Three diets, same weight loss. Different livers.

People say: “It doesn't matter how you lose weight” We read the study.

What they did

Randomised controlled trial (RCT). 55 people. ~5 months (to ~10% weight loss).

A trial. Chance decided who did what.

Who: Adults 18-55 with BMI 30-50, prediabetes and liver fat >=5% (no diabetes, premenopausal women); 42 completers, mean age 43, BMI 38.9; WashU St. Louis; NCT02706262

What they found
  • Muscle, every diet+50%
  • Liver fat on keto (others -45%)-67%
  • Liver insulin sensitivity2–3×
The catch

More to know, from our read of the paper:

  • Small: 55 randomized, 42 analysed (14 per arm)
  • No non-dieting control group
  • Short-term; no hard outcomes (diabetes, heart disease, death)
  • Keto arm also had more protein (23% vs 15%)
  • Obesity + prediabetes + fatty liver only
The verdict

Same weight loss. Keto did most for the liver.

One thing to try
  1. Losing weight helps anywayMuscle improved ~50% on every diet.
  2. Fatty liver? Low-carb did mostIn this trial. Ask your doctor.
  3. Mind the fine print5 months, 42 people. Long-term unknown.
In short

55 adults with obesity, prediabetes and fatty liver were randomly assigned keto, Mediterranean or very-low-fat, with all food provided until each lost about 10%. Muscle insulin sensitivity rose about 50% on every diet. But keto cut liver fat by 67% vs 45%, improved liver insulin sensitivity two to three times more, and 50% went into prediabetes remission (vs 29% and 7%). LDL cholesterol didn't differ. Small, short trial; keto also had more protein.

The video
The paper

Petersen et al. (2026). Effect of diet macronutrient content on the cardiometabolic response to weight loss: A randomized clinical trial. Cell Metabolism.

Design: Randomised controlled trial (RCT) · randomized trial comparing 3 diets (all food provided)

DOI: 10.1016/j.cmet.2026.07.020

Goals:

Eat better
How we checked

We read the abstract and the full text of this paper and checked every number on this page against it (15 facts, checked on 2026-09-27). The study design is named above. Cohort and other observational studies are described as linked, not proven. Found an error? Email theis@onestudyaday.com.

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