Fatty liver disease (MASLD): causes, tests and lifestyle care

The liver helps digest food, stores energy and removes toxins ^[4]. When too much fat collects in it, the liver can become inflamed and, over time, scarred. This article explains fatty liver disease, drawing on the NHS, the US National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) and MedlinePlus.

1. Introduction

Fatty liver disease was long called non-alcoholic fatty liver disease (NAFLD). It is now often called metabolic dysfunction-associated steatotic liver disease (MASLD). Steatotic means fatty, and the NHS and MedlinePlus use both names ^{[1, 4]}. NIDDK explains that it is a condition in which excess fat builds up in the liver and that it is not caused by heavy alcohol use ^[2].

It is one of the most common causes of liver disease. In the United States, about 24 in 100 adults are estimated to have it, and the number is higher among people who are overweight or have type 2 diabetes ^[2]. A form linked to heavy drinking is called alcohol-associated liver disease and is a separate problem ^[4].

2. Stages of the condition

The NHS describes four stages ^[1]:

1. Fatty liver (steatosis): fat builds up without liver damage. Most people stay at this stage.
2. MASH (formerly NASH): metabolic dysfunction-associated steatohepatitis, in which fat causes inflammation, meaning swelling and irritation of the liver ^{[1, 4]}.
3. Fibrosis: inflammation has caused scarring, though the liver usually still works well.
4. Cirrhosis: severe scarring that affects how the liver works. It can lead to complications such as internal bleeding, liver failure and liver cancer.

NIDDK adds that MASH can lead to cirrhosis, and that people with MASH have a higher chance of dying from liver-related causes ^[2].

3. Causes and risk factors

The exact cause is not fully known ^[4]. The NHS lists these things that make fatty liver more likely ^[1]:

• Being overweight, especially with fat around the waist
• An unhealthy diet or little physical activity
• Type 2 diabetes or polycystic ovary syndrome
• High blood pressure or high cholesterol
• Being over 50

NIDDK also names insulin resistance, abnormal blood fats such as high triglycerides, and metabolic syndrome, which is a cluster of problems including a large waist, high blood pressure and raised blood sugar ^[3]. Genes may play a part, and research on diet and gut bacteria is still under way ^[3].

Other things can also cause fat in the liver, including rapid weight loss, some medicines such as corticosteroids, exposure to certain toxins and rare inherited diseases ^{[3, 4]}. Do not stop any medicine without medical advice ^[4].

4. Signs and symptoms

Fatty liver is often called a silent disease, because it usually causes few or no symptoms. Many people find out during tests for another reason ^{[1, 3]}. Some feel very tired, generally unwell, or have discomfort in the upper right part of the tummy ^[1]. Cirrhosis caused by MASH can also happen without symptoms ^[3].

5. Diagnosis and tests

Doctors often suspect fatty liver after abnormal liver blood test results ^[4]. The NHS says a doctor will ask about symptoms, measure height, weight and waist, and ask about alcohol use to rule out alcohol-related liver disease. Further blood tests and sometimes an ultrasound scan may be used to confirm fat build-up, rule out other causes and check for related conditions ^[1].

MedlinePlus adds that imaging can look for liver fat and scarring, and that a biopsy, in which a tiny sample of liver is examined, is used in some cases ^[4].

6. Treatment and prevention

Weight loss is usually the first step when a person is overweight ^[4]. The NHS advises these lifestyle changes, which can help stop the condition getting worse ^[1]. MedlinePlus adds that weight loss can reduce liver fat, inflammation and scarring ^[4]:

• Eat a healthy, balanced diet
• Be active regularly, aiming for at least 150 minutes a week
• Lose weight if you are overweight
• Keep alcohol within recommended limits
• Do not smoke

MedlinePlus suggests a diet that limits salt and sugar and emphasises fruit, vegetables and whole grains. It also advises talking to a doctor about vaccines for hepatitis A and B, and checking with a doctor before taking supplements or herbal remedies, because some can harm the liver ^[4].

If there is no liver damage, regular check-ups are usually enough. If there is fibrosis or cirrhosis, a liver specialist is usually involved, and treatment is decided by the specialist ^[1]. For people with obesity, a specialist may discuss other weight-loss options ^[1].

Linked health risks

NIDDK notes that heart disease is the most common cause of death in people with fatty liver, so heart health, blood pressure, cholesterol and diabetes care matter too ^{[1, 2]}.

7. Special groups

NIDDK reports that close to 10 in 100 US children aged 2 to 19 have fatty liver, so it is not only an adult problem ^[2]. Risk rises with age and with obesity ^{[2, 4]}. One-third to two-thirds of people with type 2 diabetes have it ^[2], and the NHS advises seeing a doctor if you think you are at higher risk ^[1].

8. When to see a doctor

The NHS advises seeing a doctor, as non-urgent advice, if you think you may have fatty liver or may be at higher risk of it ^[1]. Ask for a check if you have diabetes, a large waist, high blood pressure or high cholesterol.

Jaundice, a yellowing of the skin and eyes, is one of the signs doctors look for when checking the liver ^[4], so seek prompt medical care if you notice it. In an emergency, call your local emergency number (112 in India, 911 in the United States).

9. Conclusion

Fatty liver disease is common, often silent and closely linked to weight, diabetes and blood fats. Most people stay at the early stage, but some develop scarring and cirrhosis. Lifestyle changes such as a balanced diet, regular activity, weight loss when needed, limiting alcohol and not smoking are the main steps, and your own doctor decides on any further care.