Cycling as a weight loss injection: Quick success without starving yourself - what's the story?
Carola Felchner
· 17.01.2026
"There are no shortcuts to worthwhile goals," the American opera singer Beverly Sills is said to have once said. What she may have been referring to the training of her voice also applies to sport in terms of the power-to-weight ratio, the ideal ratio of power to body weight on the bike: the former requires training, the latter requires diet and controlling the number on the scales. No improvement without discipline. At least that was true until recently. Because since 2018, losing weight by injection has been permitted in the EU: at that time, the European Union authorised the substance semaglutide for weight loss. This is the active ingredient in the now infamous weight loss injections Ozempic and Wegovy, among others, which are enjoying exploding popularity in this function: according to the information service Statista, Ozempic is now the second best-selling drug worldwide with gross sales of 16.1 billion euros.
Simply lose weight by syringe?
Getting and staying slim with the help of a weight loss injection without starving yourself and changing your diet - that sounds tempting. Even for athletes in disciplines in which low body weight provides a performance and competitive advantage, such as road cycling. Because "in theory, losing weight increases the relative oxygen uptake. This is an important marker of physical performance and is crucial for high performance in cycling, especially uphill," explains Dr Stephan Prettin, senior physician at the Institute of Exercise and Occupational Medicine at the Freiburg University Medical Centre. Semaglutide can help shed a considerable amount of weight: studies report an average weight loss of 10 to 15 per cent thanks to the active ingredient. This can mean a considerable advantage on the bike and can decide between victory and second place.
In addition, says sports and nutrition physician Stephan Prettin, there are indications in studies that Ozempic can improve the ejection capacity of the heart. This describes how much blood the heart pumps into the circulation per minute and therefore determines how much oxygen reaches the working muscles, how quickly lactate is removed or how quickly the legs recover after intensive intervals.
However, these data were collected on patients suffering from diabetes mellitus or heart failure. There is currently hardly any reliable scientific data for people who are active in sport. While no professional cyclist has yet publicly admitted to using semaglutide, there are an increasing number of articles and videos from ambitious amateur cyclists who are experimenting with the active ingredient. Semaglutide is not actually intended for weight loss. Instead, drugs containing this active ingredient were developed to treat type 2 diabetes and obesity. This is because semaglutide is a so-called GLP-1 receptor agonist. Put simply, this is a substance that imitates the hormone GLP-1 in the intestine and binds to the corresponding receptors. This endogenous hormone plays an important role in glucose metabolism and in regulating the feeling of satiety.
Semaglutide reduces appetite
Among other things, semaglutide lowers blood sugar levels directly by releasing insulin and inhibiting the formation of new sugar in the liver. "Indirectly, it also regulates blood sugar levels by causing the stomach to empty more slowly and making you feel fuller for longer," explains Stephan Prettin. Semaglutide also reduces appetite by acting on the satiety centre in the brain. Less hunger normally means eating less. This reduces calorie intake - and if you consume less energy than you use, you lose weight. Thanks to the absence of blood sugar spikes, there are also no cravings that could cancel out the calorie deficit with a flash of food. What was intended for the original purpose of Semaglutide and is important for the success of the therapy is not necessarily suitable for achieving a competition weight as easily as possible and without a targeted or controlled diet.
Attention, lack of energy!
"It makes a considerable difference whether an endurance athlete such as a racing cyclist or a predominantly inactive person takes these supplements, especially due to the different energy metabolism and carbohydrate consumption," warns the sports and nutrition expert. This is because racing cyclists burn a lot of energy during training and in competitions, especially in the form of carbohydrates. If you consume too few calories because semaglutide curbs your appetite, you can manoeuvre yourself into a relative lack of energy before, during and after (long) training sessions. As a result, performance slumps. In addition, the body may regenerate less well after exercise, making it less able to adapt to the training stimulus.
"The bottom line is that the use of semaglutide can lead to a decrease in performance, and we haven't yet talked about the potential side effects," explains Stephan Prettin. These, in turn, should not be underestimated.
Side effects
Athletes, especially endurance athletes, are more likely to experience gastrointestinal complaints such as nausea, vomiting, diarrhoea, abdominal pain and constipation when taking semaglutide. One of the reasons for this is that blood shifts from the intestines to the working muscles during endurance exercise and the bent-forward posture on a racing bike puts pressure on the gastrointestinal tract, which empties only slowly. This is a very bad way to train properly or to absorb (and retain) sufficient energy.
There is also a risk of dehydration due to gastrointestinal complaints and reduced food and fluid intake. And: "The slower gastric emptying can impair energy intake before and during training and thus lead to deficiencies. Although the appetite-suppressing effect of semaglutide leads to weight loss, it can also cause insufficient calorie intake, which favours muscle weakness, muscle breakdown and a reduction in resilience," says sports physician Prettin, which is in line with current scientific findings, such as those of a study from 2024, which found that muscle loss caused by the GLP-1 receptor agonist was 0.8 per cent higher than that caused by the natural ageing process.
Semaglutide can also have a negative mental impact, for example in the form of concentration problems, mood swings and irritability, dizziness and fatigue. "The increased control over eating behaviour can also lead to additional mental pressure, fear of loss of performance or even eating disorders in some athletes," warns the internist, sports and nutrition specialist.
The anti-doping authorities have also already become aware of the "wonder substance". Semaglutide is not classified as a doping agent - and is therefore banned. However, since 2024, the active ingredient has been on the list of substances that the World Anti-Doping Agency (WADA) monitors to track whether and how it is used in and out of competition. This means that athletes are also tested for semaglutide during doping tests, albeit (still) without consequences.
Better the conservative way to your dream weight
Dr Prettin believes that the conservative route to the dream weight is better for endurance athletes than the shortcut via a weight loss injection anyway: "It is important to eat a balanced, energy-controlled and high-fibre diet with sufficient micro and macronutrients that covers the high energy requirement but creates a slight calorie deficit in order to reduce fat without losing muscle mass. In addition, targeted strength training to protect the muscles," he advises. Depending on your ambition and performance level, professional nutritional counselling may be useful and, adds Stephan Prettin: "As a nutritionist, I would also always advise against setting goals that are too utopian in too short a time. Longer-term strategies with a realistic goal work best."
Dr Stephan Prettin is an internist, sports physician, nutritionist and altitude medicine specialist. He works as a senior physician at the Institute for Exercise and Occupational Medicine at Freiburg University Medical Centre and has been professionally and privately involved in cycling for decades.
