.

 

Further UEG Resources:

Bellentani, S. How frequent is NAFLD in Europe and in the world? Presentation in the Update on non-alcoholic fatty liver disease session at UEG Week 2013

Dufour J-F. Impact of lifestyle and diet on disease progression. Presentation in the Non-alcoholic fatty liver  disease (NAFLD): any news? session at UEG Week 2014.

Ratziu, V.  Medical treatment. Presentation in the Non-alcoholic fatty liver disease (NAFLD): any news? session at UEG Week 2014.

Ratziu, V. Treatment modalities for non-alcoholic steatohepatitis. Presentation in the Non-alcoholic fatty liver disease (NAFLD) and alcoholic liver disease in 2014 session at UEG Week 2014. 

About the author

Dr Rui Castro is currently a Principal Investigator at the Research Institute for Medicines (iMed.ULisboa), Portugal. He completed his PhD at the University of Lisbon and the Department of Medicine (GI Division), University of Minnesota Medical School, USA, in 2006. Since then, Dr Castro has been combining his background on the modulation of liver cell function with his most recent discoveries in the miRNA field, to answer key questions on liver physiology and pathophysiology, while supervising both undergraduate and postgraduate students under the GI umbrella. In 2015, he was selected as a UEG Rising Star. Follow Rui on Twitter @RuiCastroHD.

 

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