A ketogenic diet slashed liver fat by 67% in a controlled clinical trial — dramatically outperforming both Mediterranean and low-fat diets — even when all participants lost the same amount of weight, according to a study published August 27 in the journal Cell Metabolism.
The trial, led by Washington University School of Medicine in St. Louis, enrolled 42 participants with obesity, prediabetes, and fatty liver disease. They were randomly assigned to one of three diets: ketogenic (4% carbs, 73% fat), Mediterranean (50% carbs, 35% fat), or low-fat plant-forward (70% carbs, 15% fat). Researchers supplied all food and adjusted calories so every group lost roughly 10% of body weight over four to five months.
Despite identical weight loss, the metabolic outcomes diverged sharply. The ketogenic group achieved a 67% average reduction in liver fat, compared with 45% in both the Mediterranean and low-fat groups. The keto group also showed the largest rise in glucagon — a hormone that mobilizes stored liver fat — and the greatest drop in blood insulin levels.
"If you have high liver fat content and prediabetes, reducing carbohydrate intake can have important therapeutic effects on metabolism beyond just weight loss alone," said Samuel Klein, the study's corresponding author.
Perhaps most striking: about 50% of keto participants no longer qualified as prediabetic after the intervention, compared with 29% on the Mediterranean diet and just 7% on the low-fat plan. First author Max Petersen noted that the keto group did not experience increases in blood fat or cholesterol despite consuming the most fat of any group.
The researchers emphasized that while GLP-1 drugs have revolutionized obesity treatment, diet composition still matters. "The specific composition of the diet can give you added benefits," Petersen said.
The study was supported by the National Institutes of Health and the Foundation for Barnes-Jewish Hospital.
