Today, we look at a potential ‘holy grail’ approach to sports nutrition for endurance athletes: The Keto:High Carb periodised diet.

As mentioned last week, ketogenic diets improve the ability of the muscle to use fat for fuel (nearly unlimited fuel) and have less reliance on carbohydrates (limited fuel).

We concluded that keto diets do have utility for ultra-ultra-endurance athletes competing at a low to moderate intensity.

Reason being is that we can use fat for fuel at a higher rate and not run out, although this is at the expense of nearly depleted carbohydrate stores.

Therefore, any form of high intensity work will become massively compromised as carbohydrates are the primary source for fuelling. Since Keto diets comprise of <50g of carbs/day, this isn’t a wise approach for high intensity scenarios.

The question is, can we get the best of both worlds? I.e. having the ability to use fat for fuel (unlimited supply) at a very high rate, but still have carbohydrates in the muscle readily available for high intensity efforts?

This is where the keto:high carb periodised diet comes in.
The aim is to follow a ketogenic diet during the training block to become ‘fat adapted’, but reintroduce carbohydrates right before an event to load the muscle and race under high carbohydrate availability.

Sounds pretty sweet! But not so fast…

One issue with going low/no carbohydrate is that you get a downregulation in enzymes responsible for breaking down glycogen for fuel. I.e. you may be able to replenish the stores in the muscle, but you can’t utilise them – this then compromises performance at higher intensities.

Knowing this, the potential ‘best of both worlds’ couldn’t be accomplished in some studies where they had a shorter fat adaptation period (under 4 weeks).

But wait…there’s more!

One case study (Webster et al, 2018) periodically introduced carbs with an ultra-endurance athlete after 2 years of keto-adaptation. They found that he was able to utilise the carbohydrates stores in the muscle whilst being able to burn fat for fuel at a high rate – i.e. the best of both as he was still able to perform at higher intensities.

By all means, this is not conclusive in the slightest (only seen in 1 person) and I wouldn’t advocate that every ultra-athlete goes on a long term keto diet. However, there may be some utility in this periodised approach.

In that sense…to be continued.

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