Ketogenic Diet Outpaced Mediterranean and Low-Fat Plans on Liver Fat Reduction
A ketogenic diet produced the largest metabolic gains in a randomized clinical trial of adults with obesity, prediabetes, and fatty liver disease, cutting liver fat by an average of 67% over about four to five months. The same trial found that roughly half of the participants assigned to keto no longer met criteria for prediabetes by the end of the intervention.
All three diet groups lost about 10% of body weight, yet the liver responded differently depending on macronutrient composition. Weight loss mattered, but the carbohydrate restriction built into keto appears to have driven additional changes in hepatic metabolism that were not seen to the same degree with a Mediterranean diet or a low-fat, plant-forward diet.
Similar Weight Loss, Different Hepatic Biology
Researchers enrolled 42 people with obesity, prediabetes, and fatty liver disease and randomly assigned them to one of three eating patterns. Every participant received food, and weekly meetings with a dietitian were built into the protocol to support adherence. The calorie prescriptions were adjusted so that each group would lose about 10% of body weight, allowing the trial to isolate the effect of diet composition rather than the effect of weight loss alone.
The diets were sharply different in macronutrient profile. The ketogenic arm received just 4% of calories from carbohydrates and 73% from fat. The Mediterranean group received 50% of calories from carbohydrates and 35% from fat. The plant-forward, low-fat group received 70% of calories from carbohydrates and 15% from fat.
By the end of the intervention, body fat had fallen significantly across all three arms, and insulin sensitivity improved in each group. Those findings fit what clinicians expect when weight decreases in people with insulin resistance. The striking result came from the liver itself: despite matched weight loss, keto produced the steepest drop in hepatic fat.
Liver Fat Fell Most on Keto Despite Comparable Weight Loss
Liver fat declined by 67% in the ketogenic group, compared with 45% in both the Mediterranean and plant-forward groups. A difference of that size is clinically meaningful because excess hepatic fat is tightly linked to insulin resistance, impaired glucose handling, and the progression of metabolic dysfunction associated with fatty liver disease.
The mechanism likely extends beyond caloric deficit. During the 24-hour metabolic monitoring period, the keto group showed the largest rise in glucagon, a hormone that promotes mobilization of stored fuel and helps reduce fat accumulation in the liver. They also had the greatest decline in blood insulin levels. Lower insulin can reduce hepatic lipogenesis, the process by which the liver turns excess substrate into fat. In practical terms, a carbohydrate-restricted diet can shift the body away from storing fuel in the liver and toward using existing fat as energy.
The trial also addressed a concern that often shadows high-fat diets: whether blood lipids rise in parallel with fat intake. The biggest surprise was that participants in the ketogenic group did not experience an increase in blood fat or cholesterol levels despite consuming the most fat. That finding does not mean every patient will respond the same way, but it does show that the combination of calorie control and very low carbohydrate intake can produce a hepatic benefit without an obvious short-term lipid penalty in this cohort.
Prediabetes Reversed in About Half of the Keto Group
Glucose metabolism improved in all arms, yet the ketogenic diet produced the strongest shift out of the prediabetes range. About 50% of participants assigned to keto no longer met criteria for prediabetes after the intervention. The corresponding proportions were 29% for the Mediterranean diet and 7% for the plant-forward diet.
That gap matters at the bedside because prediabetes is not a static label; it reflects a high-risk metabolic state that can improve when insulin resistance falls. In this trial, the combination of weight loss and carbohydrate restriction appears to have pushed a larger share of participants across a clinically relevant threshold. For a patient with obesity, fatty liver disease, and prediabetes, the result suggests that macronutrient composition may determine whether metabolic improvement is modest or more complete.
The data also align with the physiology of fatty liver disease. When carbohydrate intake is sharply restricted, circulating insulin tends to fall, and the liver is less driven to synthesize and store triglycerides. Less hepatic fat can, in turn, improve hepatic insulin sensitivity and reduce the metabolic pressure that sustains prediabetes. The liver was not just losing fat; it was moving into a less insulin-resistant state.
What the Trial Can and Cannot Answer
Samuel Klein, the study’s corresponding author at Washington University School of Medicine in St. Louis, framed the findings around the idea that reducing carbohydrate intake may deliver metabolic benefits beyond weight loss alone in people with high liver fat and prediabetes. Max Petersen, the study’s first author, pointed to the contrast between diet composition and obesity pharmacotherapy, noting that GLP-1-based medications have changed weight-loss treatment while diet composition can still add benefits.
The trial was tightly controlled, but it was also small, with 42 participants. Food provision and dietitian support strengthened internal validity, yet the results still need confirmation in larger and more diverse populations, especially because long-term adherence to a ketogenic diet can be difficult in routine practice. The study also does not settle the question of durability beyond the four- to five-month window. Whether the liver-fat reduction and prediabetes reversal persist once the structured intervention ends remains untested here.
Even with those limits, the trial draws a sharp clinical line: when weight loss is held constant, a ketogenic diet can deliver larger short-term gains in liver fat and glucose status than either a Mediterranean or low-fat plant-forward approach in adults with obesity, prediabetes, and fatty liver disease.