If you took a class on nutrition, the very first thing you would learn is that there are three sources of calories: carbohydrates, fat, and protein.
As all runners know, carbohydrates are the primary fuel if you want to run fast. But there’s a problem with carbohydrates—your body just can’t store that many.
That’s why hitting the wall, or “bonking,” is such an issue in the marathon.
Once you run out of carbohydrates, your ability to produce energy drops dramatically and you have to slow down.
But, there’s a fourth source of energy that might offer a way out of this conundrum, and that is ketones.
You’ve probably heard of ketones thanks to the ketogenic diet, which claim to leverage the benefits of ketones, in exchange for a diet that’s almost entirely fat.
In this article, we’re not going to look at the ketogenic diet, but rather explore whether ketones can help you run faster?
Let’s start with understanding what ketones are, then move into the research on whether they can actually improve endurance performance, move into any drawbacks, and finally recommendations for how to best implement in your training.
What Are Ketones?
Ketones are molecules produced when your body metabolizes fat, but they don’t come up much in traditional nutrition because when you are well-fed on a balanced diet, your body does not rely heavily on ketones for energy.
However, ketones play a big role in two situations: fasting and carbohydrate-restricted diets.
If you are fasting, or if you adopt a diet that’s extremely low in carbohydrates, something interesting happens in your blood after about four days: the concentration of ketones increases markedly, which is a sign your body has transitioned to ketosis.
In this state, your body is more readily able to burn ketones for energy during exercise. Burning ketones means your body uses less carbohydrates and produces less lactate, which could theoretically lead to better performance.
Some ultramarathoners have adopted ketogenic diets to shift their body’s fuel sources to rely more heavily on ketones, with the hopes of being able to run further and faster by relying on fat and ketones as a primary energy source.
However, sticking to a ketogenic diet is extremely difficult, and research has found that the lack of carbohydrates can be a real impediment to performance.
According to a 2015 scientific article by Louise Burke at the Australian Institute for Sport, low-carbohydrate diets have repeatedly been shown to impair high-intensity endurance performance because your body down-regulates its use of carbohydrates during exercise.
But what if there was a way to leverage the benefits of ketones without actually being on a ketogenic diet?
Could an Exogenous Ketone Supplement Help You Run Faster?
Cutting-edge exercise physiology research has suggested that taking “exogenous ketones” as a supplement might allow your body to lean more heavily on ketones during exercise, without having to restrict your carbohydrate intake.
An influential study published in 2016 in the journal Cell Metabolism made this claim, bolstered by both cellular metabolism data and real time trial performance from elite cyclists.
The paper, published by a team of researchers at Oxford, showed that a ketone supplement boosted levels of ketones in the blood, just like going on a ketogenic diet.
Moreover, taking a ketone supplement decreased blood lactate levels and increased performance on a cycling time trial, even when consumed alongside a traditional, sugar-rich sports drink.
These results created quite a stir in the exercise physiology community and kicked off a lot of new studies and reexamination of older studies on the potential performance enhancing benefits of exogenous ketones.
Let’s take a look at some of the research.
Improved Mitochondrial Efficiency
An influential paper published in 2015 formed a lot of the backbone about the potential energy-enhancing benefits of ketones, specifically ATP.
The study demonstrated that ketone oxidation results in remarkably efficient ATP production – as much as 28%. This means your working muscles are able to contract more powerfully with lower oxygen consumption.
Moreover, this study also showed that burning ketones for energy generates less oxidative stress, which can damage many cellular organelles.
The downside of this study is that it was conducted on rats and not humans exercising. The gold standard is always actual endurance athletes being tested.
Luckily, the promising results of this paper did lead to more research. Specifically, a 2021 study that also looked at mitochondrial efficiency and exogenous ketones.
In this study, endurance-trained athletes performed 60 minutes of incremental cycling exercise at the intensity of 25%, 50% and 75% of their VO2max. Compared to the control condition, ingestion of exogenous ketones improved mitochondrial efficiency by 7%, enabling the athletes to do more work with less oxygen.
Glycogen Sparing
The other main potential benefit of ketones is less reliance on glycogen as a primary fuel source.
This potential benefit was solidified in a 2016 study, where endurance-trained athletes cycled for 2 hours at 70% VO2max intensity on two occasions – after drinking only a carbohydrate solution or after consuming carbohydrates with an exogenous ketone product called deltaG.
Muscle biopsies were performed after the 2 hours of exercise to examine muscle glycogen levels. Significantly more glycogen was preserved after drinking the deltaG and carbohydrate mixture.
Such results suggest that raising your blood ketones delays glycogen use in the initial stages of endurance activity. As a result, more glycogen is available towards the end of the race, which can prevent you from hitting the wall.
Overall Performance
Another interesting benefit of exogenous ketones emerged as researchers delved into the topic – direct improvements to overall performance.
The same 2016 study on glycogen also had cyclists train for one hour at 75% Wmax, followed by a 30-minute time trial. They performed the exercise on two separate occasions, once with a carbohydrate drink only and then with a deltaG and carbohydrate drink.
On average, athletes cycled 411 meters further after drinking deltaG, which translates into a 2% performance improvement.
Workout Recovery
Some of the more interesting research since 2016 has been on the recovery aspects of ketone supplementation.
A paper published in Frontiers in Physiology demonstrated that supplementing with ketone esters during recovery increases the activity of mTORC1, a cellular signaling pathway that’s intimately involved with muscular growth and recovery.
These findings suggest that ketone supplementation could be a useful recovery strategy, particularly after long, tough training sessions that damage your muscle fibers, like a hill workout.
Even better, the use of exogenous ketones has been shown to help improve recovery and extend performance during intense training blocks.
In 2019 a group of researchers aimed to investigate if deltaG, a leading ketone supplement, could prevent a decline in performance induced by overreaching.
The recruited athletes were pushed to their limits. They trained 2 times a day, 6 days a week for 3 weeks, and the total training load increased every week. Participants in the experimental group received deltaG and a standard carbohydrate+protein shake after each training session and 30 minutes before sleep. Those in the control group received only the carbohydrate+protein shakes.
The workload in these sessions did not differ between groups in the first two weeks, but those who drank deltaG showed a 15% greater training load in the third week. Moreover, those in the deltaG group showed 15% higher power output during the 30-minute time trial to end the study.
Recommendations
Training and racing using ketones as fuel was once something that seemed to hold tremendous promise, but the practical limitations of being in a ketogenic state, especially for runners, prevented it from being a truly beneficial way to improve performance.
With the advent of exogenous ketones, regular runners are now able to take advantage of the clear performance-enhancing benefits without the downsides.
While the most obvious benefits of ketone supplementation (less glycogen usage and less lactate accumulation) are most relevant to marathoning and ultramarathoning, some research has found that ketone supplements could even improve performance in events as short as the 800 meters.
What kind of Ketones to take?
The research has shown that ketone esters are superior to ketone salts due to their ability to raise the concentration of beta-hydroxybutyrate (BHB) levels to the 2mM range.
Most studies that used ketone salts where only able to raise BHB levels to 0.8mM whereas esters were shown to raise levels to 1.6mM.
Targeting the 2mM BHB range puts your ketone levels at about equivalent to 2 days of fasting.
This is why my recommendation if you’re going to use ketones is deltaG.
Not only are deltaG ketone esters, but the product was developed in collaboration with researchers at NIH and the University of Oxford. They are at the forefront of ketone science.
As a note, we have partnered with deltaG in the past because we strongly believe in their product. But, that did not influence the research we did for this article.
How to take Ketones
In terms direct performance advantages, experiments thus far usually involve taking ketones about half an hour before exercise, alongside water or a standard sports drink.
For those racing marathons and half marathons, the research does support including them in your intra-race drink of choice to aid in glycogen sparing.
Research also shows taking ketones directly after exercise can aid in recovery, especially during periods of intense training. Therefore, they would be recommended during the “meat” of your race specific training cycle.
In short, you can really take them anytime you want to align with your desired performance or recovery outcome.
Want More?
We conducted an in-depth interview with Brian McMahon, runner and Chief Strategy Officer at deltaG – a company that makes exogenous ketones
He talks about what ketones are, the difference between options out there on the market for runners (particularly, the difference between ketone “esters” and “salts”), their benefits for running performance, recovery, and even day to day life, recommended programs for usage, and much more.
In addition to the science of ketones, Brian and I do a deep dive into the history of its development and usage in military and endurance sports environments, and talk a bit as well about what the next few years could look like for its adoption in the running community.
