Like all sports, cycling is no stranger to training trends, each promising that elusive marginal gain. Some trends are backed by solid scientific evidence, demonstrating tangible performance benefits, while others thrive on marketing hype, team endorsements, and vocal advocates. Regardless of their credibility, these trends quickly permeate the peloton, trickling down to amateur and recreational riders eager to integrate the latest performance-enhancing tools into their ever-expanding regimens.

One such trend that has been impossible to ignore in recent years is ketones. Often seen in small vials or dark liquid shots consumed by elite cyclists post-race, ketones have sparked heated debates despite becoming a staple in the professional ranks. But what exactly are ketones, and more importantly, do they offer any real benefits for the average cyclist?

Understanding Ketones: Endogenous vs. Exogenous

Ketones are not foreign to the human body. In fact, you already have a supply circulating in your bloodstream—just at very low levels. They are produced by the liver when carbohydrate stores are depleted, and fatty acid levels are elevated, a scenario commonly experienced during prolonged endurance exercise. These naturally occurring ketones, known as endogenous ketones, serve as an alternative energy source when glycogen is in short supply.

However, the ketones that have garnered so much attention in the cycling world are not the ones produced by the body but rather those ingested in the form of supplements—exogenous ketones. These typically come in two primary forms: ketone esters and ketone salts, with the former being the more potent (and expensive) option.

The Origins of Ketone Supplementation

The initial interest in ketone supplementation was sparked not by the sporting world, but by military research. The U.S. Department of Defense, in collaboration with Oxford University, sought ways to nutritionally support soldiers operating in energy-depleted conditions. The idea was simple: provide an alternative fuel source that could sustain performance when food rations were limited.

Fast-forward to the 2010s, and the concept of ketones found its way into mainstream diet culture with the rise of the ketogenic diet. This high-fat, low-carbohydrate approach aims to shift the body’s primary fuel source from glycogen to fat, often resulting in weight loss. While the keto diet and ketone supplementation share common principles, their intended outcomes are vastly different—one focuses on metabolic adaptation, while the other seeks to provide an immediate alternative energy source.

Ketones in Endurance Sports: Performance Booster or Overhyped Trend?

The sporting world’s interest in ketones gained traction during the 2012 London Olympics, where UK Sport conducted covert trials on Team GB athletes, including cyclists. At the time, participating athletes were required to deny their involvement due to concerns over potential doping allegations, despite ketones being legal.

The fundamental theory behind ketone supplementation for endurance athletes is that ingesting ketones elevates blood ketone levels, encouraging the body to prioritize fat metabolism while preserving glycogen stores. In theory, this could allow a rider to maintain energy levels longer, particularly in the final critical stages of a race. However, while some studies suggest that ketones may enhance endurance, the majority of research has found little to no meaningful performance benefits. In some cases, ketone use has even been associated with negative effects, such as increased lactate production, gastrointestinal distress, and nausea.

The Controversy and Cost Factor

Despite the inconclusive evidence, ketone use has become widespread among elite cycling teams. Top-tier squads such as Team Visma | Lease a Bike signed sponsorship deals with ketone supplement brands like Ketone IQ in 2024, further fueling the perception of ketones as a must-have performance enhancer.

So why do so many pros use them if the science remains uncertain? One key factor is cost. Conducting large-scale, long-term studies on ketones is prohibitively expensive, mirroring the high price of the supplements themselves—often ranging between £45-£70 for just a few doses. This financial barrier limits the scope of research, leaving many questions unanswered. Meanwhile, governing bodies remain divided on their stance. While the UCI advises against their use, neither the World Anti-Doping Agency (WADA) nor the International Olympic Committee (IOC) have imposed a formal ban. The Movement for Credible Cycling (MPCC), however, continues to push for prohibition due to concerns over unknown long-term health effects and potential performance manipulation.

The Shift to Recovery Enhancement

As research has evolved, the focus has shifted from ketones as an in-race fuel source to their role in post-exercise recovery. Emerging studies suggest that ketone ingestion following intense endurance efforts may enhance glycogen replenishment and stimulate protein synthesis, potentially accelerating muscle recovery. This has made ketones particularly appealing for WorldTour teams competing in grueling multi-day stage races, where rapid recovery is crucial for sustained performance.

Should the Recreational Cyclist Use Ketones?

For riders outside the elite ranks, the consensus among top sports scientists, including Martijn Redegeld and Iñigo San Millán, is clear: ketones offer little benefit. Without meticulously controlled training, nutrition, and recovery strategies, any potential advantage is negligible. Instead, focusing on fundamental elements—optimized fueling strategies, structured training, adequate rest, and overall dietary balance—will yield far greater performance gains at a fraction of the cost.

It’s also worth remembering that the cyclists seamlessly downing ketone shots post-race are part of the sport’s upper echelon. They have access to comprehensive nutrition plans, team support, and financial resources that make ketone use a viable (albeit expensive) experiment. For the high-level amateur balancing training with a full-time job and perhaps relying on supermarket meal deals for convenience, the marginal benefits of ketones pale in comparison to the gains achievable through smarter training, better nutrition, and proper recovery.

Conclusion: The Bottom Line on Ketones

Ketones remain one of cycling’s most debated supplements, with conflicting research and ongoing controversy. While their use in elite racing is undeniable, the lack of conclusive evidence and the high cost make them an impractical option for most cyclists. Until clearer scientific backing emerges, the best investment any rider can make is not in a bottle of ketones, but in perfecting the basics—nutrition, training, and recovery. That’s where the real one-percent gains lie.