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What is Non-Alcoholic Fatty Liver Disease (NAFLD)?

Non-alcoholic fatty liver disease (NAFLD) is a condition in which there is a buildup of excess fat in liver tissue. It is often seen in people who are overweight or obese and is called a steatotic liver disease. NAFLD is one of the most common liver diseases in the United States and affects up to a quarter of the population. It is different from alcohol-associated liver diseases that develop due to heavy alcohol use. 

Nonalcoholic Fatty Liver Disease (NAFLD): NAFL vs NASH

Nonalcoholic Fatty Liver (NAFL)

NAFL is the common type of NAFLD in which there is a fat buildup in liver cells, but no inflammation, liver damage, or other complications. However, people with NAFL can develop pain due in the upper right abdomen to an enlarged liver. About 24% of adults in the United States have NAFL.

Nonalcoholic Steatohepatitis (NASH)

NASH is the more serious form of NAFLD in which there is fat buildup in liver cells accompanied by inflammation and liver damage. This can progress to fibrosis (scar tissue) in the liver and, ultimately, permanent scarring called cirrhosis. Cirrhosis can lead to liver cancer. About 1.5-6.5% of adults in the United States have NASH.

Symptoms, Causes, Risk Factors, and Related Conditions

Symptoms: How Does A Fatty Liver Make You Feel?

Many people with NAFLD feel normal and don’t have any symptoms. When present, symptoms are usually nonspecific and can include fatigue, malaise (feeling generally unwell), and pain in the right upper abdomen. 

People with the more severe form of NAFLD, called nonalcoholic steatohepatitis (NASH), can develop the following symptoms due to cirrhosis (severe scarring):

• Itchy skin

• Swelling in the legs

• Shortness of breath

• Spider veins 

• Reddening of the palms

• Jaundice (yellowing of the skin and eyes)

Complications

Left untreated, the liver scarring (cirrhosis) can lead to complications such as:

• Ascites (fluid buildup in the abdomen)

• Esophageal varices (swollen veins in the esophagus, which can rupture and bleed)

• Hepatic encephalopathy (confusion, slurred speech, and drowsiness due to brain dysfunction caused by liver dysfunction)

• Hypersplenism (overactive spleen and a low platelet count)

• End-stage liver failure

• Liver cancer

Causes of NAFLD

Researchers in digestive and kidney diseases have not been able to identify the exact cause of fat build-up in the liver, but they believe it is a combination of genetic and environmental factors. They also don’t know why some people develop NAFL (the less severe form) and others NASH (the more severe form with liver scarring). 

Risk Factors for NAFL and NASH

• Genetics (family history of fatty liver disease)

• Obesity

• High blood sugar

• Metabolic syndrome (a set of conditions including high blood pressure, high triglyceride levels, high cholesterol, insulin resistance, and a large waist size)

Some people develop NAFLD without having any risk factors. Keep in mind that while there are many overlapping risk factors between NAFLD and NASH, people older than 50 are more likely to develop NASH. 

Related Conditions

NAFLD is more likely in people with certain other health conditions, including:

• Obesity, especially belly fat centered around the waist area

• Insulin resistance (reduced responsiveness of cells in the body to the hormone insulin)

• Type 2 diabetes (hyperglycemia or high blood sugar)

• Hypercholesterolemia (high cholesterol)

• Hypertriglyceridemia (high levels of triglycerides, which are a type of blood fats)

• Growth hormone deficiency

• Metabolic syndrome (central obesity, high cholesterol, high blood pressure, and insulin resistance - a set of conditions linked to an increased risk of heart disease and type 2 diabetes)

• Obstructive sleep apnea

• Polycystic ovary syndrome

• Hypothyroidism (underactive thyroid)

• Hypopituitarism (underactive pituitary gland)

Learn more: Is My Liver Healthy? Quiz Yourself

How is NAFLD Diagnosed?

NAFLD is often discovered after a discussion of symptoms with your doctor and on routine blood tests or tests for other conditions that reveal signs of liver problems, such as elevated liver enzymes. 

If your doctor suspects NAFLD, they may order other tests, including: 

• Blood tests — complete blood count, liver function tests, blood test to detect chronic viral hepatitis such as hepatitis C, iron studies, testing for celiac disease, blood sugar levels, and lipid profile.

• Imaging tests — abdominal ultrasound, MRI, transient elastography, or FibroScan, a new type of ultrasound to measure stiffness in liver tissue, and magnetic resonance elastography, a combination of MRI and elastography.

• Liver biopsy — a procedure in which a small sample of liver tissue is obtained by passing a needle through the abdominal wall. This tissue sample is examined in the laboratory for signs of inflammation and scarring. A liver biopsy can provide a definitive diagnosis of NASH by showing the extent of liver damage. 

How Do You Treat Non-Alcoholic Fatty Liver Disease?

Lifestyle and Dietary Changes

Weight loss is the first line of therapy for NAFLD. This can be achieved by eating a healthy diet and getting daily exercise. Weight loss to the tune of 10% of initial body weight can improve many of the health problems related to NAFLD. However, losing even 3-5% of the initial weight has health benefits. 

Medical Treatments

The U.S. Food and Drug Administration (FDA) has approved a prescription medication called resmetirom (Rezdiffra) to treat adults with NASH. This drug is used, along with diet and exercise, in adults with nonalcoholic steatohepatitis (NASH) who have moderate to severe liver scarring (fibrosis) but not cirrhosis. Rezdiffra can reduce hepatic steatosis (the amount of fat that builds up in the liver) and prevent liver cell damage. 

Surgical Treatments

A liver specialist may recommend bariatric surgery (weight loss surgery) for those who aren’t able to lose weight through diet and exercise alone. People with cirrhosis due to NASH and end-stage liver failure may need to undergo a liver transplant. 

Living with Nonalcoholic Fatty Liver Disease

Prognosis and Life Expectancy

What Is The Life Expectancy Of A Person With A Fatty Liver?

The life expectancy of a person with fatty liver depends on the severity of the disease.

• Mild disease: Simple fatty liver with minimal scarring does not affect a person’s quality of life or life expectancy. Studies have found that, on average, the life expectancy of people with NAFLD is about 2-3 years less compared to people who don’t have fatty liver disease. 

• Moderate disease: People who develop scarring and liver injury have a life expectancy of about 10 to 15 years with early diagnosis and treatment. 

• Advanced disease: People who develop complications of fatty liver disease, such as ascites, hepatic encephalopathy, or bleeding esophageal varices, have a life expectancy of 3-5 years without a liver transplant.

How Long Does It Take For Nonalcoholic Fatty Liver To Turn Into Cirrhosis?

It can take decades, as much as 30 years, for fatty liver to turn into cirrhosis, which is the main complication of NAFLD. This means a person who develops fatty liver in their 30s may not be diagnosed with cirrhosis until they are in their 60s. However, with the increasing prevalence of obesity in young people, cirrhosis from fatty liver is being seen even in adolescents. This is because the longer the body has excess abdominal weight, the more time there is for extra fat to accumulate in the liver.

Preventing Nonalcoholic Fatty Liver Disease

The following healthy lifestyle changes can lower your risk of developing NAFLD:

1. Eat a healthy diet. This includes eating fruits, vegetables, whole grains, lean proteins, and healthy fats, and limiting the intake of fried and fatty foods and sugary foods and beverages. 

2. Exercise regularly. Aim to be active on most days of the week. Talk to your healthcare provider before starting any new exercise program, especially if you have been inactive for a long time.

3. Maintain a healthy weight. If you are overweight or obese, make changes to your diet and exercise to help you in losing weight. If you are a healthy weight, maintain it by eating a healthy diet and exercising daily.

Stop drinking alcohol. Alcohol use is a known risk factor for liver damage. Drink alcohol in moderation if you must. Avoid alcohol if you have signs of liver injury.