A randomized clinical trial published August 27, 2026 in Cell Metabolism assigned adults with obesity, prediabetes and fatty liver disease to one of three eating plans for about five months.
All three groups lost roughly 10 percent of their body weight. But the keto group cut liver fat by 67 percent, compared with 45 percent on both the Mediterranean and a mostly plant-based low-fat plan.
The trial, led by researchers at Washington University School of Medicine in St. Louis, enrolled 55 volunteers with what the team called metabolically unhealthy obesity. Forty-two completed the intervention.
Why liver fat matters even when the scale moves
Fat lodged in the liver is a marker of metabolic disease that runs alongside weight, not just under it. Left unchecked, the buildup can progress to inflammation, scarring and cirrhosis.
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Metabolic dysfunction-associated steatotic liver disease, known as MASLD, is now the most common chronic liver condition in the country. It affected an estimated 32.5 percent of US adults in the most recent national survey.
Two people can lose the same amount of weight and end up in very different places in the liver. Doctors have described several subtle clues that can point to fatty liver disease long before any diagnosis.
What the three diets looked like
The plans were designed to differ sharply in macronutrients. The ketogenic diet delivered 4 percent of calories from carbohydrates and 73 percent from fat.
The Mediterranean diet provided 50 percent from carbohydrates and 35 percent from fat. The plant-forward low-fat plan was built on 70 percent carbohydrates and 15 percent fat.
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Blood sugar responses tracked the same pattern as liver fat. Around-the-clock glucose fell by 20 percent on keto and by about 8 percent on the other two diets.
Fasting insulin dropped by 74 percent in the ketogenic group, compared with 44 percent on the Mediterranean plan and 27 percent on the low-fat plan.
Half of the keto participants no longer met the threshold for prediabetes at the end of the trial. In the Mediterranean group, 29 percent achieved remission. On the low-fat plan, 7 percent did.
Fat on the plate did not raise fat in the blood
One outcome caught the researchers off guard. "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," said first author Max C. Petersen, an assistant professor of medicine at Washington University School of Medicine. Senior author Samuel Klein has framed the wider takeaway around a metabolic effect from cutting carbohydrates that reaches beyond the weight lost, in people with high liver fat and prediabetes.
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The trial has limits. Only 42 people finished, the follow-up covered roughly five months, and the results apply to a diet strict enough to produce ketosis, not a casual low-carb approach.
The authors also note the Mediterranean plan preserved muscle and bone mass better than keto, an aspect that could matter over the long haul. Scientific American reported that outside experts urged caution about extrapolating the metabolic wins to a permanent way of eating.
Anyone with prediabetes or a fatty liver diagnosis who wants to try a strict low-carb approach should raise it with their doctor first. Blood sugar and blood pressure medication doses often need adjustment as diet changes.
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This article is made and published by Jesper Bengtson, who may have used AI in the preparation.