What is the relationship between fatty liver and type 2 diabetes?

A fatty liver (also known as NAFLD) roughly doubles the risk of developing type 2 diabetes. A meta-analysis of 19 observational studies involving nearly 300,000 participants calculated a risk ratio of 2.22. The more scar tissue (fibrosis) there is in the liver, the higher the risk: advanced fibrosis was associated with an almost fivefold increased risk, although that figure is based on only one study.

The relationship also runs in the other direction. People with type 2 diabetes are themselves twice as likely to have a fatty liver, and if they already do, the situation progresses more rapidly toward liver inflammation and scarring. This makes it a self-reinforcing cycle: each condition accelerates the other.

The central link between the two is that the body responds less effectively to insulin. As a result, fat cells send more fatty acids to the liver, which stores them as fat droplets. At the same time, the liver produces too much glucose. In addition, a fatty liver behaves like a kind of hormonal gland: it secretes substances that also make muscles, fat tissue and the pancreas less sensitive to insulin, further paving the way toward diabetes.

There is also an indication of a causal relationship: when a fatty liver demonstrably improves or resolves, the risk of diabetes falls alongside it. The evidence for this is still limited, but it suggests that treating the liver may also serve as diabetes prevention.

People who have both conditions simultaneously face an additional risk of cardiovascular disease, chronic kidney disease and liver cancer that is greater than with either condition alone. Early intervention in fatty liver disease, for example through weight loss and dietary change, is therefore worthwhile for several reasons.