In the UK most people with a fatty liver are overweight or obese. The condition is linked to problems such as diabetes, high blood pressure (a longstanding complication of diabetes) and high cholesterol. When all these factors are present they are known medically as metabolic syndrome, or syndrome X.
More rarely, people can get a fatty liver because of some drug treatments and intravenous feeding.
Very rapid weight loss can also lead to fat building up in the liver. It is thought this may result from a sudden, massive release of free fatty acids into the bloodstream following the breakdown of fat stored in fat cells. This can sometimes follow surgery to reduce obesity, such as a gastric bypass.
Fatty liver and obesity
Not everyone who is overweight or obese will develop a fatty liver and not everyone who has a fatty liver is overweight. However, the majority of people with non alcoholic fatty liver disease are overweight.
The terms ‘overweight’ and ‘obese’ describe two different categories above what is considered a healthy body size.
As tall people are generally heavier than short people, a person’s weight is not particularly useful in assessing their risk of fatty liver disease or metabolic syndrome. The ratio between height and weight, known as the body mass index (BMI), is a more useful measurement. Calculating body mass index (BMI) is now the accepted method for working out whether you are normal, overweight or obese.
A healthy BMI is regarded as being between 18.5 and 25kg/m². A BMI between 25 and 30kg/m² is defined as overweight. If your BMI is over 30kg/m² then you qualify as obese.
Obesity can also be defined according to the distribution of fat on your body. Fat that gathers on your hips can make you look pear-shaped (known as ‘gynoid’) while having fat around your abdomen will give you an apple-shaped appearance (‘android’). It is known, for example, that obese people with insulin resistance most commonly have abdominal fat.
In men, abdominal obesity is defined in a waist circumference greater than 40 inches or 102 cm. In women, this is a waist circumference greater than 35 inches or 88 cm.
However, the normal range for BMI and waist circumference is not based on how people look.
It is based on their likely risk of developing health problems according to how much they are overweight or obese (BMI-related morbidity).
There are more overweight and obese people in the UK than any other country in Europe but not as many as there are in the US. For the majority, the root causes of becoming overweight or obese are down to:
- eating too much (and too much fatty food in particular)
- drinking too much alcohol
- not doing enough exercise.
In England alone, more than one in five people (20%) are now defined as obese. A similar ratio is now emerging among boys and girls aged between 2 and 15 years.
As more and more people in the UK lead inactive lives and carry extra weight around with them, so the number of cases of fatty liver, in particular NASH, is rising.
Fatty liver and diabetes
Diabetes mellitus, or type 2 diabetes, usually develops in men or women over 40 years of age although it is now being seen in overweight children.
It is a condition that occurs when your body cannot regulate the amount of glucose in your blood. Glucose is a sugar produced when you digest your food. It is also produced and stored by your liver.
Blood glucose levels are regulated by insulin, a hormone produced by your pancreas. Problems start when your body either does not produce enough insulin (as in type I diabetes) or if the muscle, liver and fat cells do not respond normally to insulin. This latter situation is called insulin resistance and leads to a high level of glucose in the blood (hyperglycemia), which is harmful.
Insulin also helps your liver to metabolise (process) fats and to release them into the blood. While fats are a necessary source of energy, too much fat in the blood is bad for you. It is now thought that insulin resistance interferes with this process and causes an accumulation of triglyceride fats in the liver cells.
Having too much triglyceride and another lipid that may be better known, cholesterol, in the bloodstream is known as hyperlipidaemia. Cholesterol is also taken in from our diet and produced by the liver.
High levels of a so-called ‘bad’ cholesterol known as LDL cholesterol (low density lipoprotein cholesterol) can lead to heart disease. Counter to this, there is a ‘good’ cholesterol (HDL, high density lipoprotein cholesterol) that removes the LDL cholesterol and gets rid of it through the liver.
Thus, having a ratio of high LDL to low HDL in the blood is not desirable.
Measuring blood lipids
Cholesterol levels in your blood are most accurately measured by taking a blood sample after you have fasted for nine to twelve hours. This may be done as part of a ‘lipid profile’ which will measure levels of total cholesterol, LDL cholesterol, HDL cholesterol and tryglycerides.
Levels are recorded in millimoles per litre (mmol/L).
The target levels your doctor may recommend for you will be based on the risk to your health from factors such as age, weight, family history, lifestyle or any existing medical condition(s).
Below are guidelines to what your results or ‘numbers’ may mean.
Medications associated with fatty liver
A number of drugs prescribed for other conditions have been linked with fatty liver. In some cases this liver damage is related to high doses of the drug. With other drugs the fatty liver only occurs in a small minority of people. This is known as ‘idiosyncratic drug reaction.’
The drugs most commonly associated with causing fatty liver in this way are:
- prednisolone and hydrocortisone, used to treat inflammation
- premarin and ortho-est (synthetic estrogen), for menopause
- amiodarone, used to treat heart arrhythmia
- tamoxifen, used to treat breast cancer
- diltiazem, used to treat high blood pressure
- methotrexate, used to treat rheumatoid arthritis
Acute fatty liver in pregnancy
Very rarely, some women in the last three months of their pregnancy can develop a fatty liver. Acute fatty liver in pregnancy (AFLP) is more common in first pregnancies and with male babies – especially twins.
AFLP is a very serious condition that can cause rapid liver and kidney failure and can be fatal for both mother and baby if not diagnosed. Hospitalisation and immediate delivery of the baby is usually required.
Provided there has been no permanent damage, the liver returns to normal after the baby has been born.
It is not known what causes this type of fatty liver and, due to the rarity of AFLP, it is unclear whether the problem will happen in any future pregnancies as not enough data is available for study.