A very low-carbohydrate, high-fat ketogenic diet provides stronger metabolic benefits for adults with obesity than either a Mediterranean diet or a low-fat diet, according to a clinical trial published August 27 in the Cell Press journal Cell Metabolism. Researchers found that after four to five months of controlled eating, about half of the participants with obesity and prediabetes who followed the keto diet no longer met the clinical criteria for prediabetes.
How Popular Weight Loss Diets Compare on Liver Fat
An estimated 40% of adults in the United States have obesity. While doctors frequently recommend low-fat, low-carbohydrate, or Mediterranean diets to help patients lose weight, researchers have historically lacked clear data on whether one specific dietary pattern offers distinct metabolic advantages beyond simple weight reduction. To investigate this, Samuel Klein and his colleagues enrolled 42 participants diagnosed with obesity, prediabetes, and fatty liver disease.
The research team randomly assigned participants to one of three dietary regimens: a ketogenic diet, a Mediterranean diet, or a low-fat, plant-forward diet. To ensure strict compliance, the research team supplied all food, and participants met weekly with a dietitian. Calorie intake was individually adjusted so that every participant lost roughly 10% of their body weight, a milestone that took about four to five months to reach across all groups.
Did you know? While the ketogenic diet supplies roughly 73% of its calories from fat and only 4% from carbohydrates, the plant-forward diet derives up to 70% of its energy from carbohydrates and just 15% from fat. The Mediterranean group sits in the middle with 50% carbohydrates and 35% fat.
Ketogenic Diets Drive Greater Reductions in Liver Fat
Despite matching weight loss across all study arms, the ketogenic diet produced significantly more dramatic changes in liver and metabolic health. According to the trial data, liver fat plummeted by an average of 67% among participants following the keto diet. By comparison, liver fat fell by an average of 45% in both the Mediterranean and plant-forward groups.
Continuous 24-hour blood analyses revealed that participants on the ketogenic diet experienced the largest rise in glucagon, a hormone that actively helps clear stored fat from the liver. They also registered the sharpest drop in circulating blood insulin levels. “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,” says Max Petersen, the study’s first author at Washington University School of Medicine.
Reversing Prediabetes Through Specific Macronutrient Composition
The metabolic advantages of carbohydrate restriction extended directly to blood sugar regulation. Following the intervention, roughly 50% of participants on the ketogenic diet successfully reversed their prediabetes. That outcome contrasted sharply with the other groups: only 29% of participants on the Mediterranean diet and just 7% of those following the plant-forward diet achieved the same status.
“GLP-1-based medications have revolutionized the therapy of obesity. We now have a very effective pharmacotherapy for achieving significant weight loss,” Petersen notes. “But in addition, our study shows that the specific composition of the diet can give you added benefits.” The study received financial support from the National Institutes of Health and the Foundation for Barnes-Jewish Hospital.
Frequently Asked Questions
What percentage of calories come from fat on a keto diet?
Did participants on the keto diet experience high cholesterol?
No. Despite consuming a high-fat diet, participants in the ketogenic group did not show an increase in blood fat or cholesterol levels.
How much weight did study participants lose?
Researchers adjusted calorie intake so that participants in all three diet groups lost approximately 10% of their initial body weight over a four- to five-month period.
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