Does the Ketogenic Diet and Running Mix?

The ketogenic diet is based on high fat intake followed by very low carbohydrate intake. This diet goes against what has been preached for decades. Common knowledge since the 1950’s has boasted that carbohydrates are the way to go, and that fat is bad for your health. In the same breath, this common knowledge blames high fat diets for obesity and diabetes – despite the glaring evidence that shows that sugar is to blame. Peoples of the first world have been expanding their waistlines ever since fast food and pop drinks loaded with sugar have been brought to the market.

Being a relatively new diet (in the sense of mass adoption), there is still much research to be done on it. However, the research that has been done is looking very promising. The University of Michigan has done a study (Third Exposure to a Reduced Carbohydrate Meal Lowers Evening Postprandial Insulin and GIP Responses and HOMA-IR Estimate of Insulin Resistance) that showed that by having three low carbohydrate meals per day, insulin resistance is reduced by at least 30%. This is fantastic news for those with diabetes or prediabetes – but how does this diet apply to runners?

Don’t Runners Need Carbohydrates?

The entire goal of the ketogenic diet is to switch to using fats as an energy source. We’ve all been told to carb-load pre-race, or to make sure to eat as much carb-rich foods when training to make sure to have ample energy. By using fats instead, this goes completely against that idea. The fact of the matter is that certain muscle fibers depend on carbohydrates to function at maximum performance – the fast twitch muscles.

When applying this to running, we need to keep in mind the two energy systems we have in place. The aerobic side and the anaerobic side. On the first end, we have the slow twitch muscles. On the latter end, we have the fast twitch muscles. This part is important.

With aerobic work, ketones from ketosis readily supply the muscles with the energy they need to perform to the max. With anaerobic work, glucose is needed due to the incredibly quick burst of energy it can supply.

To answer the question, runners only need carbohydrates when they do extended anaerobic work.

So Sprinters Shouldn’t Go Ketogenic?

No, anyone can go ketogenic. For sprinters, it just means they have to carb-load 20g-30g roughly a half hour to an hour before their training/race. As the body burns through the glucose very quickly when sprinting, the carb-load should have little affect on staying in ketosis. In fact, runners can do very well with the ketogenic diet as they can burn through stored glycogen with ease, keeping them in the state of ketosis.

Having done a fair amount of running on this diet myself, I can attest to the fact that even with a relatively high amount of carbohydrate intake I can return to ketosis very quickly. The quickest way to return is through sprinting.

When racing, this carb-load is very important for reaching maximum performance. However, if you run longer events that depend more on the aerobic side, this isn’t necessary.

Doesn’t the Ketogenic Diet Reduce Performance Overall?

The Journal of the International Society of Sports Medicine studied elite artistic gymnasts (Ketogenic Diet Does Not Affect Strength Performance in Elite Artistic Gymnasts) by putting them on a ketogenic diet to see how it affected their performance relative to their normal diet. These are athletes that require a ton of endurance and muscle strength to keep going.

They found that there was no difference.

What did change, however, was body composition. Body weight and body fat was reduced in the athletes while the performance was unaltered.

In the concluding statements of the paper:

Many coaches do not favorably accept the use of a ketogenic diet by their athletes, both due to the absence of knowledge of the effects of the LCKD [low carbohydrate ketogenic diet] and due to fear that the diet can rebound on the physical performance of the athlete. Unfortunately there are very few studies on the topic “ketogenic diet and exercise”, showing consistent methods and results. Those that reported negative effects of VLCKD [very-low carbohydrate ketogenic diet] on performance were only carried out for a time of up to 15 days; but a longer period of time is necessary in order to induce the keto-adaptation.

Due to the time necessary for the body to become fat adapted (it takes time to switch to an entirely new fuel source), a ton of studies have to be thrown out the window because they simply weren’t showing the athletes on ketosis – which is the whole point of the ketogenic diet.

Our data suggest that athletes who underwent a VLCKD with adequate protein intake lost weight and improved body composition without any negative changes in strength and power performance.

In Fact, Distance Runners Should Like This:

Those that run long distances such as a marathon or an ultramarathon dread the “wall”. The wall is a sudden fatigue caused by the liver and muscles being depleted of stored glycogen – this means that your body has to switch to fat burning for energy. Gels and foods help stave this ailment off for a period of time, but your body slowly burns through the glycogen faster than it can digest and replenish those supplements.

The switch to fat burning takes time. This is why the wall lasts for so long, but once you cross over you’re back to normal running. However, on a ketogenic diet you’ve already crossed this wall. You won’t suffer the fatigue caused by the loss of glycogen – there’s no glycogen to lose.

Even better is that the body works hard aerobically even without glucose. Ketones as a fuel source won’t cause your performance to suffer, and you’ll only have to worry about holding the pace, form, and confidence during the event. As you’ve already broke through the wall, you won’t have the loss of performance like you would for the time when you normally would have had to deal with the wall.

This may not seem like a long time overall, but the wall can drop confidence in yourself by stretches of near infinitesimal lengths which is hard to regain. When racing, this confidence is necessary to continue with the willpower to tackle any hills, turns, or even simply holding the pace. Even after cracking the wall, you might not regain that original mental momentum you had.

Distance runners who have to deal with the wall might want to consider this diet in the future.

Final Thoughts:

The ketogenic diet can pair well with athletes, especially those looking to lose weight. Runners can get a lot of benefit as body composition will improve faster than if they were on a typical diet. Having started the ketogenic diet myself whilst continuing to run, I myself know that my performance hasn’t been lost.

To summarize the important notes:

  • The ketogenic diet pairs well with those looking to lose weight.
  • Runners might need to carb-up if they are focusing on sprints.
  • This diet helps improve body composition.
  • There’s no wall.
  • It caters to distance runners incredibly well.

By training hard and carb-loading when necessary, your body will run like a well oiled machine, ready to take down the competition.

Bacon image courtesy of C. Bill under the Creative Commons Attribution-ShareAlike 2.0 Generic license.


Caleb Thompson is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com, Amazon.ca, and other Amazon stores worldwide.

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