What is the relationship between fatty liver and type 2 diabetes?
Fatty liver and type 2 diabetes mutually reinforce each other, with abdominal fat and insulin resistance at their shared core. For anyone wanting to address both, the most impactful step is to reduce waist circumference through diet and exercise.
Fatty liver and type 2 diabetes reinforce each other in both directions. People with fatty liver have roughly twice the risk of developing diabetes later in life, independent of excess weight or other known risk factors. And conversely, the majority of people with type 2 diabetes develop fatty liver at some point. It is therefore a two-way interaction, not a one-way street.
The common denominator is insulin resistance: the body responds less effectively to the hormone insulin. This simultaneously disrupts fat metabolism in the liver and blood sugar regulation. In addition, fat that accumulates in the liver causes inflammation, which further disturbs both processes. The more advanced the fatty liver is toward scarring, the greater the risk of diabetes as well.
Abdominal fat turns out to be the most important shared driver. A large European study found that waist circumference is a stronger predictor of both fatty liver and diabetes than overall body weight (BMI) or genetic predisposition. In that study, the effect of abdominal fat on diabetes risk was nearly twice as large as its effect on fatty liver. This has a practical implication: reducing waist circumference addresses both problems at the same time.
The good news is that the relationship works in both directions. When a fatty liver improves or resolves, the risk of diabetes also decreases. This suggests that treating fatty liver can have a protective effect. Unfortunately, there are still no approved medications specifically targeting fatty liver. Treatment currently focuses on the shared risk factors: reducing insulin resistance, exercising, and eating more healthily.
Finally, a worrying trend: people with advanced fatty liver most often die not from liver disease, but from cardiovascular disease and diabetes complications. In Europe, the combined disease burden is increasing, including among younger people. This underlines that it is not enough to treat only the liver or only the blood sugar: the approach must encompass both.
Based on multiple observational studies, meta-analyses, and a European Mendelian randomisation study (a method that can support causal relationships more robustly than conventional observational studies). The bidirectional relationship and the role of insulin resistance are well established. The mechanisms at the cellular level are clearer from animal and laboratory research; the treatable causes (abdominal fat) have been demonstrated in humans.