Keto and Running: Is the Low-Carb Ketogenic Diet for Runners?

Many runners are curious about the ketogenic diet because the promises are alluring. But does keto and running work together? What are the drawbacks?

ketogenic diet for runners

Before anybody decides to jump on the keto bandwagon and abandon carbohydrates, they should seriously consider whether this diet is right for them.

Because while most folks are aware of the benefits, few fully understand the drawbacks. And most importantly, the sacrifices that are needed to adhere to such a restrictive diet.

After all, the Ketogenic Diet meets Matt Fitzgerald‘s definition of a ‘diet cult:’

A diet cult is any diet that is based on the false idea that there’s a single ideal diet for humans. The underlying essence is that false belief that this diet is better than any other or even the only right way for anyone to eat.

As the world’s most prolific omnivores, humans are uniquely evolved to eat a wide variety of foods – and thrive. There’s virtually no reason to abandon such a powerful adaptation.

To determine if keto and running are a match made in heaven, we have to answer some questions:

  • What does it take to truly adhere to the ketogenic diet?
  • Are there drawbacks to removing almost all carbohydrate from your diet?
  • How sustainable is the diet in the long-term?
  • Can some elements of keto be used without strictly adhering to the diet?

First, let’s get a good working definition of the ketogenic diet.

What is the Ketogenic Diet?

At its simplest, Keto is a high-fat, adequate protein, and extremely low-carbohydrate diet. It’s similar to the Atkin’s Diet and other low-carb diets with the exception that you need to be in ketosis to properly adhere to the diet.

Wikipedia has a great explanation of how this works:

The diet forces the body to burn fats rather than carbohydrates. Normally, the carbohydrates contained in food are converted into glucose, which is then transported around the body and is particularly important in fueling brain function.

However, if little carbohydrate remains in the diet, the liver converts fat into fatty acids and ketone bodies. The ketone bodies pass into the brain and replace glucose as an energy source.

The production of ketones signifies that an individual is in ketosis. And to remain in ketosis, carbohydrate intake needs to be less than 50g per day. That means most runners favorite foods are mostly off limits, like:

  • Fruit (!)
  • Legumes / lentils / beans
  • Bread and other whole-grain foods
  • Starchy vegetables like sweet potatoes and beets
  • Alcohol 🙁
  • Many sauces and marinades that are high in sugar

As you can see, your diet will most likely need a complete overhaul if you decide that keto is for you.

And there are certainly drawbacks. Potential side effects may include constipation, high cholesterol, acidosis, or kidney stones.

Fore more drawbacks (and benefits), check out UPG’s Keto Benefits and Side Effects resource.

Is There Evidence that Keto and Running Mix?

Carb Heavy Diet

Some runners have seen tremendous success with the ketogenic diet. But we shouldn’t rely on outliers…

Zach Bitter is a famous case study of a runner who eats keto. But there are some caveats:

  • He’s been doing it since 2011 (it takes a long time to become fat-adapted)
  • His diet is not strictly keto (he cycles between ketosis and simply low-carb)
  • As a pro runner, he has enough time for the Ketogenic Diet (it’s more of a hassle)
  • He focuses on ultramarathons (fat as fuel makes more sense the longer the race)

These are very important considerations! Because if you don’t have the time, patience, and discipline for the Ketogenic Diet, then you won’t get any of the benefits.

Moreover, any runner training for “normal distances” (say, the marathon or any shorter race) is going to want access to carbohydrates for fuel. They’re limited but they’re more powerful for faster racing. This is addressed in more detail in this conversation with a dietitian.

The higher intensity the race, the more you’ll need carbs (rocket fuel) rather than fat (solar energy).

What About Low-Carb Tour de France Cyclists?

There’s been a lot of focus on the last few years of the Tour de France because some cyclists have reportedly been eating a Ketogenic Diet.

For a race that lasts thousands of miles over weeks, it’s also an event that lends itself to fat-adapted athletes. Most mortals are not cycling 100+ miles every day for the better part of a month…

But even so, these cyclists are not actually eating a strict Keto diet. They’re periodizing their diets to strategically get some of the benefits of eating low-carb without the problem of not having enough fuel for higher-intensity cycling.

Ketone supplementation is also happening, but this is being done without adhering to the Keto diet.

Clearly, it’s important to understand the nuances of elite athletes’ diets and refrain from copying them exactly.

But it’s apparent that some aspect of periodized nutrition or carb cycling can be helpful. But which tweaks will help your performances?

Keto Tweaks That Might Work

keto and running

As long as you never need a big burst of energy, you’ll thrive eating keto. But bursts of energy are what we do as runners!

Just think…

  • Anaerobic workouts require high-intensity running
  • Races at the marathon distance or shorter require bursts of energy
  • Mid-race surges are, by definition, bursts of energy

If you’re relying on the Ketogenic Diet, your performances will suffer if you’re trying to run fast.

But there are some elements of the diet that could help runners:

  • Running morning runs on an empty stomach to improve fat burning capabilities
  • Cycling through low- and high-carb weeks depending on the training
  • Supplementing with exogenous ketones (this is a good option)

Ultimately, only highly dedicated runners training for ultramarathons ought to be thinking about the Keto Diet.

Other runners will have trouble sticking with the diet, the adaptation timeframe will hamper weeks of training, and the intensity of shorter races means that carbs are necessary to reach your potential.

Instead, a diet optimized for running has the potential to boost your recovery and performances.

How to Eat for Endurance the Right Way

The vast majority of runners will thrive with the body’s preferred fuel source for high-intensity exercise: carbohydrates.

But don’t take my word for it. I’ve talked to some of the brightest Registered Dietitians about optimal fueling for runners, like:

  • Nancy Clark, arguably the most famous RD in the world, and author of The Sports Nutrition Guidebook
  • Annyck Besso, RD
  • Anne Mauney MPH, RD (my partner on our Nutrition for Runners program)
  • Lauren Kort MS, RD (a national award winner)
  • Kristina LaRue, RD, CSSD, LDN
  • Lauren Trocchio, RD, CSSD, CSOWM, LD
  • Heather Caplan, RD
  • Lindsey McCoy, RD, CSSD, LD

These nutrition experts:

  • Have advanced degrees and certifications in nutrition
  • Advise Olympians at the world-class level
  • Appear on television as thought leaders in the diet space
  • Consult with pro sports teams like the Boston Red Sox and Orlando Magic

I’ve always said that if you’re going to model your behavior after someone, model it after the best. None of them believe that keto and running are a practical combination.

They all recommend a balanced diet, rather than a diet that ignores an entire macronutrient. That’s because a well-rounded diet works best for endurance runners!

To help you optimize your diet for running, sign up here and I’ll send you two bonus podcast episodes with Anne Mauney, RD on fueling and nutrition Q&A. We dive deep into your nutrition questions so you can focus on training.

I’ll also send you our Registered Dietitian-approved shopping list to make picking out healthy foods at the grocery store even easier!

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  1. Mind you that a keto diet doesn’t “abandon carbohydrates”. It just states you don’t need as much as you think.

    • Let’s not split hairs. When you’re required to eat <10% of your calories from carbs, that's virtually abandoning them.

      • Leonardo Garcia says:

        …especially considering that the fastest runners consume diets anywhere from 60-80% from carbohydrate.

        • Exactly. Learning from the best should always be a priority!

          • Just curios as to whether you’ve read Alex Hutchinson’s Endure? Besides being a wonderful read for all endurance junkies, there is a chapter detailing repeated studies done comparing ketogenic diet in performance of olympic race walking (where you do not seem to need the anaerobic upper edge that ketogenic diets squelch) and besides repeated failure to match performance on a high carbohydrate diet, those eating the ketogenic diet became less efficient in their energy use (i.e. keto athletes required more oxygen to produce energy) and crippled their abilities to use carbohydrate for energy. Basically, the keto athletes locked themselves into using fat for energy producing substandard performance and substandard physiology.

            Also, one bit of nutritional science that I recently discovered as I went down a research rabbit hole was that the consumption of refined oils and high fatty foods (eggs, dairy, meat, and to some extent, nuts) impairs arterial function. Not an ideal scenario for health and for any type of athletic endeavor.

  2. Great article. I could not survive long on the keto diet. I is good to hear some level headed information for runners. You took all types of training into consideration in a thoughtful way.

    I would like to hear your thoughts on pre race 2 day carb depletion. Followed by carb loading?

  3. Dolores Peralta says:

    I’ve used the keto diet to help me lose weight but as I’ve become more serious about my running, I’ve found that it just doesn’t provide the energy I need to sustain my runs, both long and short.

  4. Leonardo Garcia says:

    I’d urge anyone considering following a diet as unhealthful as a true ketogenic diet to watch Dr. Michael Greger’s recent series on explaining what current scientific research has shown. The health repercussions and compromise do not outweigh the short term “benefits” that most attribute to the diet. If you are severely epileptic, it may be your only choice. Otherwise, a whole food plant based diet (fruits, vegetables, whole grains, starches, nuts and seeds) is the way to go if you are after health. The registered dietitians mentioned above have one thing in common, the curriculum they study and advocate is underwritten by the meat and dairy industry. I would not take my advice from them for health, sports performance, or disease prevention and reversal.

  5. What’s the point of ketone supplementation? Is there any evidence that it does anything? Keto dieting is a non-starter for me, but if there’s some evidence-backed way that supplementation helps, that might be worth checking out. I’m just skeptical because there are so many supplements out there and basically the only ones that do what it says on the label are creatine and protein.

  6. Jason, thank you for the post! I’ve done many dietary experiments over the years with macro manipulation all over the map. I did Keto for 6 months while training for an Ironman triathlon. It helped with all my longer training days but higher intensity training did suffer. I learned a lot which was the biggest take away. What I do now is close to the “40/30/30”diet (fats, protein and carbs). (Closer to 55/25/20). I’ve found this mix to work very well for marathon training (for yours truly). In my humble opinion with all the diets we can choose from, all we are looking for is to be healthier: which is great! But it requires a n=1 study, bc we are all unique. (This takes time). A “balanced” diet really means finding your specific goldilocks mix.


  7. Both my wife and I have tried the ketogenic diet and we responded very differently. I was able to go into ketosis (verified via urine ketone measurements) within 72 hours. But, even after two weeks my wife never measured elevated ketones. I’ve found that I do best with a low carb but not truly ketogenic diet. I’ve adopted a routine where I skip breakfast and have a modest lunch and rather full dinner. That is nearly completely opposite of the information I learned growing up! However, I recently ran a PR in a half marathon. All I had for breakfast was half an avocado and I small serving of exogenous ketones that I dissolved in a waist belt water bottle. One data point is not enough to draw any conclusions. However, I think the evidence is growing that genetic factors and perhaps variations in our gut microbiome are highly influential in how we respond to dietary interventions. This notion that one size fits all diet will work is a thing of the past. I recommend friends and family try to balance their diet and self-experiment to find what works for them.