"The issue of ketones is more problematic than ever": Clean cycling group slams UCI over ketone inaction

Professional cycling finds itself in the middle of one of its most debated controversies: the widespread use of ketone supplements. The “clean-cycling” group Mouvement Pour un Cyclisme Crédible (MPCC) has publicly criticised Union Cycliste Internationale (UCI) for failing to resolve the ketone issue, leaving the peloton in a prolonged limbo.

A recent statement from the MPCC warned that the UCI’s long wait for results from commissioned studies has become “embarrassing,” and urged a firm stance: either approving use or banning it outright. According to MPCC, the UCI’s impact assessment that had been announced months ago could be delayed until the end of 2025, a timeframe they consider unacceptable given the implications for athlete health and sport credibility.

Despite mounting pressure, the UCI has not imposed a ban, but as of October 2025 it formally advised against the use of ketone supplementation.

Ketones, often marketed as the fourth macronutrient, are said to provide an alternative fuel source for body and brain, sparing glycogen stores and offering endurance and recovery advantages. They can be achieved through physiological ketosis (fasting or zero-carb diets) or by ingesting exogenous ketone esters or salts. Claims range from improved endurance and late-race explosivity to faster recovery and enhanced mental focus.

Cycling’s embrace of ketones accelerated after several top teams began publicly associating with major supplement brands, such as Visma Lease a Bike and Soudal - Quick-Step. According to insiders, in events such as the last Tour de France, up to 75 % of the peloton may have used ketones. Because ketone supplements remain legal (not on the WADA banned list), teams and riders are left to decide individually whether to use them.

Within the MPCC, tension is rising. Their bulletin argues that the UCI must resolve the uncertainty. “The issue of ketones is more problematic than ever. Either the UCI is certain that the use of ketones is acceptable and must make this known… or it is not, and must state loud and clear that the institution does not recommend their use, or even that it prohibits it.”

Meanwhile, the ketone supplement industry has exploded beyond professional cycling. Marketing campaigns target not only athletes but also everyday people, promoting ketones as “mental boosters,” “fuel for endurance,” and “performance enhancers.”

Even if the UCI rules them out, authorities will face enforcement challenges: ketones are widely available as nutritional supplements, not forbidden substances, which makes detection much more difficult. The debate, thus, touches on deeper issues: how to handle performance-enhancing supplements legally available to all, without undermining fairness, health, and credibility.