Keto vs High-Carb for Marathon Training — What the Science Actually Shows
Runners are being told to cut carbs, train low, and rely more on fat adaptation without fully understanding what that does to performance at race pace.
There’s a lot of noise around low-carb and ketogenic approaches in endurance training, but when you look at the actual research and what happens at competitive intensities, the story changes quickly. In this video, I break down why carbohydrates are not optional for marathon performance, what’s actually happening at a physiological level when you run out of glycogen, and why fat and carbs are not interchangeable fuel sources once intensity rises.
I also walk through the research behind this debate, including findings from Project Supernova led by Louise Burke, where elite athletes showed a clear performance gap between carb-fuelled and keto-adapted approaches despite similar fitness gains. From there, we get into the practical side of fuelling: how many grams of carbohydrates you should be targeting per hour, why glucose and fructose ratios matter, how to train your gut properly, and what a realistic race-day fuelling strategy should actually look like.
This is the same framework I use with athletes across all levels, from first-time marathoners to sub-elite runners, to make sure they can sustain race pace when it matters. If you want to avoid the wall, maintain your pace late in the race, and actually convert your fitness into performance, your fuelling strategy needs to match the demands of the event.
Happy Training!
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Original Supernova Study:
https://pmc.ncbi.nlm.nih.gov/articles...
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Chapters:
00:00 - The Myth of Fat Adaptation
03:09 - Understanding Carbohydrate Needs for Endurance
05:48 - The Science Behind Low-Carb Diets
09:05 - Practical Race Day Nutrition Strategies
11:57 - Preparing for Race Day: Carb Loading and Timing
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