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What Is Keto? How Does It Affect Training?

Updated: Jul 12, 2023

Following on from our last post on the truths, myths and misconceptions around carbs, we asked Justin Reid-Simms the question "What is keto? How does it affect training?"

What About Keto? Louise Burke has been at the forefront of Nutrition Research in endurance sports for many years through her work with the Australian Institute of Sport. In 2017, she published a study looking at fat adaptation in race walkers; you know those guys & girls who can walk a marathon faster than you can run one? Here’s what she found: “Low Carbohydrate, High Fat diet impairs exercise economy and negates the performance benefit from intensified training in elite race walkers.” Key points • Three weeks of intensified training and mild energy deficit in elite race walkers increases peak aerobic capacity independent of dietary support. • Adaptation to a ketogenic, low carbohydrate, high fat (LCHF) diet markedly increases rates of whole‐body fat oxidation during exercise in race walkers over a range of exercise intensities. • The increased rates of fat oxidation result in reduced economy (increased oxygen demand for a given speed) at velocities that translate to real‐life race performance in elite race walkers. • In contrast to training with diets providing chronic or periodised high carbohydrate availability, adaptation to an LCHF diet impairs performance in elite endurance athletes despite a significant improvement in peak aerobic capacity Although they improved their fat oxidation at all intensities, they lost their top gear. Potentially became less metabolically flexible (able to switch between carbs & fat for fuel) and subsequently their performance in a 10KM Time Trial was reduced. Take a peek below to see how the groups with Carbohydrates in their diet performed.

In terms of other relevant studies, here’s a quick summary of research results, that demonstrates why, as an endurance athlete, ketogenic diets may not be best for performance. The arrows show whether there was no change or a decrease in performance.

What does it all mean? Let’s talk about practicalities! Fletch & The Onetrack team had a couple of questions they wanted me to cover. We’ve already discussed why carbs have got a bad rep recently, and whether we need them to perform at our best. Having a quick background of the science involved should help you have a better understanding of how to manipulate your nutrition.

Justin Reid-Simms is a Certified Nutritionist, Onetrack Running Coach & Personal Trainer. Want to work with Justin? Enquire and book a consultation here

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