With the same weight loss, keto cut liver fat the most

Researchers at Washington University School of Medicine in St. Louis set three quite different diets the task of producing the same weight loss, then looked at what had changed in the body's metabolism. In their study, published on 27 August 2026 in the journal Cell Metabolism, keto came out ahead on liver fat and blood sugar, with LDL cholesterol no different from the other two diets.

How the study worked

Fifty-five people with obesity, prediabetes and fatty liver were randomly assigned to one of the three diets. Forty-two made it to the end, fourteen in each group, with an average age of 43. The research team supplied all the food and participants saw a dietitian every week.

The percentages show each nutrient's share of the calories. Calories were adjusted so that everyone lost about 10% of their body weight, which took 4.6 months in the keto group, 5.4 on the Mediterranean diet and 5.1 on the plant-forward one. Whatever differences turned up, then, cannot be put down to how much weight each group lost.

What they found

Weight came down by almost the same amount in everyone, 11.4 to 11.9 kg on average, and muscle sensitivity to insulin rose by about 50% across all three groups. In the liver, however, insulin sensitivity improved two to three times as much in the keto group.

On keto, liver fat fell by roughly two thirds, against a little under half in the other two groups. HbA1c, the blood test that reflects blood sugar over recent months, also dropped furthest on keto.

Of the three diets, the keto one had by far the most fat. Even so, LDL cholesterol, apolipoprotein B and 24-hour triglycerides did not differ between the groups.

What it does not show

The sample was small; the researchers themselves note that some differences between the groups may simply not have shown up. Because the food arrived ready-made, participants ate more than 95% of their meals, and the study cannot tell us how someone cooking for themselves would get on.

It also remains open whether a gentler cut in carbohydrate, without ketosis, would give the same results (we explain how keto differs from low carb in the guide Keto, high-protein or low carb). Nor do we know whether the liver benefit needs keto while you are losing weight, or would also come with keto once the weight is off. The authors leave both questions open in the study's limitations.