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Is It Safe To Train For A Big Race On The Keto Diet?

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Following the keto diet can be great for ultrarunners, but there is little studies on performance improvements. Is It Safe To Train For A Big Race On The Keto Diet? www.runnerclick.com

We have all heard about the infamous carb loading the night before a big race. But many runners have decided not to bring on the pasta, and instead cut off carbs almost completely even when fueling for a big race. More and more runners are following the keto diet.

The keto diet might be the new fad diet that is currently trendy, but it seems like everyone is trying it now. Even non-runners see real results without even exercising. This has people curious to try it out for themselves. Combine the diet with high-intensity workouts or running ,and followers really see results, shedding weight and losing inches.

But is it safe to train for a race as a runner on the keto diet? Won’t the runner burn out?

What Is The Keto Diet?

The ketogenic diet, or simply keto diet, is a strict low-carb, high-fat diet.

The science behind it can be a bit dense. But there is a method to the madness when it comes to becoming fat adapted and losing weight.

“The idea behind the keto diet is to almost eliminate carbohydrates from the diet to use fat as a source of fuel.” Jenna Gorham, RDN told Runner Click. “To do this the body must enter into a state of ketosis.”

And here is where biology comes in. “The keto diet is exceptionally low in carbohydrates, which are the body’s preferred source of fuel,” Gorham said. “Carbohydrates are the quickest source of energy because they are the easiest to breakdown and use for fuel.”

Without carbs, the body goes into the state of ketosis where it looks to its next fuel source which is fat. Ketosis is a natural process. The body basically goes into survival mode when its energy source is low, producing ketones from breaking down fats in the liver, which is used as energy.

By going into ketosis, the body is in its metabolic state, where more fat consumed equals more fat burned.

To Eat, What Not To Eat

What makes this diet stand out from other diets is the fact that is doesn’t even seem like a diet—minus the low carb, no sugar aspect. It has followers using lots of butter, putting cream in coffee and focusing on healthy fats.

Keto friendly meals include steak with vegetable dinners with a caesar salad no croutons, chicken bacon ranch casserole, or cheeseburger sans bun when at a barbecue.

For runners part of the Keto Runners! Facebook group, favorite meals include breakfast tacos that include eggs with avocado and bacon in cheese shells, cheese crust pizza, and “taco pie,” a taco crustless quiche.

Do not eat any starchy foods including whole grains, sweet potatoes, any kind of bread, pasta, and even most fruits because they are full of sugar. Non-fat milk and reduced-fat salad dressings are also a no-no because of its amount of carbs.

Photo credit: Pixabay

For coffee, use creamer, not milk. Or try bulletproof coffee that includes butter and MCT oil—just don’t drink it before a run since running to the bathroom is a strong possibility.

“Ketosis is actually quite hard for the average person to reach,” Gorham said. That is because it calls for being strict with the diet to always stay in ketosis. Even a small “cheat” meal can throw an entire day off.

Athletes, especially runners, need to be mindful of replenishing their electrolytes when deficient. Consume foods that are high in sodium, potassium, and magnesium, such as cured meats, cheeses, raw spinach, avocado, and use pink Himalayan salt.

For long runs (anything over 2 hours) and races, many keto runners use salts sticks, base salt, and electrolytes such as Nuun, UCAN hydrate or Ultima. Nut butter is another popular option.

One marathoner revealed she drinks pickle juice the night before the race and eats 2 tsp. of nut butter in the morning and a hard-boiled egg. Bacon and Ultima electrolyte hydration powder are carried during the race.

Others find they don’t need to fuel during their runs, while others just stick to water and electrolytes. Many report not feeling foggy or crashing, even when running 18 miles and training for Ultras.

“I realized that you can run a half-marathon just by fueling with water and electrolytes instead of sugary gels” runner Gulsum Ozturk Rustemoglu said. “No need to pack a gazillion items.”

Is The Keto Diet Safe For Training?

But is burning fat and not using carbs for fuel a good idea—let alone safe—for runners training?

Gorham said that while it’s not harmful to train for a race when following the keto diet, it might not be the best idea for endurance athletes looking to improve their performance. While the person is burning fat, they are also breaking down muscle mass.

Photo credit: Jenny Hill | Unsplah

“Some endurance athletes think that following a ketogenic diet will allow them to perform stronger and for longer periods of time by using fat as their main source of energy. However, no study has shown ketogenic diets to improve athletic performance,” Gorham said. “Studies have shown that following a keto diet can actually hinder athletic performance and athletes who use carbohydrates for fuel are more likely to improve their performance.”

According to Gorham, many keto dieters experience constipation caused from staying away from high fiber foods like fruits, vegetables, and whole grains.

And without carbs, some runners find themselves run down and lacking energy when training back-to-back days.

“As someone enters into ketosis they typically feel tired, weak, and even nauseous,” said Gorham.

And since some carbs are allowed, some runners do consume carb loaded gels during those long runs—many even able to stay in ketosis.

“Distance runners, in particular, need carbohydrates on long runs to prevent hitting a wall and feeling a crash in their energy,” she said. “While distance runners do pull from fat stores on long runs, by replenishing carbohydrates with gels, sports drinks, or snacks on their runs they will boost their energy and improve their performance.”

Benefits of Running Keto

That’s not to say that no runner should go keto. In fact, there is a study that did find a benefit. After following the diet for 10-weeks, five endurance athletes had an improvement in their body composition. However, not in their performance.

For runner Heather Ziegler, she has not “hit the wall” during her long runs as a keto dieter. In fact, she feels better during miles 3 to 10 compared to when she was a carb runner. “As a carb runner I would need to re-carb after a long run and would be exhausted, “ she said. “As a keto runner sometimes I’m not even hungry after a long run and still have energy throughout the rest of my day.”

Photo credit: David Marcugb

Its’ the runners who run very long distances (think ultra runners who run 30 plus miles while training) who see the best results. That’s because the body starts to use stored fat during those later miles, so being fat adapted is the way to go.

“For me, the biggest advantage has been not feeling ravenously hungry afterward,” keto runner Kelli Neier said, “and also not feeling muscle soreness the next day.”

Some runners are able to run longer and with less recovery time between long runs. “I like the fact that I recover so much quicker,” Keith Kettery said while revealing he ran 42 miles on the weekend, then is back to running on Tuesday.

Others reveal being able to run faster and are lighter on their feet since losing weight on the diet.

It might not be for every runner, but those looking to try to diet while training should know to be patient and give the body time to adapt. It could take weeks before runs don’t feel so awful and hard. Most importantly, don’t forget electrolytes before, during and after.


  1. HEATHER MAYER IRVINE, What Is the Keto Diet and Should You Try it?, Running Website
  2. ruled.me, What is a Keto Diet?, Keto Website
  3. Jenna Gorham, The truth behind the 'keto' diet, Blog
  4. Reddit, keto FAQ, Forum
  5. Thrive/Strive, 17 Keto Recipes That’ll Make You Forget You’re On a Diet, Nutrition Website
  6. Caryn Zinn, Matthew Wood, Mikki Williden, Simon Chatterton and Ed Maunder, Ketogenic diet benefits body composition and well-being but not performance in a pilot case study of New Zealand endurance athletes, Journal website

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