A five-month randomized clinical trial found that a very-low-carbohydrate ketogenic diet produced greater reductions in liver fat and stronger improvements in some blood-sugar measures than Mediterranean and high-carbohydrate diets, despite similar weight loss.
A popular diet may offer benefits beyond weight loss for people with obesity, prediabetes and excess liver fat, according to a new clinical trial from researchers at Washington University School of Medicine in St. Louis.
The study, published in Cell Metabolism on August 27, 2026, compared three different weight-loss diets and found that participants following a ketogenic diet experienced a 67% reduction in liver fat after about five months. The other two diet groups saw reductions of about 45%.
The findings do not mean keto is universally better or that the diet cures prediabetes. The trial was relatively small and short, and the researchers emphasized that weight loss itself improved metabolic health across all three groups.
What did the new keto diet study find?
Researchers randomly assigned 55 adults with metabolically unhealthy obesity — meaning they had obesity along with prediabetes and excess liver fat — to one of three diets:
- A low-carbohydrate, high-fat ketogenic diet
- A Mediterranean diet
- A high-carbohydrate, low-fat, plant-forward diet
Participants received all of their food during the study and met weekly with a dietitian to help them follow their assigned eating pattern.
After approximately five months, participants in all three groups had lost about 10% of their starting body weight.
Muscle insulin sensitivity also improved by roughly 50% across all three groups, suggesting that the weight loss itself played a major role in improving muscle insulin resistance.
But researchers saw a different pattern when they looked specifically at the liver.
Keto reduced liver fat by 67%
The ketogenic group experienced a 67% reduction in liver fat, compared with about 45% in the Mediterranean and high-carbohydrate groups.
Researchers also found that liver insulin sensitivity improved two to three times more among people following the ketogenic diet than among those in the other groups.
That distinction matters because excess fat in the liver is closely associated with metabolic problems including insulin resistance, prediabetes and Type 2 diabetes.
The condition is commonly referred to as metabolic dysfunction-associated steatotic liver disease, or MASLD.
Blood sugar also improved more with keto
The ketogenic diet produced stronger changes in several measures of glucose metabolism.
According to the Washington University researchers, 24-hour blood glucose levels fell by about 20% in the ketogenic group, compared with about 8% in the other diet groups.
Average insulin levels also declined substantially more among participants following the low-carbohydrate diet.
Researchers reported a 74% reduction in circulating insulin levels in the ketogenic group, compared with 44% for the Mediterranean diet and 27% for the high-carbohydrate diet.
Did the keto diet reverse prediabetes?
One of the most attention-grabbing findings involved prediabetes.
By the end of the trial, 50% of participants in the ketogenic group no longer met the criteria for prediabetes.
That compared with:
- 29% in the Mediterranean diet group
- 7% in the high-carbohydrate, low-fat group
However, the finding should not be interpreted as proof that keto permanently reverses prediabetes for everyone.
The study involved only 55 people, lasted around five months and specifically enrolled adults with obesity, prediabetes and excess liver fat. More research is needed to determine whether the metabolic benefits continue over the long term.
Why might keto affect the liver differently?
The researchers believe the composition of the diet may influence certain metabolic processes beyond the effects of losing weight.
People in all three groups lost a similar amount of weight, but the ketogenic group experienced larger changes in liver insulin sensitivity and liver fat.
The study found that the ketogenic diet reduced the liver’s production of new fat, which may help explain why liver fat declined more substantially.
Researchers said future studies will need to investigate the biological mechanisms behind these additional effects.
Is keto better than the Mediterranean diet?
Not necessarily for every health outcome.
The trial showed that all three diets were beneficial for weight loss and overall metabolic health.
The ketogenic diet appeared to have an advantage for certain liver and blood-sugar measurements, but that does not automatically make it the best long-term eating pattern for everyone.
The Mediterranean diet has a broader body of evidence supporting cardiovascular and overall health, while very-low-carbohydrate ketogenic diets can be difficult to maintain and may not be appropriate for some people.
That’s why the study is better understood as evidence that the type of diet may matter for certain metabolic outcomes, rather than as proof that everyone should switch to keto.
What about keto for fatty liver?
The findings are particularly relevant to people who have obesity, prediabetes and excess liver fat.
The researchers said that weight loss is already known to improve metabolic health, but their results suggest that reducing carbohydrates may provide additional benefits for liver fat and liver insulin sensitivity.
Still, people with fatty liver disease should not assume that starting a strict ketogenic diet is automatically safe or appropriate.
Dietary needs can vary depending on a person’s medical history, medications and cardiovascular risk.
What happens after keto?
The Fox News article cited registered dietitian nutritionist Ilana Muhlstein, who suggested that keto could potentially be used as a short-term approach for some people with obesity or prediabetes, followed by a transition toward a Mediterranean-style diet for longer-term health.
That is an expert opinion rather than a treatment recommendation established by this single study.
The Washington University researchers themselves emphasized the importance of weight loss and said all three dietary approaches improved metabolic health.
The bottom line
The new study adds an important twist to the debate over popular diets.
Losing weight improved metabolic health regardless of which diet participants followed. But the ketogenic diet produced additional improvements in liver fat, liver insulin sensitivity and several measures of glucose control.
The biggest finding was the 67% reduction in liver fat among participants following the ketogenic diet, compared with about 45% among those following the other diets.
At the same time, the study was small and lasted only about five months. It therefore does not establish that keto is the best long-term diet for everyone or that it permanently reverses prediabetes.
For people considering major dietary changes, particularly those with diabetes, liver disease or cardiovascular risk, discussing the approach with a qualified health professional is important.
Study at a glance
| Finding | Keto | Mediterranean / high-carb diets |
|---|---|---|
| Weight loss | About 10% | About 10% |
| Liver-fat reduction | 67% | About 45% |
| Muscle insulin sensitivity | ~50% improvement | ~50% improvement |
| 24-hour glucose | 20% lower | About 8% lower |
| Prediabetes no longer present at study end | 50% | 29% Mediterranean; 7% high-carb |
