You’ve definitely heard of the ketogenic diet — starving your body of carbs to force it to burn fat and produce the mind-clarifying, brain-healing compounds known as ketones. You may have even heard of people and athletes ingesting ketone salts or drinks to propel them into or keep them in a state of ketosis. And if you were paying close attention during the Tour de France this year, you may have spied Team Jumbo-Visma openly drinking ketones mid-race.
The funny thing is, these athletes are not on a ketogenic diet. They are not fat adapted.
“For the last three years or so, we’ve seen Tour athletes fueling with carbs and then supplementing with exogenous ketones to score a two to three percent boost in performance from dual-fueling,” says Matt Johnson, a former competitive cyclist and co-founder of The Feed, an online sports nutrition shop and leading supplier of exogenous ketones in the U.S. “June was insane with team’s placing $10,000 to $20,000 orders for ketone esters and rush shipping them to France. We could barely keep up with it.”
Elite athletes biohacking to score a tiny edge? Nothing new.
But this is: a study in the Journal of Physiology says everyday athletes who aren’t on a keto diet, who aren’t fat-adapted, may improve their recovery by a whopping 15 percent just from drinking exogenous ketones after intense training days. And the news is spreading.
“We have also had a huge spike in individual athletes ordering the product that seems to be only growing,” Johnson adds.
Now, will this approach work for you? Here’s everything you need to know.
First, a quick biology lesson slash crash course in the trendiest diet of the twenty-teens: in an ideal world, your body breaks down carbohydrates into glucose, which is then transported and used or stored as energy for your muscles, organs and, most importantly, your brain.
Your brain is at the top of the pecking order — it gobbles about 20 percent of your total energy expenditure, a lot for a single organ — and if it’s not fueled, everything else stops functioning. When you deprive your body of carbohydrates, your muscles can use fat for fuel, but your brain can’t. Instead, your body has a fail-safe to prevent total shutdown: the liver starts converting fat into a superfood designed to save your starving brain: ketones.
Even if your body can adapt to burning fat quickly to fuel long runs and rides, it would still prefer to burn carbs. Which is why the notion of pro athletes downing exogenous ketone drinks without having to give up carbs is completely bonkers.
Ketones are essentially a fourth macronutrient — your blood sugar is stable, your body is burning fat and your brain has entered an almost elevated state of functionality. In ketosis — the state you reach when adhering to a keto diet — your brain starts producing more mitochondria (the little powerhouses of energy in your body) and better regulating neurons. Staying in a state of ketosis has been shown to help clear the brain of proteins that can lead to and worsen Alzheimer’s disease, reduce seizures in about half of people with epilepsy and even extend the lifespan of mice.
In athletes, staying in ketosis via a ketogenic diet can increase fat utilization during exercise (great, considering your body can store way more fat for fuel than carbs), help reduce body fat and sometimes improve endurance time trials and sprint peak power.
The catch: it all rides on you steering clear of carbs — with no slip-ups. If you eat more than your allotted count — typically 50 grams, which is one cup of pasta or just two bananas — your body falls out of ketosis and you don’t get any of these benefits. And pretty much all nutritionists agree that even if your body can adapt to burning fat quickly to fuel long runs and rides, it would still prefer to burn carbs.
Which is why the notion of professional athletes downing exogenous ketone drinks without having to give up carbs is completely bonkers.
So what are exogenous ketones, exactly?
In the early 2000s, as part of a DARPA program to enhance U.S. soldier performance, Oxford professors Kieran Clarke and Richard Veech set out to distill the exact molecular structure of one of the ketones our body produces. The resulting ketone ester is a specific molecule, butanedial, that converts directly to beta hydroxybutyrate, the ketone our liver naturally produces in the ketogenic state, when you digest it, explains Geoffrey Woo, co-founder and CEO of HVMN.
HVMN is currently the only company to produce ketone esters, as they lease the patent to Clarke and Veech’s molecular structure.
Now, keto followers are probably familiar with other brands of keto drinks (usually based on MCT oil) and ketone salts. But esters are different than these aids. MCT oils don’t produce ketones; they help put your body in a state of ketosis so it can start producing its own — but since that requires carbohydrate starvation, that’s not an option for dual-fueling athletes, Johnson explains.
Ketone salts, meanwhile, use beta hydroxybutyrate as well, but by their nature, they’re bound to a mineral. “Because you have to take so much ketone to raise your blood levels enough to see an effect, you’re also gaining a lot of mineral load. This leads to a lot of GI issues in athletes,” explains Woo. That, plus the fact that the salts don’t raise your ketone levels that much, leaves a lot of room for a superior product. “There has been minimal testing on the aids but the HVMN esters have been tested and verified,” Johnson says.
“Ketone esters are a way to eat ketones directly that’s going to convert 100 percent to ketones in your body,” Woo adds.
Why athletes are fueling with both carbs and ketones
Woo says professional athletes drinking exogenous ketones during a race report about a two to three percent increase in performance. That matters in an event like the Tour — but the real benefit for athletes, especially everyone other than Egan Bernal or Geraint Thomas, seems to be in downing a bottle once the race is over.
The aforementioned Journal of Physiology study, conducted by seemingly impartial Belgian researchers, simulated a Tour with everyday athletes: 20 fit men trained twice a day (HIIT or intermittent endurance training in the morning, then 1.5- to 3-hour endurance sessions at night), six days a week for three weeks. Half drank a ketone ester after each workout while half drank a placebo.
After three weeks, the guys were shredded — everyone showed signs of cardiovascular, hormonal and perceptual overreaching. But those who had taken ketone esters regularly had significantly less damage in all these areas, and on a two-hour endurance test, they were able to ride at a higher sustainable pace and produce more power in the final 30 minutes compared to guys who recovered regularly. All in all, researchers estimated the ketone esters helped improve recovery by 15 percent.
Mainly, it’s providing your body with another option for fuel, says Jonathan Scott, Ph.D., R.D., an assistant professor at the Uniformed Services University in Bethesda, Maryland who researches performance nutrition and dietary supplements.
“You can still have your cake and eat it too. Athletes don’t need to consume a diet that’s extremely restrictive, and they can then consume exogenous ketones to introduce yet another fuel source the body can use.”
Your brain is either going to use glycogen or ketones for power. If ketones are available, glycogen is spared and your muscles can instead use that energy to fuel fiber repair and metabolic cleanup. What’s more, now your body isn’t going to break down other structures like muscle fiber to get your brain the fuel, saving your body extra damage.
And, because ketones keep your blood glucose stable, your body is steadily producing insulin, which sweeps glucose into your cells, continuously topping off the pool of energy as it’s being used and at a much faster rate than you’re able to with food, Scott explains.
In addition to faster post-exercise glycogen replenishment, a 2018 Italian study in Current Sports Medicine Report found that exogenous ketones decrease proteolysis (the breakdown of proteins into amino acids) and act as metabolic modulators and signaling metabolites.
There’s also some chemistry research to suggest exogenous ketones may help realign your hormone production, adds Krista Austin, Ph.D., C.S.C.S., a sports scientist, exercise physiologist and nutritionist. “The anterior pituitary produces hormones that become dysregulated if you’re overtraining, don’t sleep well at night, have a poor heat tolerance, or experience something like a traumatic brain injury,” she explains. Exogenous ketones seem to help realign the production of susceptible hormones like prolactin, which can otherwise prevent proper sleep and recovery.
To top it off, it takes very minimal effort for athletes to earn all these gains: “You can still have your cake and eat it too — literally and figuratively,” Scott explains. “Athletes don’t need to be consuming a diet that’s extremely restrictive on food choices or energy sources during exercise, and they can then consume exogenous ketones to introduce yet another fuel source the body can use.”
Johnson says it’s only a matter of time before major American sports stars pick up the training aid — and that we’ll definitely see it in the Olympics. “Basketball and hockey especially have some grueling schedules. Imagine the benefit in-season for back-to-back games on the road?”
So, should I try them?
Johnson estimates that roughly 80 percent of the interest in exogenous ketones on The Feed comes from Europe and about 60 percent of that is from non-elites.
For most amateur athletes, that 15 percent improvement in recovery means you’ll simply feel better after a grueling workout — you’ll have less muscle soreness and stiffness, more energy, better range of motion and sleep better, says Austin.
But that’s not necessarily the score it sounds like. “If you don’t feel terrible after a series of tough training days or a hard race, you’re much more likely to get back out, sooner,” Austin says. “But you might do more harm than good.” Until we understand better how exogenous ketones affect the body and recovery, numbing the alarm doesn’t change the need for rest.
And will they even work for you like they do for the pros? Jury’s still out. Everyday athletes are likely going to respond differently to exogenous ketones, considering just the impact of genetics and training on energy substrate metabolism (how well your body burns other fuel sources) alone, Scott says. And, as with all supplements or performance aids, there are very clearly responders and non-responders. It simply doesn’t work for everyone, he adds.
But most importantly, there are so many other aspects of performance that everyday athletes would be better served to focus on, Scott points out, including but not limited to sleep, diet composition, diet quality, nutrient timing, hydration, training program, rest days, stress management, meditation, visualization and even social relationship quality. “For elites, all these things are taken into consideration and already optimized,” he says. “But I would hate for an amateur athlete to start taking ketones to improve sleep for better recovery when it’s really their stress management that needs to be tweaked.”
The upside: as long as you monitor everything above, all our experts agree, there’s close to no risk in trying.
Where do I start?
Pretty much everyone agrees you shouldn’t be using exogenous ketones to enhance recovery after every hard workout or race. “This isn’t meant for a long weekend ride,” Johnson cautions. “Even if it was really hard and I came home completely bonked and exhausted, I don’t need a ketone ester to feel better at work the next few days.”
Not only will drinking it post-ride regularly lead to overtraining, but, at $37 a bottle, a few bottles a week doesn’t make economic sense for most of us. The effects of exogenous ketones last roughly an hour after ingestion and you’re intended to drink a whole bottle immediately after moving for recovery.
“If a client is having trouble sleeping, I’ll have them drink ketones before bed so their body can catch up on repairs. But it’s important to address the underlying issues of why they’re not sleeping in the bigger picture.”
But when marathon training gets serious and you’re logging 15K, 18K and 12K all within a few days? That’s when you want to take it. “Harder training weeks, multi-day endurance competitions, multi-stage races — I would absolutely be using it after every stage. That level of benefit is enormous,” Johnson adds.
Austin agrees, but adds she’ll also use it sparingly to disrupt recovery inhibitors. “If a client is having trouble sleeping, I’ll have them drink ketones before bed for just a few nights so their body can catch up on repairs,” she says. “But it’s important to address the underlying issues of why they’re not sleeping in the bigger picture.”
And while we have no studies on microdosing (which would be more approachable and more wallet-friendly), Austin says she’s seen some results. “If someone is new to training, that mid-morning fatigue can be debilitating in terms of getting work done, but taking 10 milliliters of ketones can give them an energy boost,” she explains.
Are exogenous ketones safe?
Everyone agrees, given the current state of research, exogenous ketones are generally safe. And the one high-quality product we have on the market now (HVMN) is good to go.
But it’s worth noting that exogenous ketones are currently sold as dietary supplements, which means there’s no oversight by the FDA. As ketones become more popular and more formulas come to market, we’ll inevitably see products packed with both other enhancements and other cost-cutting, potentially dangerous ingredients, Scott says. (The upside: the hefty price of formulas like HVMN will likely come down, too.)
We also don’t know the effects or risks of using it long term — is there a threshold after which exogenous ketones stop being as effective? If your body gets used to the aid in recovery, could it eventually stop being as efficient at rebuilding without it? Do you get any of the neuroprotective benefits of naturally going into ketosis? And, perhaps most importantly, if you’re an ultra-runner or frequent multi-day racer using exogenous ketones for recovery, what nuanced alarm bells are you overlooking?
There are definitely a lot of unanswered questions when it comes to exogenous ketones. But with minimal risk and serious potential gains, we wouldn’t knock anyone for giving a sip.