In pursuit of better performance, we do a lot of crazy things. Taking exogenous ketones seems to be getting more common, but is it still crazy? Find out.
Should You Take Ketones for Cycling?
The State of the Science in 2020
I first discovered exogenous ketones the hard way. By tasting them. I had heard about this mythical performance supplement from friends who had the “inside line” on what the pros were eating and drinking. “Ketones!” They said. Everyone’s into ketones now. So, I tasted them. I no longer use ketones.
That’s not a statement on their science and speed boosting ability, just on their flavor. They taste terrible. But is that bad taste worth it? Do they help enough to make up for the nose-twisting disgust they engender in most people? To me, no. But I’ll let the science speak so you can make your own decision. Besides, companies are making them tastier all the time, and the way they’re flying off shelves means someone finds them valuable.
What and Why
The ketones I’ll be discussing are exogenous ketones, most often referred to as ketone esters or ketone salts (KE or KS, they’re different things, but I’m going to talk like they’re the same, for simplicity’s sake). I’m not talking about a ketogenic diet. That’s a much more complex topic that we don’t have room or time for today. Instead, I’m talking about the ketones you can buy in a little bottle, squeeze into your coffee, and chug before a ride. These are lab-crafted supplements that promise to improve your cycling ability and recovery. We’ll find out if they do soon.
Ketone usage and metabolism have clear physiological bases. They’re commonly used in our bodies day to day. Ketone bodies are leftover bits of fatty acids that can be used for energy by the majority of our cells. Normal humans use them for energy all the time, especially when waking in the morning, before eating breakfast. They’re “bridge calories” that help get us to the next meal without overtaxing our energy stores. Faster to use than new fatty acids and more preservable than glucose, ketone bodies are great fuel for our fasted selves. As cyclists, we use ketones often. On long rides, especially low-effort, endurance work, ketones are used to keep us going as we break down fatty acids and seek to spare glucose and glycogen when it’s not required. But these are all endogenous ketones: ketone bodies produced from the breakdown of fatty acids inside our bodies. We’re going to talk about exogenous ketones. Those from outside your body.
Produced by a few different companies in a few different packages, exogenous ketones are all essentially the same. They’re a mixture of naturally produced ketones that have been chemically processed into a more stable, usable product. Just a chain of carbon molecules with a couple of specially placed oxygens that our bodies can break down into energy. The metabolism of exogenous ketones is pretty much identical to that of endogenous ones. They’re broken down and used for energy in the same way. The main difference is the quantity. Supplementation with exogenous ketones can push blood levels to about 5mmol/L, septupling the standard fasted human state of about 0.7mmol/L. If you’re already using fasted rides to improve your body’s ability to use fat as fuel, exogenous ketones increase the availability of ketones compared to fasting.
Now we have what they are, what our bodies use them for, and what exogenous ones do. But it still begs the question, why are they good? Why use last-resort fuel to energize our bodies? There are two main answers: efficiency and signaling.
The Efficient Ketone
Aerobic energy production from any nutritional source relies on the electron transport chain (ETC) located in mitochondria. Glucose from carbohydrates and ketone bodies (both exogenous and from fat) are broken down into small pieces, then fed through the ETC to generate large amounts of ATP, the molecule that cells break down for energy. Due to differences in their molecular structures, ketones are significantly more efficient than carbohydrates on a per carbon basis (31% to be exact). For every unit of ketone your body pushes into the ETC, it gains 31% more energy than it would with a unit of carbohydrate. This is a massive difference with significant metabolic effects.
Since endurance performance is essentially the product of three variables, VO2max, lactate threshold, and efficiency, increasing efficiency can increase power output at an identical VO2 level. At the same time, increasing efficiency can also lower the VO2 required to meet the same power level. You’ll breathe less hard to hit the same power number. Ketones won’t make you 31% better, but they could allow significant gains. This necessarily leads to another question: why don’t we use ketones for fuel all the time?
There are two answers for this, speed and storage. The freeing of ketone bodies from body fat requires much more time than the freeing of glycogen from the liver and muscles. That’s why glycogen is most commonly used with high-intensity exercise, while ketones are used more often with long, endurance work. Indeed, ketone supplementation has been shown to slow down cyclists competing in 10km time trials, likely because the distance is too short for these athletes to use the fuel effectively.
The other reason they’re not used at all times is storage. Glycogen can only be stored for limited amounts of time, while fat can be stored essentially forever. Because of this, the body prefers to use up short-term fuel supplies first, before delving into long-term storage and potentially jeopardizing it.
This efficiency bonus is only noticeable in long efforts at low percentages of VO2max, once crossing 75% of VO2max, it appears that ketone supplementation can lower performance metrics. But that doesn’t mean they’re not valuable. Ketone bodies can help spare carbohydrate consumption and save glycogen for later, higher intensity efforts. In races that are largely flat and boring for the first few hours, but intense for the last bit, ketone supplementation could have significant benefits by saving glycogen for when quick access to fuel is needed. Another area where ketones provide ergogenic gain is cell signaling. This contains perhaps their greatest potential.
What 5mmol/L of Ketones Can Do
Ketone bodies are more than a fuel, they’re also a messenger to our bodies. Much of what we eat functions as a messaging system, telling our bodies what nutrients are coming in and where to put them. Ketones are no different, but the content of their message is.
Taken at the right time, exogenous ketones can stimulate our bodies to ramp up the repair process, store fuel for the future, and increase protein synthesis. The ketone bodies provide signaling to this end, but they have to be supplemented with the correct recovery nutrition as well. In study subjects that ingested post-exercise ketones along with glucose recovery drinks, glycogen storage was increased by 50%, while those that ingested a combination drink of protein and carbohydrates increased protein synthesis markedly. Both of these conditions modified muscle architecture and assisted with recovery times. This data indicates that ketones are potent recovery modulators and hold great promise for increasing one’s ability to repeat workouts, day in and day out. It’s no wonder that many cycling teams are purchasing them in bulk and TheFeed has seen them massively increase in popularity in the last two years.
The Wrap on Ketones — Where We Are Today
The state of the science on ketones is in motion, but we do have good evidence for their effectiveness as ergogenic aids today. They’re most generally applicable for use immediately after workouts, accompanied by a recovery drink that contains high levels of carbohydrates and protein, to help rebuild glycogen stores and synthesize new muscle. Additionally, they can be carbohydrate sparing when taken before endurance exercise, allowing one to preserve glycogen stores for later, higher intensity portions of rides and races. That leads to some dosage guidelines.
For improved performance in cycling races of greater than 2 hours, especially those that begin easily and finish at a high level, exogenous ketone supplementation prior to exercise is beneficial. This allows glycogen to be saved for later portions of the race.
For cycling races that start hard or are of relatively short duration and high levels of VO2max, avoid exogenous ketone supplementation, as it could decrease performance.
For recovery purposes, taking ketones with carbohydrates after a hard session can improve recovery for a second session occurring the next day or two days hence.
Taking ketones with protein can increase protein synthesis, changing muscle architecture more rapidly than exercise alone.
That’s the wrap on ketones, and should give you a good idea of where we are now and how they can help your cycling. These are a hot area of research and investigation, and I know that many professional cycling teams are doing their own, proprietary work to learn more about them as well. As that information leaks out, I’ll update this article to keep it up to date. For now, they appear to be an exceptional ergogenic tool, especially for long races ending in a climb (like Stage 1 of the Tour of the Gila) and a great general recovery tool. Unfortunately, they are still very expensive, so they won’t join everyone’s feed bag yet.
I’d love to hear your questions and comments on this topic and will answer as many as I can. Use the form below to ask questions about anything related to the science of endurance exercise, I’m always looking for new topics to dive into.
Sources
- Vandoorne, T. et al. Intake of a Ketone Ester Drink during Recovery from Exercise Promotes mTORC1 Signaling but Not Glycogen Resynthesis in Human Muscle. Front Physiol 8, (2017).
2. Holdsworth, D. A. et al. A Ketone Ester Drink Increases Postexercise Muscle Glycogen Synthesis in Humans. Med Sci Sports Exerc 49, 1789–1795 (2017).
3. O’Malley, T., Myette-Cote, E., Durrer, C. & Little, J. P. Nutritional ketone salts increase fat oxidation but impair high-intensity exercise performance in healthy adult males. Appl Physiol Nutr Metab 42, 1031–1035 (2017).
4. Cox, P. J. et al. Nutritional Ketosis Alters Fuel Preference and Thereby Endurance Performance in Athletes. Cell Metab. 24, 256–268 (2016).
5. Sansone, M. et al. Effects of Ketone Bodies on Endurance Exercise. Current Sports Medicine Reports 17, 444–453 (2018).
Luke is a cycling coach and physiologist from Richmond, VA who rides and races bikes all over the country. He’s an expert on the body in motion and its response to exercise and loves to share his knowledge with others. Find him @LukeHollomon everywhere.
