A Nutritionist Explains the Science Behind Ketones for Runners

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First developed by the U.S. military, ketone supplements have caught on among runners and other endurance athletes. The promises are lofty: Pound back some ketones, and you’ll boost endurance by modifying energetics, avoid energy crashes, recover better, and experience a profound mental boost. Even pro athletes have become more public about their use of ketone drinks.

Historically, people increased the amount of ketones circulating through their bodies by following a low-carb eating plan such as the keto diet. The theory was that ramping up ketone production and being in a state of ketosis would turn you into a fat-burning machine, allowing you to run to the moon without hitting the wall. Sadly the theory failed to pan out, as the benefits of low-carb eating for endurance athletes have largely been shot down. However, a handful of companies including Kenetik and Ketone-IQ now produce ketone supplements that let athletes fuel on these compounds while still keeping their morning toast.

But do they deliver on their promises? Let’s explore the science behind ketones for runners, including their potential benefits, drawbacks, and whether they’re the game-changer that’s worth a (hefty) chunk of your hard-earned cash.

What Are Ketones?

In layman’s terms, ketones are endogenously produced molecules created when the liver breaks down fatty acids instead of glucose as a fuel source. It happens when the body is deprived of carbohydrates and glycogen stores are depleted, and instead must burn off a lot more fat as a fuel source for the brain, skeletal muscle, and other important organs.

Ketones can cross the blood-brain barrier, allowing them to fuel both the brain and the body. This state of ketosis can occur during starvation (energy deficiency) or resulting from a self-imposed exodus of carbs from the diet, as is the case with the keto diet. “Our bodies also create endogenous ketones in the liver during periods of energy deficiency such as during long runs and prolonged endurance training,” adds running coach and exercise physiologist Laura Norris.

What’s So Great About Ketone Supplements?

Exogenous ketones (orally consumed ketones) are promoted as a way to help us achieve a state of ketosis without dietary modifications. Chug back a ketone-laced drink and you can ramp up the ketones in your body without the hell of needing to give up bread and pasta.

“Research demonstrates that ketone supplementation can elevate blood ketone levels similar to that of which one would experience in a state of nutrition ketosis—without the extreme dietary intervention,” Norris says. This means that ketone supplements provide a “loophole” for athletes who typically would not be eating a carb-stingy diet.

Before we look at whether the research supports the benefits of exogenous ketones for running, it’s helpful to understand the mechanisms of why people think they are, quite literally, awesome sauce.

“Theoretically, if your body uses exogenous ketones for some energy production during endurance sports, you then spare glycogen stores,” explains Norris, which reduces your body’s usual need for efficient-burning carbohydrates. “And making your glycogen stores last longer may be the key to avoiding hitting the dreaded wall during long races and training sessions.”

So on paper, it seems like a no-brainer: Taking in exogenous ketones during a run should help you go longer as it allows your muscles to access an additional source of fuel when you are moving along. In essence, they are the third fuel tank after carbs and fat. The net benefit is that you are able to better preserve your precious carb stores during long efforts for times when you need them most—such as high-intensity efforts—says one study in Cell Metabolism.

Many runners simply add ketones on top of their normal high-carb fueling strategy as an extra layer of protection against the bonk. You consume ketones, levels go up quickly and then come back down over several hours, as your body uses up the ketones as fuel. Think of it this way: Your body would be able to better switch between fats and carbs as its energy source the same way as a hybrid car engine can flip-flop between gas and electricity.

This glycogen-sparing metabolic switch is also believed by some to lower oxidative stress in the body, increase mitochondrial efficiency that lets people to do more work with less oxygen, improve mental alertness during long duration workouts due to their effect on dopamine production, and decrease lactate production which would cut down on the acid build-up in your muscles during a run making a workout seem easier.

So Are Ketones for Running Actually a No-Brainer? 

The first notable study of ketone ester supplementation in athletes was published in 2016; this study set the tone for the conversation about ketones, finding that eight well-trained cyclists went 2 percent further (one quarter-mile farther) in a 30-minute time trial after taking ketone ester mixed with carbohydrate before the test. But despite the buzz the preliminary research generated, the majority of science on exogenous ketone use for runners suggests that ketones aren’t the rocket fuel we want it to be and leaves many questions unanswered.

For instance, a 2019 study in Medicine and Science in Sports found that ketone supplementation did not improve 10K running performance in trained runners. Similarly, another 2020 study found no differences in 5K performance when runners supplemented with ketones 60 minutes prior.

And there is some expert consensus outside of studies as well: “Most evidence indicates that ketones have no direct impact on performance,” says Chiel Poffé, PhD, a prominent Belgium-based ketone researcher. Worse yet, he says that exogenous ketones may even hamper performances in workouts lasting 20 to 60 minutes in duration. “The specific reason remains unknown but is most likely due to the induced acidosis and reduction in blood buffering capacity with ketone use and also potential changes in metabolism.”

All this is to say that we should temper our expectations for exogenous ketones. Most of the pro-ketone chatter out there is based on subjective feedback, not objective data, and it’s possible that the placebo effect accounts for much of the perceived benefits.

But Can Ketones Really Make You a Better Runner?

To date, there is currently little to no evidence on whether ketones can improve marathon or ultramarathon performance, says another study from the Journal of the International Society of Sports Nutrition. “It is very difficult to measure the impact of a singular supplement in ultra-marathon events since there are so many confounding variables,” Norris adds.

Adding to that, there’s very little research surrounding ketones’ effects on women. “Research is also lacking on how ketones could impact female athletes who already have higher fat oxidation rates or untrained athletes who may not have the metabolic flexibility during exercise compared to trained athletes,” Norris notes.

It also may just be a matter of what you take your ketones with. One recent study showed a five percent increase in power production after three hours of exercise with the co-consumption of exogenous ketones and sodium bicarbonate (another “hot” endurance supplement that’s used to buffer acid build-up in muscles during exercise).

Researchers theorize that this may result from sodium bicarbonate counteracting the acidosis produced by ketone consumption. So bicarbonate may be a way to unlock the effect of ketones on performance—that is if you can wrap your head around the idea of taking both of these expensive and newly researched supplements during runs.

Do Ketone Supplements Improve Recovery?

If not during a run, then are ketones best used for post-run recovery? There is growing enthusiasm that ketones might be more helpful for recovery from intense workouts or during periods of frequent training.

Research hailing from Dr. Poffé’s lab found that trained male athletes who took post-exercise ketones showed fewer signs of overreaching during an intensive training block (two training sessions per day, for six days a week, for three weeks). He has also found post-exercise ketones to be helpful in stimulating muscular angiogenesis, which is fancy speak for muscle-building, as well as sleep efficiency after a bout of gung-ho exercise.

“It appears that the benefits of ketones in recovery are not due to their role as an energy substrate but as a ‘signaling molecule,’” Poffé says. “Meaning that they can change specific proteins and metabolites such as dopamine.”

So, Should You Take Ketones for Running? 

While there are still a lot of open questions about the usefulness of exogenous ketones in sport, and I can see how they would appeal to runners seeking any sort of an edge, the non-anecdotal evidence doesn’t strongly support their use for improving performance, aside from marginal recovery gains. And so far the sales pitch for exogenous ketones has outpaced the science.

“The science is not convincing enough for me to recommend ketones as an ergogenic aid, particularly when more efficacious supplements such as intra-exercise carbohydrates, caffeine, and sodium bicarbonate exist,” Norris says. “However, if a runner is very curious about ketones, has the budget for them, and handles a high training load (over 9 hours training per week), then they may opt to try them.” Norris is also a little more bullish on ketones for top-level athletes who could potentially see benefits from using the supplement as a post-workout supplement during overloaded training blocks.

The Long-Term Effects of Ketones for Runners (and Other Cautions)

It’s also worth noting that we don’t have any long-term data on the health impacts of ketone supplements. What happens if you suck back ketone drinks on the daily? “We do not fully understand any metabolic impacts of long-term ketone supplementation,” Norris cautions.

Ultimately, you have to weigh the drawbacks with the potential benefits of ketones when deciding if you should use them as a supplement. Beyond the potential for GI revolt and potential placebo effect, ketone supplements have two notable drawbacks: They are pricey, and they generally taste very bad. (Though a few brands are working on taste improvements, mainly using added sweeteners and added flavors.) For example, a six-pack of Kinetik will set you back $25, while 24 shots of Ketone-IQ ring in at more than $100.

Like any supplement, it’s also important to note where the ingredients come from. Norris suggests picking a ketone supplement with third-party testing. “Third-party testing means that an organization outside of the brand has tested the supplement for purity, efficacy, and safety.” Norris says you can look for the NSF or Informed Sport labels to know that a ketone supplement is third-party tested and contains what it says it does.

But even if you can effectively guarantee purity, be realistic about the science on what ketones can (and cannot) do for you.