The Claim

Ultra-endurance runners on a long-term low-carbohydrate, high-fat diet (10% carbohydrate, 70% fat) have a 2.3-fold higher peak fat oxidation rate (1.54 g/min) during maximal exercise than those on a high-carbohydrate diet (59% carbohydrate, 25% fat), which has a peak fat oxidation rate of 0.67 g/min.

Source: Metabolic characteristics of keto-adapted ultra-endurance runners.

What the research says

Supports is higher

Support is ahead, but a single strong opposing study can change this.

Supports
41score
Challenges
0score

These are independent scores, not a percentage. Higher-grade studies count more, so a single strong opposing study can outweigh several weaker ones.

Quantitative
1 study reviewed
In plain English

Ultra-endurance runners who eat a diet that is mostly fat and very low in carbohydrates burn fat at a rate 2.3 times higher during maximum effort than runners who eat a diet high in carbohydrates.

See the scientific wording

Ultra-endurance runners following a long-term low-carbohydrate, high-fat diet (10% carbohydrate, 70% fat) exhibit a 2.3-fold higher peak fat oxidation rate (1.54 g/min) during maximal exercise compared to those on a high-carbohydrate diet (59% carbohydrate, 25% fat) with a peak rate of 0.67 g/min, indicating a profound metabolic adaptation to fat utilization under extreme endurance conditions.

Why this might work

When a person eats very little carbohydrate for a long time, their body switches to burning fat as the main fuel. Muscle cells make more structures that burn fat, increase the number of transporters that bring fat into those structures, and turn off the system that prefers sugar. This allows the muscles to burn fat much faster even during intense exercise, without running out of energy.

Verified mechanismbased on 1 study

What the research says

1 study

  1. Study: Metabolic characteristics of keto-adapted ultra-endurance runners.

    Runners who ate mostly fat and very little carbs for years burned fat more than twice as fast during intense exercise than runners who ate mostly carbs, proving their bodies learned to use fat as their main fuel.

Score breakdown, mechanism chain, raw evidence, ideal studies needed & 1 supporting studies

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