Mountain Biking: Carbon versus Weight Loss Injections
By Dr Estelle Ivanova, Attorney at Law, Paris, France
Mountain bikers have long spent considerable amounts of money to save just a few grams through lighter frames and carbon components. Weight loss drugs now offer a radically different possibility: shedding kilograms from the rider rather than grams from the bike, potentially at a fraction of the cost.
Since 2026, the World Anti-Doping Agency (WADA) has been monitoring markers of semaglutide and tirzepatide, although neither substance is currently prohibited. For elite athletes, who are already extremely lean, however, the implications may be very different, as weight loss may also involve lean mass, including muscle mass, and could, therefore, come at the expense of performance. For the wider Mountain Bike (MTB) community, the picture is different: weight loss drugs offer a far cheaper way of reducing weight than shaving grams off a bike. Is this the next logical step in weight optimisation, or does it go too far? The story begins in 1988, with a carbon fibre mountain bike frame.
Six euros per gram
In 1988, American manufacturer Kestrel introduced one of the first production carbon mountain bike frames with its MXZ model. Five years later, the 1,288-gram Trek 9900 was considered the world’s lightest production frame. Since then, carbon has turned weight reduction into a battle over every single gram.
The economics are striking. Swiss manufacturer DT Swiss sells its EXC 1200 Classic carbon wheels for €2,499 at 1,644 grams, compared with €749 and 1,916 grams for the aluminium EX 1700 Classic. The carbon version, therefore, costs €1,750 more to save 272 grams — around €6.40 per gram, or more than €6,400 per kilogram. Similar calculations can be made for frames, brakes and drivetrains.
Today, the lightest racing hardtail frames weigh around 800 grams, whilst carbon full-suspension cross-country and marathon frames weigh between 1.5 and 2.5 kilograms — heavier than the 1993 Trek hardtail. In enduro and downhill, weight is less important than stability and control, whilst modern frames must also accommodate wider tyres, greater suspension travel and reinforcement for harder impacts.
With increasingly little weight left to save on the mountain bike — and each additional gram becoming ever more expensive — the next weight-saving revolution may no longer concern the bike, but the rider. And this time, it comes from a syringe.
What the injection really costs
With one subcutaneous injection per week, clinical trials report an average body-weight loss of about 15% with semaglutide and up to 22.5% with tirzepatide. However, weight loss does not come exclusively from fat. A body-composition substudy of SURMOUNT-1 found that approximately 25% of the weight lost with tirzepatide was lean mass, which includes muscle mass. For already lean elite athletes, the trade-off may, therefore, be very different.
For the wider MTB community, the option may initially appear tempting. In Switzerland, a four-week supply of Wegovy (semaglutide) costs around 179 Sw. Frs. (around €191) without insurance coverage — a fraction of the price of a carbon wheelset. Yet it is unclear how long a fit, normal-weight mountain biker would need to use it to lose, for example, two kilograms: the available efficacy data comes from overweight or obese individuals with much greater weight-loss goals, not from lean athletes.
Access is another matter. Insurance coverage is subject to medical criteria, including BMI and associated comorbidities, which a well-trained rider seeking to lose two kilograms for a climb or race would not meet. Anyone seeking the drug outside its medical indication would, therefore, have to pay the full price, obtain a prescription and find a doctor willing to prescribe it. Anyone with the money can buy carbon; a weight loss injection is not so readily available.
Legal, but under scrutiny
Hard to get does not mean it is banned. It is not banned in either elite or recreational sports. Its use is being monitored nonetheless: semaglutide and tirzepatide are under WADA (World Anti-Doping Agency) scrutiny, with the Monitoring Program intended to identify patterns of misuse and inform any future decision on whether they should be added to the Prohibited List.
The broader question of where sport should draw the line between permissible innovation and regulated advantage is not new.
Nike’s carbon-plate shoe, the “Vaporfly,” was also legal at first, until world records began falling one after another and World Athletics introduced technical limits in 2020, including a maximum sole thickness of 40 millimetres for road shoes. Norwegian sports philosopher Sigmund Loland has summed up what this is all about: the question of whether a performance can still be attributed to a person’s talent and effort, or to the technology that they use.
The significance of GLP-1 agonists, which are prescription injectable or oral medicines that promote weight loss, however, goes beyond weight alone. As Olivier Rabin, the WADA Senior Director of Science and Medicine, has observed, they represent a significant shift in weight management: whereas weight loss traditionally required substantial caloric restriction, GLP-1 drugs can facilitate weight loss without the same degree of dietary restriction.
As noted above, WADA is examining whether such substances could ultimately be added to the Prohibited List. Rabin has indicated that, if monitoring in 2026 and 2027 reveals patterns of abuse of GLP-1 agonists in sport, they could be banned before the Los Angeles 2028 Olympic Games.
Weight loss injections act within the body itself. Lighter material only affects the rider from the outside. This is, therefore, about more than just weight: it is about the risk that an athlete takes to become lighter. There has been little research into their use in healthy, lean athletes, and long-term safety data in this population is lacking.
What is certain, however, is that weight loss injections were not developed for sports. In elite sports, any performance benefit remains uncertain; in recreational sports, access is restricted. Carbon, on the other hand, continues to deliver exactly what it was developed for, namely, lightweight yet sturdy components.
For the vast majority, material weight optimisation remains the simpler and safer choice. Ultimately it is for MTB riders to decide for themselves whether the risk of weight loss injections is still worth it.
Dr Estelle Ivanova may be contacted by e-mail at ‘
