The Science of Fuelling: Inside the Carbohydrate Performance Paradigm

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Jun 30, 2025

Jamie Whitfield, a Senior Lecturer at Australian Catholic University, dives into the evolving role of carbohydrates in endurance performance. He discusses the shift from fat adaptation to maximizing carbohydrate intake, explaining its efficiency as a fuel source. Jamie details how elite athletes consume 90 to 120 grams of carbs per hour and the necessity of 'gut training' to manage this intake. He also explores types of carbs, personalized nutrition strategies, and the implications for both elite and recreational athletes looking to optimize their performance.

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INSIGHT

Carbs Are More Oxygen-Efficient Fuel

Paradigm shifted from conserving carbs to maximizing carbohydrate use for endurance performance.
Carbs are more oxygen-efficient fuel than fats, giving a performance edge at high intensities.

INSIGHT

Oxygen Cost Differences Between Fuels

Carbohydrate oxidation produces ATP more efficiently than fat, consuming less oxygen.
This oxygen efficiency translates to measurable performance benefits, especially at high intensities.

INSIGHT

4-7% Oxygen Efficiency Gain

Using 100% carbs instead of fats can improve oxygen efficiency by 4-7%, a significant competitive advantage.
This efficiency gain differs from improvements like supershoes but still meaningfully impacts performance.

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Carbohydrates have always been part of the endurance equation—but how much, when, and which types remain hotly debated. In this listener-driven episode, we tackle those questions and more, exploring a new paradigm in performance fueling that’s reshaping how athletes think about energy during exercise. Dr. Jamie Whitfield, Senior Lecturer at Australian Catholic University’s Mary MacKillop Institute for Health Research, joins us to break it all down.

For years, endurance athletes were trained to conserve carbs by becoming better fat-burners—adapting diet, training, and supplements to spare glycogen. But that thinking is evolving. As Jamie explains, the focus now is on maximizing carbohydrate use. Why? Because carbs are a more oxygen-efficient fuel source than fat—providing more energy per unit of oxygen. That efficiency improvement is a performance advantage in itself—like a supershoe, but internal.

We dig into how elite athletes are pushing 90 to 120 grams of carbs per hour, and what it takes to train the gut to handle it. Are there limits? What happens when intake exceeds demand? Where does the glucose go? Are there health risks? We also explore carb types and ratios, strategies for carrying fuel without excess weight, and how to tailor intake to your individual needs.

Jamie brings clarity to the technical details, helping translate complexity into actionable insight. If you’re fueling training or racing, this episode will reshape your approach to performance nutrition—and maybe your results too.

Show notes and links

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The Podlogar paper that compared 90g/h to 120g/h, informing some of our discussion
The Jeukendrup study Jamie mentioned that managed to provide 144g/h of carbs with a glucose-fructose mix
one of the studies mentioned in which glucose ingested spared liver glycogen use during exercise
A study that looked at performance and tolerance of carb solutions with different ratios of glucose to fructose

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