Many runners are curious about the ketogenic diet because the promises are alluring. But does keto and running work together? What are the drawbacks?
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.
Is There Evidence that Keto and Running Mix?
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
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!
- 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!