Do diets high in fast-digesting carbs and excess calories cause insulin resistance and fatty liver disease?

We looked at 73.0 studies or data points that support this link, and 0 that refute it ¹. These findings suggest that when people regularly consume more calories than their bodies need—especially from sugary or starchy foods—their cells may become less responsive to insulin over time. This condition, often called insulin resistance, can lead to changes in how the body processes fat. In some cases, this appears to result in fat building up in the liver, even in people who don’t drink alcohol. This buildup is a hallmark of non-alcoholic fatty liver disease ¹.

It’s important to note that our current analysis is based on limited assertions—only one has been fully evaluated so far—even though it draws from a large number of supporting studies. We don’t yet have a complete picture, and more evidence may change how we understand these relationships over time.

We’re not saying this happens the same way in everyone, nor are we claiming this is the only factor involved. Other elements like genetics, activity levels, and overall diet quality likely play roles too. But based on what we’ve reviewed so far, there’s a consistent signal that excessive calorie intake, particularly from rapidly digested carbs, is linked with these metabolic changes.

Practical takeaway: If you're aiming to support long-term metabolic health, paying attention to both the amount and type of calories you eat—especially limiting sugary and starchy foods—may help reduce the risk of insulin resistance and fatty liver.