What Is Fatty Liver, Why Does It Develop, and What Problems Does It Cause?

Some people may not have heard of fatty liver, or, in more medically accurate terms, fatty liver disease , but it would not be wrong to describe it as perhaps one of the most common diseases in recent years. This term is often used as the equivalent of Nonalcoholic Fatty Liver Diseaseand refers to fat accumulation in the liver "not caused by alcohol." In the United States, approximately 10 to 46 percent of the population is known to have fatty liver disease. Following advanced fat accumulation, the proportion developing inflammation or liver damage is between 3-12 percent.

Compared with a healthy liver, a fatty liver is slightly larger and has lost its characteristic color. Tissue samples show fat deposits specific to nonalcoholic fatty liver disease (image on the left).

How does fatty liver develop?

When the body produces too much fat, or the fat produced cannot be properly broken down and used, the liver is the main tissue in which it accumulates. Fatty liver is present when fat accounts for more than 5-10% of the liver's weight. Fatty liver may develop during pregnancy or result from excessive alcohol use. Excessive alcohol consumption means more than 2 alcoholic drinks daily for women and more than 3 for men.

One alcoholic drink equivalent is: 

• A 5% alcoholic drink, 341 ml; beer, cider, etc. 
• A 12% alcoholic drink, 142 ml; wine, etc. 
• A 40% alcoholic drink, 43 ml; vodka, whisky, rakı, etc. Daily consumption above these amounts is highly likely to result in "alcohol-related fatty liver."

Alcohol-related liver damage can cause cirrhosis and liver cancer (other alcohol-caused cancers include colon, breast and pharyngeal cancer, etc.). Alcohol-related fatty liver is preventable and generally improves when drinking stops.

Nonalcoholic fatty liver disease

Most fatty liver cases are of this type, called "nonalcoholic fatty liver disease." It is considered a separate diagnosis and managed differently by doctors. Although it sometimes causes serious health problems, it often produces no noticeable complaints. Nevertheless, appropriate lifestyle changes (particularly diets low in sugar and trans fats) can restore the fatty liver to its former healthy state.

Fatty liver can make it harder for the liver to function and sometimes trigger liver diseases. Nonalcoholic fatty liver is the most common cause of liver disease in Western countries. Despite its frequency, of every 10 affected patients, one or two are at risk of developing progressive disease (such as liver fibrosis). Over time, 10-25% of those with nonalcoholic fatty liver may develop cirrhosis and advanced liver failure. This is the third cause of liver transplantation in the United States and is expected to become the leading cause in the 2020s.

What are the causes and risk factors of nonalcoholic fatty liver?

Nonalcoholic fatty liver is strongly associated with obesity, insulin resistance (IR) / type 2 diabetes mellitus (T2DM), and metabolic syndrome .

Obesity, particularly increased waist circumference (central obesity), is highly predictive of fatty liver and disease progression. Approximately 70% of people with obesity have fatty liver, compared with 10-15% of lean people. In severe (morbid) obesity, nearly all patients develop fat accumulation in the liver, and more than one third have liver inflammation.

The association between type 2 diabetes (DM) and fatty liver is also very strong. In patients with nonalcoholic fatty liver, type 2 DM is 5-9 times more common. On the other hand, in type-2 diabetes, considering 3 patients, at least 2 have nonalcoholic fatty liver. Type 2 DM is also associated with progression to cirrhosis and liver cancer.

At least one third of patients with nonalcoholic fatty liver have metabolic syndrome, and among 5 patients, 4 have at least one component.

Fatty liver and metabolic syndrome;

• Excess weight and central obesity (a body type with a large waist circumference),
• Increased insulin resistance,
• High cholesterol or high blood fat (triglyceride) levels,
• High blood pressure, 
• together with diabetes or glucose intolerance (prediabetes), form a cluster of cardiovascular risk factors.

Why does nonalcoholic fatty liver develop in people without obesity?

• smoking 
• older age 
• steroids used for cancer treatment and tamoxifen and certain other medications 
• poor eating habits
• rapid weight loss 
• infections affecting the liver, such as hepatitis 
• exposure to substances toxic to the liver
• genetic influences

Fatty liver in children

Fatty liver disease is mostly seen in middle age. However, it can occur in anyone, even children. A review published in 2016 mentioned that of every 10 children, 1-2, and among children with obesity, 50-80%, are expected to have fatty liver.

What are the symptoms of fatty liver?

Nonalcoholic fatty liver disease generally causes no signs or symptoms. However, the following signs and complaints may develop later.

• fatigue
• abdominal swelling and right-sided abdominal pain due to an enlarged liver
• accompanying enlargement of the spleen
• enlarged blood vessels just beneath the skin's surface
• breast enlargement in men 
• red palms (palmar erythema)
• yellowing of the skin and eyes (jaundice)

How is fatty liver diagnosed?

Ultrasonography, computed tomography and MRI (magnetic resonance) can show fat in the liver; a biopsy can confirm fatty liver. Ultrasonography is more reliable in moderate and advanced fatty liver, while its sensitivity is known to be lower when fat accumulation is below 33%. In advanced stages, blood tests can also check how well the liver functions.

How is fatty liver treated?

There is not yet an approved medication for the medical treatment of fatty liver disease. Although studies suggest that medications containing metformin reduce fatty liver, the most valid treatment approach appears to be first losing weight if overweight, reaching a healthy weight and then maintaining an ideal weight.

• Choose a healthy diet. In particular, the Mediterranean diet plays a very important role in both preventing and treating fatty liver (fruits, vegetables, whole grains and healthy fats are among its core features).
• Lose weight healthily. Since obesity is considered the main cause of nonalcoholic fatty liver, even a reduction of only 3-5% of body weight will help treatment.
• Exercise! Exercise can be done on most days of the week. Developing a regular exercise habit is important for treatment and prevention.
• Avoiding alcohol or reducing it as much as possible matters in treatment. In addition to early detection through regular medical checks, early diagnosis and healthy lifestyle choices and practices can reduce and reverse damage.

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