Fatty liver disease: what is it exactly?

Fatty liver disease is something I come across regularly in my work as a nutritionist. It refers to an accumulation of excess fat inside liver cells, and despite how common it has become, it is still often misunderstood and usually associated with alcohol. But is it really the case?

In reality, there are different forms. What was traditionally called fatty liver disease is now referred to as steatotic liver disease (SLD). One form is driven primarily by excessive alcohol intake. Another, now the most common, is not caused by alcohol at all. This means it is possible to drink little or no alcohol and still develop fatty liver disease. There is also a third form, where alcohol and metabolic factors overlap.

In this article, and in my work as a nutritionist, I focus on the non-alcoholic form. The reason is simple: it has become the most common liver condition worldwide, affecting around one in three people in the UK. Liver disease remains a significant contributor to premature death, with rates having increased fourfold since the 1970s. As a result, supporting liver health has become an important part of long-term health.

What causes fatty liver disease?

First of all, it depends on the form.

In alcohol-associated fatty liver disease, fat accumulates in liver cells as a result of excessive alcohol intake. 

In the non-alcoholic form, the drivers are different and more closely linked to metabolic health. Diet can play a role, particularly when it’s high in sugar, refined carbohydrates and highly processed foods. But metabolic factors are just as important: raised LDL cholesterol, high triglycerides, insulin resistance and type 2 diabetes all increase the likelihood of fat building up in the liver. Alcohol is not the primary cause here, but it can add further strain in people who already have metabolic risk factors.

Understanding the stages of progression

Fatty liver disease tends to develop gradually. Not everyone progresses in the same way, and changes usually take place over years rather than months.

Stage 1: mild steatosis

At this earliest stage, small amounts of fat begin to accumulate in liver cells.

• Fat is present, but inflammation and scarring are absent
• Liver blood tests are often normal
• Early metabolic risk factors may already be developing

Stage 2: MASLD (metabolic dysfunction–associated steatotic liver disease)

MASLD is diagnosed when excess liver fat is present alongside metabolic risk factors such as insulin resistance, type 2 diabetes, raised blood pressure or changes in cholesterol and triglycerides.

• Fat accumulation is established, inflammation and scarring are usually minimal or absent
• Most people experience no obvious symptoms
• Metabolic risks factors are present

MASLD now affects around 30% of adults globally and is the most common form of chronic liver disease.

Stage 3: MASH (metabolic dysfunction–associated steatohepatitis)

In some individuals, MASLD progresses to MASH. At this stage, fat accumulation is accompanied by liver inflammation and liver cell injury.

• Inflammation increases the likelihood of progression
• There is a higher risk of developing liver scarring (fibrosis)

From there, a small proportion of people may progress to cirrhosis, and later, liver cancer.

How is fatty liver disease currently managed, and why acting early makes sense?

At the moment, there is no single medication routinely used to treat MASLD or MASH. In some cases, medication may be prescribed to manage related metabolic issues, but diet and lifestyle remain the main tools for improving liver health.

The good news is that, in the earlier stages, liver fat and inflammation can improve with appropriate nutritional and lifestyle changes. This is one of the reasons fatty liver disease is worth paying attention to early on.

The challenge is that the liver doesn’t send clear warning signals. It has no pain receptors, so changes can develop quietly for years. By the time symptoms appear, changes are often harder to reverse. For this reason, being proactive rather than reactive makes a real difference.

Why diet and lifestyle changes are worth considering and why does it matter?

Fatty liver disease is easy to ignore, especially early on as many people feel perfectly well while it’s developing.

So why would you really care?

The liver pays a central role in blood sugar regulation, fat and cholesterol metabolism, hormone processing and detoxification. When excess fat and inflammation are present, these processes become less efficient.

But that is not the only reason: improving liver health is not only about avoiding more serious liver problems later on. In practice, people with MASLD are more likely to experience cardiovascular problems than liver-related ones. Supporting liver health is therefore also part of supporting long-term metabolic and cardiovascular health.

When to pay closer attention?

Fatty liver disease often appears alongside other metabolic changes. If you’ve been dealing with:

 – insulin resistance or type 2 diabetes

 – rising LDL cholesterol or triglycerides

 – blood sugar issues

 – weight gain around the abdomen

 – ongoing low energy

Then it is worth paying attention to liver health as part of the bigger picture.

Let’s have a chat!

I see fatty liver disease regularly in my work, often in people who had no idea it could apply to them. With the right support, things can change!

If you feel like you want to have a chat or would like individual support, I offer one-to-one nutrition consultations on Mondays from 2 to 5 pm.