Ketones have courted controversy since The Mail on Sunday disclosed that 91 athletes were used as guinea pigs in the run-up to the London 2012 Olympics to test the potential performance effects of this synthetic energy source.
Until the past few seasons, WorldTour teams and riders have remained stoically tight-lipped, whether they were using them or not – especially Team Sky, who publicly and repeatedly denied usage.
This stubborn silence fuelled scepticism in a sport still reeling from the Lance Armstrong saga, despite ketones never being on the WADA (World Anti-Doping Agency) prohibited list.
The Mouvement Pour un Cyclisme Crédible (MPCC) advised its members not to use them due to the unknown long-term health impact.
They also called on cycling’s governing body for clarity. “We’re awaiting the result of a UCI study into ketones,” the MPCC told me several years ago. And again last year. And earlier this year.
A UCI press release landed in October 2025 – finally, ketone clarity. Not quite. “There is no compelling evidence that ketone supplements enhance performance or recovery, so the UCI see no reason for them to be used. Therefore, the UCI do not recommend the inclusion of such supplements in riders’ nutritional plans.”
On the face of it, the UCI's stance is plain. But it soon becomes clear that its summation of this substance, originally developed by scientists at Oxford University with $10 million of funding from the American Department of Defence so US Special Forces could operate for longer behind enemy lines with fewer rations, couldn’t have been more opaque – there was no comment on long-term health and no reference to their own study.
And who tasked the UCI with nutritional advice? We contacted the UCI for further detail, to speak to whoever conducted the study that it didn’t reference in the release.
The press officer replied: “Please be informed that this study is currently with a scientific journal and is expected to be published soon. While we do not have a confirmed publication date, we will share the article link and the author’s contact details with you once it becomes available.” We batted back with, “Understandably, there are many questions off the back of the press release.
Firstly, if the study is yet to be released, why are the UCI making a statement?” “We are awaiting the publication of the study, came the response. As soon as it is released, we will share the publication link along with relevant contact details for the authors.”
And so on.
So, despite the brevity and lack of evidence, the UCI feels taking ketones is a waste of time. Which must have had the likes of Ketone-IQ, used by Visma–Lease a Bike, and KetoneAid, used by Soudal Quick-Step, turning to their lawyers. Then again, the UCI does have a point that evidence for their use is far from equivocal.
But that can be said about everyday supplements used by cyclists all around the world – multi-vitamins for example – and the UCI hasn’t delivered a verdict on those.
So, is there a benefit?
That’s the politics, which we suspect will run and run. But what of the studies into ketones and cycling performance?
What is the general consensus from those? That’s where we turn to Sebastian Sitko, a sport scientist and lecturer at the University of Zaragoza in Spain.
In 2024, the journal Physiologia published Sitko’s work, ‘The role of exogenous ketones in road cycling: evidence, mechanisms and performance claims’. Within, his meta-analysis took a deep dive into the published literature.
“The potential benefits of ketone body supplementation in endurance sports like cycling are multifaceted, spanning metabolic, physiological and cognitive domains,” he concluded in his paper.
“However, despite the growing interest in ketone supplementation, the current science applied to the practical field is limited by inconsistent findings, individual variability and a lack of long-term data.”
In short, there’s an uncertainty around their benefits. But that doesn’t mean they don’t work. As Sitko highlights, it’s an individual thing and, like most facets of training and nutrition, comes down to whether someone is a ‘responder’ or ‘non-responder’.
“Evidence for its use points to a mix of phenotype [observable characteristics of when nature meets nurture] and current metabolic state,” he says.
“A rider’s baseline metabolic health (insulin sensitivity, level of fat), recent diet (carbohydrate availability, keto- adaptation), gut absorption, gender and training status all matter.”
“The delivered BHB exposure (not just the dose) is a big determinant of response,” he adds. BHB is beta-hydroxybutyrate, a type of ketone. Its vessel tends to be either an ester or salt, with the evidence stronger for ester use because ketone content tends to be higher.
“Genetics likely plays a role, but robust genotype response links in athletes are still lacking,” says Sitko. “In short, who you are (metabolic phenotype) and what state you’re in (glycogen-heavy, fasted, recent training) are the main practical predictors.”
Mechanisms of improvement
If you respond, what does that mean? Potentially riding longer and stronger, fighting fatigue and delivering high-intensity moments when needed.
“The most plausible mechanism why is due to sparing glycogen,” says Sitko. “Ketone bodies can be oxidised efficiently by the working muscle and theoretically reduce reliance on carbohydrate, which could preserve muscle glycogen during very long efforts or in low-glycogen states.”
That physiological promise has clear mechanistic rationale, says Sitko, but enjoying consistent race benefits has proven tricky because cycling performance is the product of numerous interacting systems.
For instance, fuel availability, neuromuscular function, pacing, thermoregulation and gut tolerance to ketones.
There’s also an argument that ketones raise blood acidity, which is exactly what you don’t want when exercising hard. “The major problem is that small metabolic gains often disappear when translated into whole-race conditions,” Sitko continues.
“Laboratory protocols, participant feeding state, ketone dose and how it’s delivered, and whether carbohydrate is co-ingested all change the metabolic context, so the same ketone drink can produce different outcomes across studies and athletes.”
In essence, like any mooted performance-enhancer, while it might give a physiological boost in the controlled setting of a laboratory, which can be measured easily, the same can’t always be said once it’s in the dynamic amphitheatre of racing. And if it does, there are too many variables to pinpoint ketones as the game-changer.
After researching this area over several years, we’d presumed that the time it took the UCI to make a statement came down to delays while it pored over recent studies that show a rise in circulating erythropoietin (EPO) in the body.
EPO is a hormone that naturally produces red blood cells but, as Lance and co showed, can also be taken exogenously (primarily by injection) to raise levels artificially.
It’s why, under section S2.1 of WADA’s Prohibited List, entitled, ‘Erythropoietins and agents affecting erythropoiesis’, EPO and other drugs that elevate levels of EPO are banned. Then again, not every method of boosting red blood cells is outlawed. Altitude training, for instance.
“There isn’t solid evidence that these temporary EPO rises translate into sustained increases in red-cell mass or haematocrit (which would require repeated exposure and time for erythropoiesis),” says Sitko.
“In short, EPO signalling equals possible stimulus, but increased red blood cell mass and measurable performance gain is not established in humans with current data. That makes any anti-doping or performance claims premature.”
Will the UCI’s press release sound the death knell for ketone use in professional and recreational cycling? It’s doubtful, especially when recent research suggests its benefits stretch beyond the (still debated) physical.
Can ketones slow brain ageing?
As Sitko mentioned earlier, studies show that ketones potentially have an impact on “cognitive domains”. Again, the evidence isn’t conclusive, but it is compelling, especially for those who are approaching their mid-40s.
According to research in the journal Proceedings of the National Academy of Sciences, our “brain-network stability” doesn’t follow a linear path of decline.
Instead, it’s non-linear with distinct landmarks of acceleration and plateauing, with the human brain ageing much faster from the age of 44 before levelling off at 67.
The researchers hypothesised that neuronal metabolic stress, such as increased insulin resistance and impaired glucose uptake, leads to a nudge in age-related cognitive decline.
Or it would without drinking a bottle or two of ketones, for they discovered that administering this ‘super- fuel’ delivered an extra energy source that sidestepped the issues caused by this metabolic stress to protect the brain from deterioration.
They warned that the intervention would only prove effective before the neurons fall off a cliff – in other words, start in your mid-40s – and stressed that further research was needed to confirm or disprove the mechanisms at play.
That said, it’s the latest study of many that suggests ketones could be a cognitive lifesaver because of their ability to deliver energy when the insulin system’s struggling.
Because the brain makes up 20% of your daily energy needs each day, the mechanism adds up.
Where does that leave us? Arguably, where we were before the UCI’s press release – in ergogenic limbo. Research shows that performance and recovery can benefit from ketones. It also shows that performance and recovery aren’t impacted by ketones.
As ever, it’s an individual thing whether it works – or you believe it works (placebo is a feature in itself).
But it’s clear that for most recreational cyclists, consistent riding and staying healthy via a wholesome diet are much higher up the performance ladder than any supplement.
Will we ever know if ketones work or not out in the field? Sitko thinks so. “Serial blood metabolomics can reveal individual metabolic fingerprints and identify who benefits from ketone exposure and under which conditions,” he says. “This supports precision nutrition but research is still in its early phase.”
