Extra body weight is a risk factor for high blood sugar and fat buildup in the liver, which can impair function and cause inflammation. Now, researchers may have found a specific diet that can help.

A recent study published in Cell Metabolism found that people with obesity who followed the ketogenic—commonly known as keto—diet, which is a low-carbohydrate and high-fat eating plan, saw more drastic improvements in liver and blood sugar measures than those on other popular diets, including the Mediterranean.1

However, experts don’t advise switching to the keto diet just yet. Here’s why.

Putting Three Diets to the Test

To test which eating plan was best for metabolic markers like blood sugar and liver function, researchers recruited dozens of people with metabolically unhealthy obesity, meaning they had excess liver fat and were prediabetic.

They then randomly divided participants into three diet groups: keto, Mediterranean, and low-fat, plant forward. Participants were instructed to meet with a dietitian and eat a certain amount of prepared food provided throughout the five-month study.

Here’s the percentage of daily calories coming from carbs, fat, and protein in each diet:

• Keto: 4% (20 grams) of carbs, 74% (164 grams) of fat, 23% (112 grams) of protein
• Mediterranean: 50% (254 grams) of carbs, 35% (80 grams) of fat, 15% (83 grams) of protein
• Low-fat, plant-forward: 70% (352 grams) of carbs, 15% (35 grams) of fat, 15% (90 grams) of protein

Researchers took blood samples before and after participants lost about 10% of their body weight.

Keto Diet Beats Out the Others

All participants saw metabolic improvements and lost weight, but the keto group appeared to lose weight the fastest. Participants lost 10% of their body weight after about 4.6 months on the keto diet, compared to 5.1 months on the low-fat, plant-forward diet and 5.4 months on the Mediterranean diet.

Similarly, the keto diet stood out for improving insulin sensitivity and lowering blood glucose levels. Half of the keto participants reversed their prediabetes, whereas only 29% in the Mediterranean group and 7% in the plant-forward diet had that result.

Liver fat was reduced by 67% in the keto group and 45% in both the other groups.

What Could Be Behind the Outcome?

Experts said the keto diet’s stronger results could have come down to one thing: just how few carbohydrates people consumed on the diet.

“It makes sense that you would have better insulin sensitivity and see better glucose metabolism when there is so little carbohydrate to metabolize,” said Gillian Goddard, MD, an endocrinologist and adjunct assistant professor at NYU Grossman School of Medicine who wasn’t involved in the research.

“There’s no stimulus of the pancreas to produce insulin with that little carbohydrate being consumed, so the results were not surprising,” she added.

Plus, the dramatic drop in blood glucose and insulin that can come with eating fewer carbs has knock-on effects for the liver. Instead of making and storing fat, the liver was likely breaking it down and burning it, said Rachele Pojednic, PhD, EdM, FACSM, a nutrition scientist and chief science officer at Restore Hyper Wellness, who also did not participate in the study.

So, Should You Try the Keto Diet?

Before you switch to a keto diet, experts say there are some real drawbacks to both the new research and the diet itself to keep in mind.

The study was small, with only 42 participants completing it, and it was relatively short, with the final blood test coming just a few weeks after the study ended. “That’s not nearly long enough to know whether these changes last, especially since past research shows that low-carb diets’ advantages over other diets’ shrink over time,” Pojednic pointed out.

Another downside was the reliance on the pre-made food. While on the one hand, it allowed for better diet adherence and more accurate data, it also meant that how the participants ate wasn’t very reflective of how people eat in the real world, Goddard explained.

“The participants didn’t have to shop for and prepare food consistent with these diets, so they didn’t have to be making food decisions as part of this study,” she said.

Beyond the study limitations, the keto diet comes with notable downsides.

It’s very restrictive, making it difficult for people to stick with over time, Pojednic noted. The diet has also been criticized for its focus on fat, since eating a lot of foods high in saturated fat can worsen heart health over time.2 And unlike the Mediterranean and other plant-forward diets, keto doesn’t emphasize fruits, vegetables, and whole grains, which are important parts of a healthy diet.

That’s why Goddard wouldn’t jump to the keto diet based on this study alone. Instead, she said, the bulk of the evidence points to the Mediterranean as the best for overall health.

“It doesn’t come out looking amazing here,” she said, “but if we look at the global literature on healthy eating, the Mediterranean diet comes out ahead over and over again.”