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The Keto Study That Wasn't About Keto | Dr Nicola Guess

October 19, 2026

AI Summary

5 min read

The High-Protein Diet That Wasn't Really About Ketones

When roughly one in three adults now carry excess fat in their liver—often without knowing it—the question of what to do about it becomes urgent. A new study from Sam Klein's group at Washington University seemed to give a clear answer: a ketogenic diet cut liver fat by 67%, far more than a Mediterranean diet or a plant-rich diet. But dietitian Dr Nicola Guess sees something different in the data. "I wouldn't call this a ketogenic diet," she says. "I think a better characterization is a high protein, low carbohydrate diet."

Why This Study Was Different

Most diet trials suffer from a fundamental problem: people don't follow the diets they're assigned. A meta-analysis of low-carb trials found that participants told to eat under 50 grams of carbs daily were often eating 180 grams by the end. "You're not testing what happens when people have less than 50 grams of carb a day," Guess explains. "You're testing what happens when you advise people to have less than 50 grams a day."

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What you'll learn

  • 1 (00:03) **The Clinical Question** - Setting up the problem: one in three adults has excess liver fat, often with drifting biomarkers, and patients want to know what diet can do beyond weight loss.
  • 2 (05:31) **The Headline Result and Its Misinterpretation** - The keto diet (23% saturated fat) cut liver fat by 67%, more than Mediterranean or plant-rich diets, but the "keto is best" take is misleading.
  • 3 (08:10) **Why Liver Fat Matters** - Liver fat is causally linked to insulin resistance and is a marker of unhealthy metabolism, regardless of the exact mechanism.
  • 4 (12:35) **Where Does Liver Fat Come From?** - The sources are dietary fat, adipose tissue, or de novo lipogenesis from carbs, but the answer depends on the individual and is difficult to study.
  • 5 (13:55) **The Protein Hypothesis** - Nicola interprets the entire literature as showing that protein, not carb restriction alone, is the key driver of liver fat reduction.
  • 6 (17:00) **The CarbFun Trial Confirms Protein's Role** - A large Norwegian trial with matched protein (16-17% calories) across different carb levels found no difference in liver fat, supporting that protein is the active variable.
  • 7 (19:13) **Study Design and Unreported Outcomes** - The study compared a high-protein low-carb diet (called "ketogenic") against plant-forward and Mediterranean diets, all with 10% weight loss.

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Show Notes

Practising registered dietitian and senior research fellow at the University of Oxford, Dr Nicola Guess, returns to the show to discuss a new study whose findings were interpreted in quite different ways the week it came out. Dr Samuel Klein’s group at Washington University assigned people with prediabetes to one of three diets, carefully controlled their weight loss, and found that the arm labelled ketogenic reduced liver fat by 67%.

Nicola’s view is that the label, and the conclusion many drew from it, deserve a closer look. Ketone levels in that arm were lower than you would typically expect on a ketogenic diet, which suggests something other than ketosis may explain the result. Her reading is that protein intake, rather than carbohydrate restriction, could be the more important variable. With roughly one in three adults carrying excess fat in the liver, often without symptoms, understanding what actually drives that reduction matters for the advice people receive.

What We Cover

  • Why this trial should not have been called a ketogenic diet study
  • How protein appears to lower liver fat even in the absence of weight loss
  • The 23% saturated fat arm, and why ApoB fell anyway
  • What likely changes once people move from weight loss into maintenance
  • Whether liver fat causes insulin resistance or simply marks it
  • Nicola's 35 grams of protein per meal target and how she builds a plate around it
  • Where seed oils and fibre actually sit in the evidence

This is a good example of why the label on a study matters as much as its headline number. If you have been told to cut carbohydrates to fix your liver, this conversation is worth your time.

To connect with Nicola Guess, visit NicolaGuess.com or find her on Instagram and YouTube.

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