Ketogenic Diet Cut Liver Fat by 67% in a 12-Week Study

The ketogenic diet reduced liver fat more than low-fat and Mediterranean diets in a 12-week trial, even though participants in all three groups lost about the same amount of weight. That difference suggests carbohydrate intake may affect metabolic health apart from the effects of weight loss, at least for adults with obesity, prediabetes and fatty liver disease. The finding is striking, but the study’s small size and short duration limit what it can establish.

Similar weight loss, different liver fat results

Researchers randomly assigned 42 adults with obesity, prediabetes and fatty liver disease to a low-carbohydrate ketogenic diet, a low-fat diet or a Mediterranean diet. They supplied participants with food and held regular meetings to support adherence, giving the researchers more control over what people ate than they’d have in a typical free-living study. That support helps make the diet comparison more meaningful, though it also leaves open how easily participants could follow the plans without that structure.

The ketogenic group’s liver fat fell by an average of 67%. The low-fat and Mediterranean groups each saw reductions of about 45%. All three groups lost roughly 10% of their body weight, making the gap in liver fat reduction notable: the groups experienced similar weight loss, but their liver fat measurements changed by different amounts. This is more significant than it looks, because it challenges the simple assumption that comparable weight loss will always produce comparable changes in every measure of metabolic health.

The ketogenic plan derived just 4% of its calories from carbohydrates. Participants on it also nearly doubled the improvement seen in the other groups in the share who no longer met the criteria for prediabetes. That result points in the same direction as the liver fat finding, though the report doesn’t establish whether the diet itself, the degree of carbohydrate restriction or another part of the intervention explains the difference. A 12-week trial can identify a signal; it can’t settle how durable that signal is.

Hormonal changes and cholesterol findings

The study, published in Cell Reports Medicine, found that low-carbohydrate diets produced the largest rise in glucagon, a hormone involved in breaking down stored liver fat. The ketogenic diet also led to the largest drop in blood insulin. These changes offer a possible physiological explanation for why liver fat fell more in that group, but the reported results don’t show that the hormone shifts caused the difference. Here’s the thing: a plausible mechanism is useful, but it’s still an interpretation of the findings.

“The most surprising finding was that participants in the ketogenic diet group didn’t experience an increase in blood fat or cholesterol levels,” said Max Petersen, the study’s first author at Washington University School of Medicine. “Despite consuming the most fat.” That observation addresses a common concern about a high-fat diet, but it describes what happened in this particular group over a short trial. It shouldn’t be read as evidence that every person will have the same response or that longer-term effects are settled.

Corresponding author Samuel Klein said the results point to potential metabolic effects beyond those associated with weight loss. “Our data suggest that if you have high liver fat content and prediabetes, reducing carbohydrate intake can have important therapeutic effects on metabolism beyond just weight loss alone.” The wording is appropriately focused on people with those conditions. Whether the same benefits apply to other groups, or persist over time, remains unanswered by this study.

Diet alongside obesity treatment

The findings may help people consider how food choices fit with obesity treatment, including GLP-1 medications. Petersen said such drugs can produce significant weight loss, while the study suggests diet composition may offer additional benefits. That comparison raises a practical question: if weight loss is one goal, should treatment also account for outcomes such as liver fat and prediabetes status? The trial doesn’t test a combined approach, so it can’t say how diet and medication might work together.

If you're working in this space, the distinction matters: weight on the scale is only one measure of response. A diet that changes liver fat more despite similar weight loss could affect how clinicians and researchers assess metabolic outcomes, though this study alone isn’t enough to establish a preferred plan. And yet, the result is a reason to look more closely at diet composition, especially for people who match the trial’s participant profile.

What the trial can tell us next

The trial was small and lasted 12 weeks, so it offers a focused comparison rather than a long-term picture. Participants received food and regular support, conditions that may be difficult to reproduce in everyday life. The study also compares three dietary patterns as delivered in the trial; it doesn’t isolate every feature that might account for the differences.

Still, its central signal is clear: when weight loss was similar, the ketogenic group had the largest reduction in liver fat. The next question is whether that advantage lasts and how it relates to health outcomes beyond the measurements reported here. A promising result. Not a final answer.