Researchers at Washington University School of Medicine randomly assigned 55 people with obesity, prediabetes, and fatty liver disease to one of three diets for four to five months — ketogenic, Mediterranean, or a low-fat, plant-forward plan. The team provided all their food, and 42 people completed the trial. Samuel Klein and Max Petersen led the study, published August 27 in Cell Metabolism. All three groups lost about 10% of their body weight, but the ketogenic group saw liver fat drop 67%, versus 45% in the other two groups, and half of the keto group no longer had prediabetes afterward, compared with 29% on Mediterranean and 7% on the low-fat diet. Cholesterol markers didn't move differently between groups despite keto eating far more fat.

1. The Metabolic-Benefit Camp (Samuel Klein and Max Petersen, Washington University; Jeff Volek, Ohio State University)

Cutting carbs did something weight loss alone didn't.

Cutting carbs helped, separate from the weight loss. Klein says the data show that for people with high liver fat and prediabetes, "reducing carbohydrate intake can have important therapeutic effects on metabolism beyond just weight loss alone."

The cholesterol fear didn't show up. Petersen called it the most surprising result: the keto group ate the most fat and still didn't see their blood fat or cholesterol rise.

A longtime keto researcher says this is overdue vindication. Jeff Volek has studied low-carb diets for years and wasn't part of this trial. He said: "It is nice to see these researchers finally coming around on ketogenic diets, as the evidence has been strong for a long time."

2. The Sustainability Camp (Christopher Gardner, Stanford; Sai Das, Tufts)

Gardner's own trial says keto's extreme carb cut isn't worth it. Das says this one's too small and too short to prove otherwise.

Gardner ran the same matchup and keto came up short. His own randomized trial, published in 2022, found keto and Mediterranean diets controlled blood sugar equally well, but keto delivered less fiber and fewer vitamins, and people found it harder to stick with. His view: "There's no reason to restrict heart-healthy, quality carbohydrate foods above and beyond" what's actually needed.

Das calls it promising, not proof. Sai Das, a nutrition scientist at Tufts, said the liver and blood-sugar findings are "highly promising" but flagged the trial's "short timeline and small sample size" as reasons to hold off on bigger conclusions.

Keto came with a cost: more muscle and bone loss. Das also pointed out that Mediterranean-diet participants lost more body fat and preserved more muscle and bone than the keto group did.

3. The Genetics Camp (Alexa Barad, Stanford)

Your genes decide whether keto raises your cholesterol.

Genes decide who gets this cholesterol spike. In a separate analysis of the DIETFITS trial that Barad presented in July, the Stanford researcher found that people with a higher genetic burden of LDL-raising variants saw significantly bigger cholesterol jumps specifically on low-carb diets, while low-fat dieters didn't show the same pattern regardless of their genes.

Genetically at-risk people are extra sensitive to saturated fat. As carbs go down and fat goes up on a low-carb diet, their LDL responds much more to each gram of saturated fat than everyone else's does.

Barad won't say keto is safe or risky for everyone. She said "some individuals may be more sensitive to the LDL cholesterol-raising effects of saturated fat...because of their genetic background," and recommends people on low-carb diets lean on nuts, seeds, olive oil, and avocado over butter and fatty meat rather than assume the diet affects everyone the same way.

Where This Lands

Klein, Petersen, and Volek say the new trial proves cutting carbs helps the liver and blood sugar in ways weight loss alone can't, and that the cholesterol risk didn't materialize. Das says a 55-person trial with 42 completers over four to five months is too small and too short to settle anything long-term. Gardner's own earlier trial — a separate study, not a reaction to this one — found keto harder to sustain and nutritionally thinner than Mediterranean. Barad says genes, not diet choice alone, decide who's actually at risk.

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