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Exercise as it relates to Disease/Fatty Liver and Aerobic Exercise

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Fatty Liver

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What is it?

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Fatty liver is a condition that is diagnosed when over 10% of the livers weight is from fatty acids and triglycerides.[1][2] The two types of fatty liver disease are alcoholic fatty liver disease (AFLD) and non-alcoholic fatty liver disease (NAFLD).

Diagnosing

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Fatty liver disease may go by unnoticed for long period of time as there may be no symptoms during the early to moderate stages of the condition.[3] 3 methods of diagnosing:[4]

  • Liver Biopsy - Gold standard, but unable to distinguish between AFLD and NAFLD, which needs to be determined by the assessor.
  • Imaging Machines - Reliable for diagnosing moderate and severe cases.
  • Serology - Not for diagnosing the condition itself, but for ruling out other possible conditions and diseases.

Causes and Risk Factors

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AFLD is caused by the acute consumption of an excess of alcohol, and may develop into alcoholic hepatitis if lots of alcohol is consumed over a prolonged period.[5] NAFLD has no direct pathogenic causes; however, there are risk factors and probable causes.[3] It has been regarded as a manifestation of metabolic syndrome (insulin-resistance syndrome), so all of the associated risk factors may also influence NAFLD.[6] The main factors include:[2][7]

  • Obesity, especially central/abdominal obesity
  • Hypertension
  • Abnormal cholesterol levels (high triglycerides, or low high density lipoproteins)

Insulin resistance is one of the largest contributing factors due to its cascading effect on the liver:

  1. Blood glucose levels cannot be down regulated, and muscle glucose levels cannot be replenished
  2. Causes the mobilisation of free fatty acids and triglycerides to the target muscles and liver cells [4][6][8]
  3. The liver cannot synthesise glycogen or suppress gluconeogenesis, resulting in excess glucose production[6]
  4. Excess glucose is unable to be aerobically metabolised from the increased insulin, and the exocytosis via very low density lipoproteins is suppressed, so some of it will be converted into more fats (de novo lipogenesis)[4]
  5. As the fat builds up in the liver, without a way of using it, the body stores the excess energy in the hepatocytes, thus creating a fatty liver[2]

Other risk factors that may lead or warn about a potential fatty liver include:

  • Diabetes[2]
  • Fat cell inflammatory proteins (adipose cytokines/adipokines)[3]
  • Rapid weight loss[9]
  • Some medications[9]

Complications and Progressions

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NAFLD is the broad term used for the condition of excess fat in the liver; however, there are different levels of severity:

  • Fatty liver disease (steatosis) - term used when the liver contains excess fat, and there is no inflammation or scarring[9]
  • Non-alcoholic steatohepatitis (NASH) - the next progression on from steatosis, where the liver becomes inflamed and/or damaged[3]
  • Cirrhosis - a slowly progressing disease where permanent scar tissue slowly replaces the healthy liver tissue, which then impairs its functioning by blocking the blood flow through the liver. It hinders nutrients, toxins, hormaones, drugs and all other substances created in the liver[10]

From NASH, the liver may take years or decades to progress any further, into a serious condition of cirrhosis, where there is permanent damage and scarring to the liver.[3]

Effects of Aerobic Exercise

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The main goal of aerobic exercise is to try to improve insulin resistance, and other factors that contribute towards metabolic syndrome.

  • Insulin Resistance - exercise doesn't directly have an effect on insulin resistance, but it does influence abdominal fat, which is directly related to the resistance.[11]
  • Obesity - aerobic exercise for prolonged periods of time has been shown to utilise fat as the main fuel source. Where, the lower the intensity, the greater the contribution of fats for energy.[12]
  • Central Obesity - studies have shown that exercising aerobically will reduce the amount of abdominal fat, if completed regularly over time.[13][14] Other studies have also found that central fat was decreased more than other areas of the body.[15]
  • Cholesterol - large decrease in the amount of triglycerides available in the plasma due to them being used as the main fuel source.[14] High density lipoprotein levels also increase with aerobic exercise.[16]
  • Blood pressure/hypertension - aerobic exercise helps to lower blood pressure in both hyperintensive and normotensive individuals.[17]

Recommendations and Interventions

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If someone is suffering from AFLD, then they should stop consuming alcohol immediately and undergo abstinence to let their body fix itself. professional help may be needed to help the individual not to drink, and for any problems that my arise.[5] Regular aerobic exercise is a great way to reduce and combat the precursor signs of NAFLD. The aerobic exercise should be:

  • a low to moderate intensity so that they are predominately utilising their fat stores for fuel,[12]
  • continuous exercise bouts greater than 10 minutes minimum, to ensure benefits such as high density lipoproteins,[16]
  • and as often during the week as possible, 30 minutes on most if not all days.[18]

Eating healthy and correctly also plays a major role in helping to treat fatty liver disease, and should be done with exercise.[1][2][3][4][6]

References

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  1. ↑ a b Saenger M, 2012, Fatty liver disease, WebMD, viewed 18 October 2013, <http://www.webmd.com/hepatitis/fatty-liver-disease>
  2. ↑ a b c d e Better Health Channel, 2012, Liver – fatty liver disease, Victoria, viewed 18 October 2013, <http://www.betterhealth.vic.gov.au/bhcv2/bhcarticles.nsf/pages/Liver_disease_fatty_liver_disease>
  3. ↑ a b c d e f National Digestive Diseases Information Clearinghouse, 2012, Nonalcoholic steatohepatitis, New York, viewed 20 October 2013, <http://digestive.niddk.nih.gov/ddiseases/pubs/nash/
  4. ↑ a b c d Adams LA, Angulo P, Lindor KD, 2005, Nonalcoholic fatty liver disease, CMAJ, vol. 172, no. 7, pp. 899-905
  5. ↑ a b Fairbanks KD, 2012, Alcoholic liver disease, Cleveland Clinic, Cleveland, viewed 18 October 2013, <http://www.clevelandclinicmeded.com/medicalpubs/diseasemanagement/hepatology/alcoholic-liver-disease/>
  6. ↑ a b c d Farrell GC, Larter CZ, 2006, Nonalcoholic fatty liver disease: from steatosis to cirrhosis, Hepatology, vol. 43, no. 2, pp. 99-112
  7. ↑ Better Health Channel, 2011, Metabolic syndrome, Victoria, viewed 20 October 2013, <http://www.betterhealth.vic.gov.au/bhcv2/bhcarticles.nsf/pages/Metabolic_syndrome>
  8. ↑ Utzschneider KM, Kahn SE, 2006, Review: the role of insulin resistance in nonalcoholic fatty liver disease, The Journal of Clinical Endocrinology & Metabolism, vol. 91, no. 12, pp. 4753-4761
  9. ↑ a b c Rossiter a, 2013, Fatty liver disease, Bupa, viewed 20 October 2013, <http://www.bupa.co.uk/individuals/health-information/directory/f/fatty-liver-disease>
  10. ↑ Johnson K, 2012, Cirrhosis of the liver, WebMD, viewed 23 October 2013, <http://www.webmd.com/digestive-disorders/cirrhosis-liver?page=3>
  11. ↑ Cuff DJ, Meneilly GS, Martin A, Ignaszewski A, Tildesley HD, Frohlich JJ, 2003, Effective exercise modality to reduce insulin resistance in women with type 2 diabetes, Diabetes Care, vol. 26, no. 11, pp. 2977-2982
  12. ↑ a b Romijn JA, Coyle EF, Sidossis LS, Gastaldelli G, Horowitz JF, Endert E, Wolfe RR, 1993, Regulation of endogenous fat and carbohydrate metabolism in relation to exercise intensity and duration, American Journal of Physiology - Endocrinology and Metabolism, vol. 265, pp. 380-391
  13. ↑ Okura T, Nakata Y, Lee DJ, Ohkawara K, Tanaka K, 2005, Effects of aerobic exercise and obesity phenotype on abdominal fat reduction in response to weight loss, International Journal of Obesity, vol. 29, pp. 1259-1266
  14. ↑ a b Short KR, Vittone JL, Bigelow ML, Proctor DN, Rizza RA, Coenen-Schimke JM, Nair KS, 2003, Impact of aerobic exercise training on age-related changes in insulin sensitivity and muscle oxidative capacity, Diabetes, vol. 52, no. 8, pp. 1888-1896
  15. ↑ Despres JP, Pouliot MC, Moorjani S, Nadeau A, Tremblay A, Lupian PJ, Theriault G, Bouchard C, 1991, Loss of abdominal fat and metabolic response to exercise training in obese women, American Journal of Physiology - Endocrinology and Metabolism, vol. 261, pp. 159-167
  16. ↑ a b Kodama S, Tanaka S, Saito K, Shu M, Sone Y, Onitake F, Suzuki E, Shimano H, Yamamoto S, Kondo K, Ohashi Y, Yamada N, Sone H, 2007, Effect of aerobic exercise training on serum levels of high-density lipoprotein cholesterol, Archives of Internal Medicine, vol. 167, no. 10, pp. 999-1008
  17. ↑ Whelton SP, Chin A, Xin X, He J, 2002, Effect of aerobic exercise on blood pressure: a meta-analyses of randomized-controlled trials, Annals of Internal Medicine, vol. 136, no. 7, pp. 493-503
  18. ↑ The Department of Health, 2013, Physical activity guidelines, viewed 23 October 2013, <http://www.health.gov.au/internet/main/publishing.nsf/Content/health-pubhlth-strateg-phys-act-guidelines>
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