What it is
Fatty liver disease is a build-up of excess fat inside liver cells. When it is not caused by alcohol it is called MASLD, short for metabolic dysfunction-associated steatotic liver disease. This replaced the older term NAFLD in 2023. It sits on a spectrum: fat alone, then fat plus inflammation (MASH), then scarring (fibrosis), and finally cirrhosis.
Symptoms to look out for
Fatty liver usually causes no symptoms and is often found by chance. Advanced liver disease can cause:
- Yellowing of the skin or eyes (jaundice)
- Swelling of the abdomen or legs
- Easy bruising or bleeding
It is often first suspected from mildly abnormal liver blood tests, though these can be normal even when fat is present.
What causes it
There are two main drivers: the body's safe fat stores are full, and a diet high in sugar and refined carbohydrate, which the liver turns into fat. Fructose, in sweet foods, sugary drinks and fruit juice, is a particular driver. Inactivity and stress contribute. It goes with excess belly fat, prediabetes or type 2 diabetes, raised triglycerides (blood fat) and high blood pressure.
The liver's expression of insulin resistance
Fat in the liver is fat that should not be there. This is called ectopic fat, and it is central to insulin resistance. It is both a result of poor metabolic health and a cause of further problems, which is why it often occurs alongside prediabetes, type 2 diabetes and a large waist. Liver fat reduces quickly with lifestyle improvement, often faster than fat stored elsewhere.
What you can do
- Food. Reduce sugar, sugary drinks, refined carbohydrate and ultra-processed food. Build meals with plenty of protein and non-starchy vegetables, with starchy carbohydrate reduced, or adjusted to the amount that suits you. See the Metabolic Health 28 Day Plan at healthshelf.org/28-day-plan.
- Movement. Both aerobic (e.g. walking, running, cycling) and resistance (muscle building) exercise reduce liver fat, even without much weight change.
- Alcohol. Stay within the UK limit of 14 units a week at most, or avoid it, as alcohol adds directly to liver fat and damage.
Medicines
There is no long-established drug for simple fatty liver, but treatments for the more advanced form (MASH) are emerging. GLP-1 medicines such as semaglutide can reduce liver fat, and are advised where someone also has type 2 diabetes or obesity. Specialists may consider vitamin E or pioglitazone for advanced scarring. If you take a statin, keep taking it.
When to get help
- See your clinician if liver blood tests are abnormal, or if you have risk factors such as type 2 diabetes or a large waist.
- Seek prompt help for jaundice, abdominal swelling or other signs of advanced liver disease.
- Discuss your alcohol intake honestly, as it strongly affects the liver.