Episode 103 - What is exogenous carbohydrate oxidation testing, and how would it benefit me? | Dr Tim Podlogar & Prof Gareth Wallis

In the past decade, we've gone from low carb to high carb. Are we now heading towards a new era of personalised carb? In this episode I speak to two experts about exactly what exogenous carbohydrate oxidation is, how the testing works, who might benefit from this type of testing, and how to interpret the results.

Timestamps:

04:09 - Tim and Gareth's background and research

10:50 - What is exogenous carbohydrate oxidation?

11:41 - How do you test exogenous carbohydrate oxidation rate?

16:26 - How should an athlete prepare for exogenous oxidation testing?

19:10 - The importance of doing the test properly

22:50 - Are we testing maximal oxidation capacity, or replicating race conditions?

23:44 - What's the real-world benefit of exogenous carbohydrate oxidation testing?

28:17 - Making this testing available to athletes

33:58 - Assumptions, caveats and limitations to exogenous oxidation testing

37:33 - The difference between relative and absolute exercise intensity - does it matter here?

40:52 - What happens when you overfeed carbohydrate during exercise

43:59 - Why Tim and Gareth only test for glucose (and not fructose) oxidation

47:13 - How carb intake recommendations are made based on test results

50:58 - Can you improve exogenous oxidation through exercise or gut training?

57:26 - The (very) high carb trend - will testing help prevent unnecessary carb intake?

1:00:48 - Who might benefit most from testing, and do gut issues predict oxidation abiilty?

1:07:35 - Unanswered questions in this area

1:10:37 - Bonus Round

1:13:42 - Summary, unanswered questions and wrap up

 

Research mentioned in this episode:

Podlogar T, Cooper-Smith N, Gonzalez JT, Wallis GA. (2025). Personalised carbohydrate feeding during exercise based on exogenous glucose oxidation: a proof-of-concept study. Performance Nutrition. 1:2. doi: 10.1186/s44410-025-00003-9

 

Dr Tim Podlogar:

University of Exeter: experts.exeter.ac.uk/43996-tim-podlogar

Instagram: @tpodlogar

LinkedIn: linkedin.com/in/timpodlogar

 

Prof Gareth Wallis:

University of Birmingham: birmingham.ac.uk/staff/profiles/sportex/wallis-gareth

LinkedIn: linkedin.com/in/gareth-wallis-8291a441/

Oxidation testing service (Fuel Sync) coming in Jan 2026

 

Fueling Endurance eBook | T -12 Race Nutrition Course | Practitioner Resources

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