脂肪肝疾患：知っておくべきこと

Fatty liver disease is on the rise—and with it can come an increase in liver cancer cases. With no routine screening and no early symptoms, this condition often flies under the radar. The good news is there are steps you can take to prevent or reverse fatty liver disease and reduce your cancer risk. Read on to learn about fatty liver disease and how it’s linked to cancer.

What is fatty liver disease?

Fatty liver disease is a disorder of excessive fat buildup (steatosis) in the liver. Over time, it can interfere with the functioning of your liver and cause liver damage.

There are two main types of fatty liver disease: non-alcoholic fatty liver disease (NAFLD) and alcohol-related fatty liver disease (AFLD).*

NAFLD is further classified into two categories:

• Simple fatty liver: There’s excessive fat storage but little to no inflammation or liver damage.
• Non-alcoholic steatohepatitis (NASH): The liver shows both inflammatory changes and cellular damage.

NAFLD accounts for 25% of total cases and is more common among adults in the U.S. than AFLD (which only accounts for 5% of total cases) but rates of both are increasing—particularly for NAFLD, which is currently estimated to affect between 35.3%-47.8% of U.S. adults.¹

Who’s at risk for fatty liver disease?

For NAFLD, the strongest risk factors are metabolic disorders, including:

• Obesity
• Diabetes
• High blood pressure
• High levels of cholesterol or triglycerides in the blood.

Other factors, such as a person’s genes or gut microbiome, may also increase the risk for NAFLD and are currently being researched.

Typically, NAFLD affects middle-aged or older adults, but due to rising rates of adolescent obesity, it’s being seen more often in children and teens.

The rates of NAFLD are highest among Hispanics/Latino people (63.7%), followed by non-Hispanic white people (56.8%), and non-Hispanic Black people (46.2%).² NAFLD rates are continuing to rise across each of these racial/ethnic groups.

For AFLD, the most common risk factor is excessive alcohol intake, including heavy or binge drinking, usually over a long period of time.

Other factors that can increase fatty liver disease risk include viral hepatitis infection and some medications, like steroids.

How do you know if you have fatty liver disease?

For people with NAFLD, those with simple fatty liver may never experience any symptoms, while those with NASH may see symptoms as the degree of liver damage increases. As it progresses, symptoms may include fatigue and right sided abdominal pain or fullness. Worsening symptoms, including nausea, vomiting and jaundice, may occur from progressive damage, which can eventually cause liver scarring (cirrhosis), abdominal fluid buildup (ascites) and liver failure.

For those with AFLD in the early stages, there may be no signs or symptoms. As it progresses, you may see symptoms like the above. Because there are often no symptoms, fatty liver disease may be found when you have blood or imaging tests done for other reasons. Liver function tests (liver enzymes) may be elevated or an imaging scan may show abnormalities.

In these cases, your health care provider would first rule out other explanations for the abnormal results. Then they would perform a physical exam and ask about your alcohol use to determine if it may be a contributing factor. Your provider may order imaging tests, such as specialized ultrasound or MRI scan, to look for fat deposits in the liver and evaluate for scarring. Though uncommon, your provider might do a liver biopsy to definitively diagnose fatty liver disease and help distinguish its cause.

How do you treat fatty liver disease?

The first step in treatment of fatty liver disease in those who are overweight is to lose weight gradually (1-2 pounds/week), which helps reduce fat and inflammation. More rapid weight loss can worsen the condition. For those who are thin, treatment of metabolic issues (such as elevated cholesterol or diabetes) is key. Those who drink alcohol will also be advised to stop.

There are some medications that can help with NASH.

Depending on the degree of fatty liver disease, many of the changes may be reversible through these steps and your cancer risk can return to normal. It’s then critical to maintain healthy lifestyle behaviors to prevent fatty liver disease from returning.

How do you prevent fatty liver disease?

Prevention is key when it comes to fatty liver disease. Lifestyle choices such as maintaining a healthy weight; eating a well-balanced diet of lean proteins, fruits, vegetables, beans and whole grains while limiting alcohol, foods or drinks high in fat or sugar and highly processed foods; and regular physical activity can help reduce the risk for fatty liver disease and improve overall health. 

Why is fatty liver disease important when it comes to cancer and what should I do?

If fatty liver disease progresses, the resulting liver scarring, or cirrhosis, can increase the risk of developing liver cancer. While progressive AFLD has long been associated with increased liver cancer risk, NAFLD is also linked to increased liver cancer risk. In fact, some research has shown NASH to be the fastest growing cause of liver cancer globally.³ Those who have fatty liver disease along with obesity, diabetes, metabolic syndrome or hepatitis may also have an increased risk for liver cancer.

Make sure to take the preventive steps outlined above to prevent fatty liver disease, reduce your liver cancer risk and improve your overall health. If you have any of the above conditions associated with fatty liver disease, talk with your health care provider about your risk. If you do receive a fatty liver diagnosis, don’t despair; work with your health care provider to reverse the damage and stop cancer before it starts.

*In 2023, liver experts renamed non-alcoholic fatty liver disease (NAFLD) to metabolic dysfunction-associated steatotic liver disease (MASLD), and non-alcoholic steatohepatitis (NASH) to metabolic dysfunction-associated steatohepatitis (MASH). Readers will likely see both terms being used in various publications while the transition of names is ongoing.

¹Teng et al. Global incidence and prevalence of nonalcoholic fatty liver disease. Clinical and Molecular Hepatology, 29(Suppl), S32-S42.

²Shaheen et al. Trends in the racial and ethnic disparity of metabolic associated fatty liver disease (MAFLD): Data from NHANES 1988 to 2018. Journal of Endocrine Society. 2023. 7(Suppl 1).

³Huang et al. Changing global epidemiology of liver cancer from 2010 to 2019: NASH is the fastest growing cause of liver cancer. Cell Metabolism, 34(7), 969-977.e2