September 1, 2026
This popular diet reduced liver fat by two-thirds and helped many participants overcome prediabetes
In a clinical trial, the ketogenic diet reduced liver fat by 67%, while half of the participants no longer met the criteria for prediabetes
ByAdrian Villellas
Editor
The bathroom scale was not the whole story in a randomized clinical trial published August 27, 2026. Adults with obesity, prediabetes, and fatty liver disease lost about 10% of their starting weight on ketogenic, Mediterranean, or very-low-fat eating plans
Yet the keto group reduced liver fat by an average of 67% from baseline, compared with 45% in each of the other groups
About half of participants who completed keto also no longer met the blood sugar criteria for prediabetes after roughly four to five months
Still, this was a small, short study in a narrowly defined group, not proof that keto is the healthiest diet for everyone. What people ate appeared to matter even after researchers made weight loss roughly equal
A fairer test of three diets
Most diet comparisons have a built-in problem. One group may lose more weight, making it hard to tell whether better health markers came from the eating plan or simply from shedding more pounds
This trial tried to hold that part of the contest steady. A federal estimate covering August 2021 through August 2023 found that 40.3% of U.S. adults had obesity
“Weight loss induced by a very low-carbohydrate diet provides additional therapeutic effects on glucose and lipid metabolism,” said senior author Samuel Klein of Washington University School of Medicine (WashU Medicine) in St. Louis. Lipid metabolism is simply how the body processes, stores, and moves fats
First author Max C. Petersen helped lead the trial. The team randomly assigned 55 adults, and 42 completed the study, with 14 in each group
Researchers supplied every meal and snack, and participants met with a dietitian each week. Keto provided 4% of calories from carbohydrates, 73% from fat, and 23% from protein
The Mediterranean plan, which emphasized foods such as vegetables, olive oil, nuts, fish, and dairy, supplied 50% from carbohydrates and 35% from fat
The plant-forward plan, built mostly around plant foods, supplied 70% of calories from carbohydrates and 15% from fat, while protein provided the remaining 15% in both higher-carbohydrate groups
Calories were adjusted until each group lost about one-tenth of its starting weight. That took around four to five months
Liver fat moved in a different direction
Body fat dropped with every eating plan, but the liver showed the clearest split. Measured liver fat fell by 67% in the keto group and 45% in both higher-carbohydrate groups
Liver insulin sensitivity, meaning how well the organ responds to insulin, improved roughly two to three times as much with keto
Fatty liver disease, now often called metabolic dysfunction-associated steatotic liver disease, means excess fat has collected inside the liver. Think of the organ as a traffic controller for fuel
When it stops responding properly to insulin, it may keep releasing glucose even when the body is signaling that enough is already circulating
Average glucose exposure over 24 hours fell by 20% on keto, compared with 8% on each of the other diets. Daily insulin exposure fell by 74% on keto, 44% on the Mediterranean plan, and 27% on the low-fat, plant-forward plan. Those figures suggest the pancreas needed to send out less insulin to manage blood sugar
A ketogenic diet restricts carbohydrates so sharply that the body leans more heavily on fat and ketones for fuel. The keto group also had the largest rise in glucagon, a hormone that can encourage the liver to break down stored fat
But the study cannot pin every difference on carbohydrates alone because the keto plan also contained more protein and a very different mix of foods
Prediabetes improved most on keto
Prediabetes means blood sugar is higher than normal but not yet high enough for a type 2 diabetes diagnosis. At the end of the intervention, 50% of the keto group no longer met its criteria
The figure was 29% with the Mediterranean diet and 7% with the plant-forward diet, though the study did not establish whether those changes would last
Weight loss remained the biggest shared winner. Muscle cells became roughly 50% more responsive to insulin, the hormone that helps move sugar out of the blood, in all three groups
That suggests losing weight drove many of the benefits no matter whether the plate held more fat or more carbohydrates. Keto did not win every category
High fat did not settle the heart question
Despite getting nearly three-quarters of its calories from fat, including about 23% from saturated fat, the keto group did not end the trial with significantly different LDL cholesterol, apolipoprotein B, or total 24-hour triglyceride exposure compared with the other groups. Apolipoprotein B is a marker of cholesterol-carrying particles linked to cardiovascular risk
Interesting? Yes, but it is not a long-term safety verdict. The trial measured risk markers during active weight loss, not heart attacks, strokes, liver scarring, or what happened after participants returned to everyday eating
Only 42 people completed the intervention, and the researchers supplied all food along with weekly professional support. That is closer to having a nutrition team run your kitchen than figuring out dinner after a long day. The findings also apply most directly to adults with obesity, prediabetes, and fatty liver disease
Researchers do not yet know whether milder carbohydrate restriction would deliver the same liver benefit or whether keto would keep its advantage during weight maintenance
Longer Mediterranean diet research has measured cardiovascular events over several years, while a separate 12-month randomized trial found that both a plant-forward low-carbohydrate plan and a healthy Nordic diet reduced liver fat compared with usual care. That is a reminder that food quality matters too
What this means in real life
The fairest takeaway is narrow. For people who closely match the trial group, a supervised ketogenic diet may offer added short-term help for liver fat and blood sugar control while they lose weight. The word “may” matters
Larger studies need to test whether the benefits last, whether people can maintain the plan without supplied meals, and how it affects cardiovascular health over years
The National Institutes of Health and the Foundation for Barnes-Jewish Hospital supported the work
The full study was published in Cell Metabolism
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