Fatty Liver Disease

Fatty liver disease occurs when excess fat builds up in liver cells. A small amount of fat in the liver is normal, but too much can lead to inflammation and, over years, scarring that affects how well the liver functions.

Main Types

• Metabolic dysfunction-associated steatotic liver disease (MASLD), previously called non-alcoholic fatty liver disease (NAFLD) — the most common type, linked to obesity, type 2 diabetes, and insulin resistance rather than alcohol use
• Alcohol-associated liver disease — caused by heavy alcohol consumption
• MetALD — a category between the two, for people who have MASLD's metabolic risk factors along with higher alcohol intake than the MASLD definition allows

Risk Factors

Excess body weight (particularly around the abdomen), type 2 diabetes or prediabetes, insulin resistance, high cholesterol or triglycerides, and metabolic syndrome are all strongly linked to MASLD. Our insulin resistance guide covers a closely related underlying process.

Why Early Detection Matters

Fatty liver disease in its early stage (simple steatosis) often causes no symptoms and doesn't necessarily progress further. But in some people, it advances to inflammation — now also called metabolic dysfunction-associated steatohepatitis (MASH), previously known as NASH — and eventually scarring (fibrosis or cirrhosis), which can seriously affect liver function. Because early stages are silent, it's often found incidentally during imaging or blood tests done for other reasons.

Our symptoms of fatty liver disease guide covers what to watch for as it progresses.