September 1, 2026
Keto diet delivers surprising health benefits beyond weight loss
A clinical trial compared three popular diets to find out whether what people eat matters even when weight loss is nearly identical
BySanjana Gajbhiye
Editor
People often judge a diet by one result: weight loss. But two people can lose the same amount and still see different changes in their blood sugar, liver, and insulin
The difference matters especially for people with obesity, prediabetes, and fatty liver disease
About 40% of American adults have obesity. This can raise the risk of type 2 diabetes and heart disease
A clinical trial compared three popular diets after similar weight loss. All three diets improved health, but the keto diet led to the biggest improvements in liver health and blood sugar
Why food choice matters
Prediabetes means blood sugar is higher than normal, but not high enough for a type 2 diabetes diagnosis. Fatty liver disease means too much fat has collected inside the liver
Both problems often appear with insulin resistance, when the body does not respond well to insulin. This hormone helps move sugar from the blood into cells
Samuel Klein is the corresponding author at Washington University School of Medicine in St. Louis
“We know weight loss can improve metabolic health in people who are obese,” Klein said
“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 author said metabolism describes how the body uses, stores, and releases energy
Three diets were tested
The trial included 42 adults. Every participant had obesity, prediabetes, and fatty liver disease
The ketogenic diet got only four percent of its calories from carbohydrates and 73% from fat. With so few carbohydrates, the body relied more on fat for energy
The Mediterranean diet got 50% of its calories from carbohydrates and 35% from fat. The plant-forward diet had more carbohydrates, at 70%, and less fat, at 15%
Both higher-carbohydrate diets included many plant foods. However, the plant-forward diet kept fat especially low
Meals stayed closely controlled
The researchers supplied every meal and snack. Participants also met with a dietitian each week
The team adjusted each person’s portions so everyone lost about 10% of their starting weight
Reaching that goal took about four to five months. Because the groups lost nearly the same amount, the team could compare the diets more fairly
Every diet brought benefits
All three groups lost body fat. Their bodies also became more sensitive to insulin
In simple terms, the muscles became better at taking sugar from the blood. Blood sugar and insulin levels also fell across all three groups
These shared changes show that weight loss itself brought important benefits. The clearest differences between the diets appeared in the liver
Keto changed liver health
Liver fat fell in every group, but it dropped most with the ketogenic diet. The average reduction was 67% with keto, compared with 45% for both of the other diets
The liver also became better at responding to insulin in all three groups. That improvement was two to three times greater in the keto group
Insulin normally tells the liver to slow its release of sugar into the blood. A stronger response can make blood sugar easier to control
The liver can also turn nutrients into new fat. That process slowed the most in the keto group
Blood sugar fell further
The team tracked blood sugar and hormones across a full day. Average blood sugar fell by 20% in the keto group, compared with eight percent in each of the other groups
Daily insulin levels also fell most with keto. The body maintained lower blood sugar levels while using much less insulin
The trial lasted only a few months, so it cannot show that the improvement in prediabetes will last
Blood fats did not rise
A high-fat diet can raise concerns about cholesterol and other fats in the blood
Max Petersen is the first author at Washington University School of Medicine in St. Louis
“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,” Petersen said
Changes in LDL cholesterol, often called bad cholesterol, were not clearly different among the groups. Fasting triglycerides, another common blood fat, fell most with keto
These results cover only a short period. They cannot show how the diet may affect heart health over many years
Medicines changed obesity care
Petersen also discussed newer GLP-1 medicines, which can help people achieve major weight loss
“GLP-1-based medications have revolutionized the therapy of obesity. We now have a very effective pharmacotherapy for achieving significant weight loss,” Petersen added
Pharmacotherapy simply means treatment with medicine
“But in addition, our study shows that the specific composition of the diet can give you added benefits.”
Those benefits appeared mainly in the liver and in measures tied to blood sugar control
Limitations of the study
The trial included only 42 people, so more people need to be studied
Larger trials may show different results or smaller differences between the diets
Every participant had obesity, prediabetes, and fatty liver disease. The findings may not apply to people without all three conditions
The researchers supplied all food and offered weekly support. People choosing and preparing their own meals may find these diets harder to follow
The trial did not show if people could stick with these diets for years. It also did not show if the health benefits would last that long
Keto showed short-term benefits
The trial does not show that one diet is best for everyone. It shows that equal weight loss can lead to different changes inside the body
The keto diet produced the biggest short-term drop in liver fat. It also led to the largest improvements in blood sugar control
Longer trials are needed to see if these benefits last in daily life
The study is published in the journal Cell Metabolism
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