What is fatty liver disease?
Non alcoholic fatty liver disease (NAFLD) is quickly becoming the most common form of chronic liver disease across the world (1). It is already the most prevalent form of chronic liver disease in children and it is becoming more common (2).
NAFLD is characterised by hepatic fat accumulation contributing to >5% of the livers weight (3). This means an abnormal amount of fat is stored within the liver cells. Other causes of fat infiltration must firstly be ruled out before a diagnosis of NAFLD is made.
This type of liver disease has a strong association with abdominal obesity, insulin resistance, type 2 diabetes and cardiovascular disease. In some severe cases it can progress to cirrhosis or hepatocellular cancer. For these reasons, a healthy diet and lifestyle are extremely important for prevention and treatment.
Prevalence
The prevalence of NAFLD amongst children is 3-10%, and these figures increase to 40-70% in children who are obese (1)!
In adults, NAFLD affects 80-90% of those who are obese and up to 90% of adults with hyperlipidaemia (2).
The sharp increase in the prevalence of NAFLD is thought to be a result of the rising obesity rates and subsequent metabolic risk factors that accompany excess weight. It has been labelled as the ‘hepatic manifestation of metabolic syndrome’ (4).
What causes it?
Both genetic and lifestyle factors seem to determine the development and progression of NAFLD. However, its pathophysiology is still somewhat unclear (2). Despite this, obesity or being overweight, along with a lack of physical activity, appear to be major players in its pathogeniesis, along with male gender. This can be largely attributed to the insulin resistance that commonly goes hand in hand with excess weight (5).
It has been hypothesised that by preventing risk factors such as weight gain and the development of metabolic abnormalities, there may be a marked reduction in the predicted prevalence rate of NAFLD (6). However, there are still uncertainties surrounding all of the potential causes of NAFLD.
The science
Some researchers suggest a “two hit hypothesis” when it comes to the development and progression of NAFLD (2, 3). NAFLD encompasses a spectrum of chronic liver disorders including:
- Simple steatosis – fat accumulation within the liver
- Non Alcoholic SteatoHepatitis (NASH)
- Advanced fibrosis
- Cirrhosis
- Hepatocellular carcinoma (liver cancer)
The first type of NAFLD involves only the accumulation of fat within the liver with no other damage present (7). The second type involves fat within the liver along with liver damage such as inflammation and scaring -this is classified as Non Alcoholic SteatoHepatitis (NASH) (7).
It is quite rare that the disease progresses as far as the ‘second hit’ (development of NASH). In most cases, NAFLD is well managed and reversed or does not cause any damage to the liver cells. The two processes are explained in further detail below.
First hit
The accumulation of fat within the hepatocites (liver cells) occurs when normal lipid movement through the liver cells is disrupted. The accumulating fat may be caused by:
- Dietary intake
- Peripheral insulin resistance – there is an increase in the transport of fatty acids from body fat stores to the liver
- Decreased exportation of free fatty acids
- Fatty acid synthesis through a process called ‘de novo lipogenesis’ (the creation of fatty acids)
The triglycerides derived from body fat stores seem to have the biggest impact on the excess fat stores within the liver (5). It can also occur during rapid weight loss or re-feeding syndrome whereby the delivery of triglycerides to the liver is also increased (5).
Second hit
The second hit involves the disease progression from simple steatosis (fat accumulation) involved with NAFLD to NASH, which results in injury, inflammation and fibrosis. This is attributed to oxidative stress and in severe cases, can lead to cirrhosis.
The diagram below shows the possible progression of the disease.
The diagram below shows changes from the ‘first hit’ to the ‘second hit’ whereby damage to the liver cells result.
Figure sourced from: ‘Pediatric non alcoholic fatty liver disease: old and new concepts on development, progression, metabolic insight and potential treatment targets’ (2)
Prevention
Prevention and treatment is directed toward decreasing the known risk factors. Given that there is a very strong link between insulin resistance/excessive weight and NAFLD, diet and lifestyle intervention is one of the top strategies in reducing risk.
Dietary management
Making healthy changes to your diet is very important in the management/prevention of fatty liver disease. The emphasis is placed on reducing the amount of fat consumption and avoiding foods that will encourage weight gain, e.g. energy dense foods that are high in sugar and/or fat.
The basic idea is to:
- Reduce fat/ cholesterol intake from the diet
- Eat a healthy, balanced diet
- Avoid foods or portion sizes that will encourage weight gain – even too much of a healthy food can cause weight to creep on
Weight management
Reaching or maintaining a healthy weight is very important for minimising the risk factors associated with fatty liver disease. In saying that, rapid weight loss is not recommended for any one with fatty liver disease. A gradual approach is the key. As mentioned previously, this is because triglyceride delivery to the liver can be accelerated if weight is lost very quickly.
Weight loss and dieting should not be a goal for children. Rather, their diets should be altered to be as healthy as possible and meet all of their requirements whilst also avoiding excessive weight gain. In doing this, overweight children should be able to fall within a healthy weight range as they grow.
Contact us for results focused nutritional advice
This article was written by our dietitian Belinda Elwin who is a Dietitians Association of Australia member and Accredited Practising Dietitian and Nutritionist.
If you have any questions about nutrition related issues or specifics on how to manage fatty liver disease, you can make an appointment with Belinda today. We‘ll provide you with a simple and effective routine targeted to your concerns. Contact us today.
References
1. Epidemiology of non-alcoholic fatty liver disease
2. What is non-alcoholic fatty liver disease?
3. Pediatric non alcoholic fatty liver disease
4. A manifestation of the metabolic syndrome
5. Pathogenesis of nonalcoholic fatty liver disease
6. What causes non-alcoholic fatty liver disease and its progression?
7. Types of fatty liver disease
