Ketogenic Diets Suck for Speed and Power

More data just in case you needed it as a brand new study has found some shocking conclusions (1).

They took 16 young men and women, and tested them over 4 days under:

1) a low carb condition of less than 50 grams per day and

2) a high carb diet at 6 -10 grams / kg/ day aka- carb jackpot!

The exercise testing was Wingates on a bike and the yo-yo test.  For Wingates -think of pedaling really fast, and then all of sudden some evil lab nerd drops the hammer on you by upping the resistance massively!   Within about 10 -20 seconds, it feels like your quads were replaced with concrete.    And no, the yo-yo test was not playing with yo-yos – it is an intermittent sprinting test.

The low carb keto group saw their power drop by 7% on Wingate test in addition to running 15% shorter distance on the yo yo test (1).

I can feel the keto krowd getting ready to pounce and cry.

“But these athletes were not keto adapted!”

To which I would agree, but how long do athletes need to be keto adapted?

Last I heard, the timeline keeps getting longer from a few weeks to a few months, now to a couple years.  I do agree that the chronic adaptations are different and may be beneficial; however, ketones for a bioenergetic standpoint cannot create ATP (cellular fuel) at a fast enough rate to compete with carbohydrates.  Plus we have metric piss-tons of data (techy terms) that carbs enhance performance.   Read these and weep, keto power posers (2-23).

Keep in mind that while your keto athletes are working their way through keto flu and adapting to the keto diet, based on this study and other data (24-28), they are losing speed and power!


There better be one hell of a payoff at the end of that keto power loss train to make up for the lost training time.

Maybe the keto approach is ok for very long duration athletes; but we can debate that one later.

In the meantime, I am going to have some carbZ to keep my power up both in myself and the athletes I coach.

Summary- Too Long, Did Not Read

Newsflash – removing the main fuel for anaerobic exercise (high intensity) is not good for performance.

If a power drop of 7% does not matter to you, keto until your eyeballs turn yellow as butter.

But if speed and power matter to you, carbZ are your friend.

Pass me the poptarts.

Dr Mike

PS- I did NOT say “keto sucks for everything,” just that it is not great for high intensity work.

Keto Power Poo Poo References

  1. Wroble KA, Trott MN, Schweitzer GG, Rahman RS, Kelly PV, Weiss EP. Low-carbohydrate, ketogenic diet impairs anaerobic exercise performance in exercise-trained women and men: a randomized-sequence crossover trial. The Journal of sports medicine and physical fitness. 2019;59(4):600-7.
  2. M. S. Athletics and football. London: Longman’s, Green, and Co; 1887.
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