The liver acts as a cleansing organ of the body by removing toxic/harmful substances and performs hundreds of other vital functions. It plays an important role in the metabolism of drugs and nutrients to produce energy.

Fatty Liver

Fat in the liver (fatty liver) typically develops when a person consumes more fat and sugars than his or her body can handle. This is more common in people who are overweight or obese but can also occur in adults with healthy body weights. If fat builds up to more than 5% of the liver, then the liver is considered to be a fatty liver. Although having this condition may not cause any immediate harm or damage to liver cells, there is a concern that extra fat in the liver might make the liver vulnerable to further injuries such as inflammation and scarring. Fatty liver disease is sometimes called a silent liver disease. This is because it can happen without causing any symptoms.

How fat accumulates in the liver

Fat and sugars from a person’s diet are usually broken down by the liver and other tissues. If the amount of fat or simple sugar intake exceeds what is required by the body, fat is stored in the fatty tissue. Other reasons for the accumulation of fat in the liver could be the transfer of fat from other parts of the body or the inability of the liver to change it into a form that can be eliminated.

Symptoms

In general, people with fatty liver disease have no symptoms. However, some people report discomfort in the abdomen at the level of the liver, fatigue, a general feeling of being unwell, and vague discomfort.

Diagnosis

Fatty liver disease is usually suspected in people who are overweight and obese (particularly those with large waist circumferences), who have evidence of dyslipidemia (high cholesterol and lipids in the blood), insulin resistance and/or abnormal liver tests. An ultrasound or Fibroscan® of the liver can show the presence of a fatty liver. In some cases, doctor may advise a liver biopsy, a procedure where the physician inserts a needle into the liver and extracts sample tissue, which is then examined under a microscope.

Also Read: Liver, Our Bodyguard: What Are the Most Important Functions of the Liver In Our Body?

Types of Fatty Liver

1. Non-alcoholic Fatty Liver Disease (NAFLD)

Non-alcoholic fatty liver disease (NAFLD) is a liver disease affecting people who drink little to no alcohol. As the name implies, the main characteristic of NAFLD is too much fat stored in liver cells. NAFLD is a distinct hepatic condition and one of the most common causes of chronic liver disease globally. In a recent meta-analysis, the estimated prevalence of NAFLD worldwide is approximately 25.2%. NAFLD is one of the most common causes of liver disease in the United States. Experts estimate about 24% of U.S. adults have NAFLD. NAFLD is already the fastest growing cause of hepatocellular carcinoma (HCC) in the USA, France and the UK. Globally, the prevalence of NAFLD-related HCC is likely to increase concomitantly with the growing obesity epidemic.

The highest prevalence was observed in the Middle East (31.8%) and South America (30.4%) while the greatest increase was detected in Europe (23.7%), North America (24.1%) and Asia (27.4%) and the lowest in North Africa (13.8%).  In India, NAFLD leading to hepatitis and cirrhosis is an emerging problem. Around 10 lakh patients of liver cirrhosis are newly diagnosed every year in India. Liver disease is the tenth most common cause of death in India as per the World Health Organization. Over the past three decades, NAFLD has gone from an obscure liver disorder to the most prominent chronic liver disease worldwide.  NAFLD is closely associated with a group of metabolic diseases which include: obesity, type 2 diabetes mellitus, hypertension, and hypercholesteremia.

There are two different types of nonalcoholic fatty liver disease:

1. Simple fatty liver: This means there is fat deposition in the liver, but without causing inflammation in the liver or damage to liver cells. It usually doesn’t get worse or cause problems with the liver. Most people with non-alcoholic fatty liver disease (NAFLD) have simple fatty liver. Mild fatty liver and slight liver enlargement are very common which are diet-induced like processed food, junk food, fried and oily food, etc, slow metabolism, and less physical activity to burn them. The fatty liver normally does not cause altered liver enzymes which are mainly due to infections, alcohol, chemotoxins, etc.
2. Non-alcoholic steatohepatitis (NASH): This is much more serious than a simple fatty liver. About 20% of people with NAFLD have NASH. NASH means inflammation in the liver. The inflammation and liver cell damage that happen with NASH can cause serious problems such as fibrosis and cirrhosis (I out of 5 adults), which are types of liver scarring, and liver cancer.  For about 1 out of 10 people with NASH, it may lead to liver failure and the need for a liver transplant. The prevalence of NASH in the general population is estimated to be between 1.5% and 6.45%. A recent modeling study estimated that the prevalence of NASH in the United States will increase 63% by 2030, leading to an increased incidence of NASH-related cirrhosis by 168%, cancer (HCC) by 137%, liver-related deaths by 178%, and causing approximately 800 000 excess liver deaths.

2. Alcohol-Related Fatty Liver Disease (ALD)

 Alcohol-related fatty liver disease (ALD) usually comes first. It can then get worse and become alcoholic hepatitis. Over time, it may turn into alcoholic cirrhosis. ALD may result in fatal liver failure. Alcohol is a toxic and psychoactive substance. According to World Health Organization (WHO), alcohol consumption contributes to 3 million deaths each year globally as well as to the disabilities and poor health of millions of people. Overall, the harmful use of alcohol is responsible for 5.1% of the global burden of disease. ALD is a major cause of alcohol-related morbidity and mortality.

Its presentation ranges from fatty liver to alcoholic hepatitis (AH; swelling in the liver, belly pain, jaundice), cirrhosis (scar tissue), and hepatocellular carcinoma (HCC; liver cancer). Cirrhosis occurs in approximately 20% to 25% of patients who drink heavily over many years. Chronic alcohol use of approximately 20 to 50 g/day for women or 60 to 80 g/day for men increases the risk for alcoholic cirrhosis. In summary, NAFLD prevalence is increasing worldwide and the disease is being diagnosed in all parts of the world. This dramatic and significant increase in NAFLD prevalence is alarming and suggests that NAFLD has emerged as a new public health concern worldwide. More efficient prevention strategies are urgently needed.

References

1. Y Zobair M, M Giulio, PC Helena, P Salvatore (2019).  Epidemiology of Nonalcoholic Fatty Liver Disease and Nonalcoholic Steatohepatitis: Implications for Liver Transplantation. Transplantation. Volume 103: 22-27.
2. D Q Huang, H B El-Serag, R Loomba (2021).  Global epidemiology of NAFLD-related HCC: trends, predictions, risk factors and prevention. Nature Reviews Gastroenterology & Hepatology. 18 :223–238.