A ketogenic diet helped about half of participants with prediabetes clear their diagnosis within four to five months, according to a randomized clinical trial published August 27, 2026, in Cell Metabolism by researchers at Washington University School of Medicine in St. Louis.
The very low-carb, high-fat pattern also produced sharper drops in liver fat than a Mediterranean or plant-forward diet, even though all three groups lost roughly the same amount of weight.
The trial enrolled 42 adults who had obesity, prediabetes, and excess liver fat. In the keto group, 50% no longer met the criteria for prediabetes at the end of the study, compared with 29% on the Mediterranean diet and 7% on the plant-forward diet.
Liver fat fell by 67% on the ketogenic plan and by 45% on each of the other two diets, the research team reported. Every group lost about 10% of body weight over the same period.
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What each diet actually looked like
The three assigned menus were built around very different macronutrient targets. Participants received all of their food from the research team and met weekly with a dietitian to help them stick to the plan.
Diet | Carbohydrates | Fat Also read: Your nightly melatonin may come with a heart risk most users never expect |
|---|---|---|
Ketogenic | 4% | 73% |
Mediterranean Also read: Waking briefly at night in middle age may be a hidden early clue to Alzheimer's risk | 50% | 35% |
Plant-forward | 70% Also read: Your gut bacteria may be quietly shaping how strong you are | 15% |
In practice, a keto day for these participants meant eggs, meat, fish, cheese, nuts, oils, and non-starchy vegetables, with almost no bread, rice, pasta, fruit, or legumes. First author Max Petersen, an endocrinologist at Washington University, told ScienceAlert that a keto diet is very different from a typical American plate because "carbs are present in many other foods, including foods generally recognized as healthy such as starchy vegetables, fruits, and legumes."
What the researchers think is happening
When the team tracked blood samples across a 24-hour period, the keto group showed the largest increase in glucagon, a hormone that helps clear fat out of the liver, and the biggest drop in blood insulin. That combination points to a metabolic shift beyond simple calorie cutting.
Corresponding author Samuel Klein said in the press release that "our data suggest that if you have high liver fat content and prediabetes, reducing carbohydrate intake can have important therapeutic effects on metabolism beyond just weight loss alone."
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One concern going in was cholesterol. A diet that gets nearly three quarters of its calories from fat could, in theory, push LDL levels higher. That did not happen here. Petersen said "the most surprising finding was that participants in the ketogenic diet group didn't experience an increase in blood fat or cholesterol levels despite consuming the most fat."
The limits of a 42-person trial
The study is small. With 42 participants split across three arms, the researchers acknowledged that a larger trial might have picked up differences their sample was too small to see. It is also unclear whether a less strict low-carb pattern, one that does not push the body into full ketosis, would deliver the same liver and blood-sugar benefits.
Sustainability matters too. Participants ate food prepared by the research team for the full four to five months, which is very different from cooking keto meals in a normal household week after week. The findings apply to adults who had all three conditions studied, meaning obesity, prediabetes, and fatty liver, not to the general population.
Prediabetes itself is widespread. The CDC estimates that 115.2 million US adults have it, and 8 in 10 do not know. Anyone considering a major dietary change to address prediabetes or fatty liver should talk with a doctor first, particularly if they take medication for blood sugar, blood pressure, or cholesterol. The full study is available in Cell Metabolism (DOI: 10.1016/j.cmet.2026.07.020).
This article is made and published by Jesper Bengtson, who may have used AI in the preparation.