What is non-alcoholic fatty liver disease (NAFLD)?

Non-alcoholic fatty liver disease (NAFLD) includes a range of liver conditions caused by a build-up over time of fat in the liver. Whilst a healthy liver should contain either no fat or a small amount of fat, estimates show that in the UK 1 in 3 people have early signs of having NAFLD. Dr Daniel Forton, a leading hepatologist, explains why awareness of NAFLD is more important than ever before.

What is non-alcoholic fatty liver disease?

Non-alcoholic fatty liver disease is now considered to be the most important chronic liver disease in the western world, with prevalence rates as high as 30%. Fatty liver is commonly seen as an incidental finding on ultrasound examinations and is suggested by mildly abnormal liver function tests in individuals with obesity, diabetes, hypertension and dyslipidaemia (high cholesterol or high triglycerides).

NAFLD covers a range of liver conditions that affect people who drink little to no alcohol. The management of NAFLD involves firstly the exclusion of other liver disorders, an assessment of the likelihood of liver fibrosis and treatment with lifestyle, nutritional and pharmacological means.

What causes non-alcoholic fatty liver disease?

NAFLD is associated with having too much fat stored in the liver cells and it is most frequently associated with obesity, insulin resistance, hypertension and dyslipidaemia. Fat deposition in the liver can also be due to certain drugs, small bowel bypass surgery and hepatitis C. NAFLD can represent a broad spectrum of liver conditions, ranging from simple steatosis (fat retention) without inflammation, to severe inflammatory activity with significant fibrosis or even cirrhosis. The combination of steatosis and inflammation are the hallmarks of non-alcoholic steatohepatitis (NASH), a more serious form of NAFLD.

How common is non-alcoholic fatty liver disease?

Estimates of the presence of NAFLD depend on the method used to screen for it. The Dallas Heart Study examined 2349 subjects using a sensitive technique (magnetic resonance spectroscopy) and found significant liver steatosis in 34% of North Americans (1). In Italy, the Dionysos study used ultrasound in over 3,000 subjects and estimated a population prevalence of 20-25%. In at-risk groups, the prevalence is much higher with an estimated prevalence of 50% in type-2 diabetics, and 60-90% in obese individuals.

What treatment options are there for non-alcoholic fatty liver disease?

NAFLD is a component of the wider metabolic syndrome and associated conditions (dyslipidaemia, diabetes, hypertension and obesity) and should be treated as part of a broad health-improvement strategy. This includes a combination of lifestyle changes, nutritional and pharmacological therapies.

Lifestyle measures:

• Dietary changes and exercise may lead to weight loss with parallel improvements in liver inflammation.
• Although weight loss is often a primary goal in overweight and obese individuals, aerobic exercise may also increase insulin sensitivity and improve liver steatosis, even in the absence of weight loss.

Nutritional therapies:

• Diets designed to modulate risk factors for ischaemic heart disease in diabetic and obese individuals are appropriate for NAFLD.
• A diet containing omega-3 fatty acids, olive oil, fruit and vegetables, low GI and high fibre foods is recommended.
• Food that is high in saturated fat, simple carbohydrates and sweetened is not recommended.
• Fructose found in processed foods and carbonated drinks should also be avoided.

Pharmacological therapies:

• Currently there are no specific licensed medications for treating NAFLD, but there are a number of clinical trials that show promise, with some medications helping to manage the problems associated with this condition, including reversal of liver scarring. Opportunities exist for patients to participate in clinical trials
• Research also suggests that a pharmacological dose of vitamin E - an antioxidant could help to reduce the damage caused by liver inflammation. There are advantages and disadvantages of this treatment, which should be discussed with an expert.

So, should we be concerned about fatty liver disease?

Fatty liver and its complications are closely linked with obesity, which is projected to increase in the UK over the next 20 years. Liver disease is the only major cause of death that continues to increase year on year and is currently the fifth biggest killer in the UK. This highlights the need for increased awareness of NAFLD.

If you would like to find out more about non-alcoholic fatty liver disease, make an appointment with a liver specialist.

(1) Szczepaniak LS et al. (2005). Magnetic resonance spectroscopy to measure hepatic triglyceride content: prevalence of hepatic steatosis in the general population. Am J Physiol Endocrinol Metab 288, E462-68.