What is gut training?

Gut training means regularly practising your event-day nutrition strategy during training. By consuming carbohydrates and fluids on the bike, you help your digestive system become accustomed to processing fuel while your body is under physical stress. Research suggests that repeated carbohydrate intake during exercise may improve gastric emptying, carbohydrate absorption and tolerance while reducing gastrointestinal discomfort (Jeukendrup). The goal is not to consume as much as possible. It is to gradually become comfortable with the amount of fuel your target event requires.

How your gut limits performance

Your carbohydrate stores only go so far on longer rides. Taking on fuel helps maintain energy availability, but being able to carry enough is a very different thing from being able to tolerate and absorb it. When riders start feeling sick or bloated they often stop eating altogether. Their cardiovascular fitness may still be strong, but their fueling system can no longer keep up with the demands of the effort.

Research involving 51 cyclists and triathletes found a clear relationship between carbohydrate intake and endurance performance, with performance improving as intake increased, with an estimated optimal intake around 78 grams per hour (Smith et al.). More recent data from professional cycling tells a different story. On-bike intake has climbed from 30 to 60 grams per hour before 2010 to 120 grams per hour and higher today, with some WorldTour teams targeting even more on the hardest stages.

These numbers are not a starting point for most riders. Reaching 120 grams per hour requires months of deliberate gut training, gradually building tolerance through consistent practice. The right amount depends on how long and how hard you are riding, your experience level and how well your gut currently handles fuel under pressure.

What does the research say?

In one study, endurance runners completed two weeks of repeated carbohydrate feeding during exercise. The carbohydrate groups reported fewer gastrointestinal symptoms and improved running performance compared with the placebo group (Costa et al.). A second study found that two weeks of gut training reduced gastrointestinal discomfort and carbohydrate malabsorption. Participants also covered more distance in the final exercise test after the intervention (Miall et al.). However, the evidence is not universal. A study of highly trained endurance athletes found only minor effects from a short-term high-carbohydrate diet and gut-training intervention (King et al.). This suggests that athletes who already tolerate high carbohydrate intakes may have less room to improve. Most gut-training studies have also involved runners rather than cyclists. The findings are promising, but they should be applied as practical guidance rather than a guaranteed performance formula.

How to train your gut

Start with what you tolerate

Estimate how much carbohydrate you currently consume during long rides. Begin with an amount that already feels manageable instead of copying the strategy of a professional rider.When that amount feels comfortable, increase it gradually. For example, progress from 40 to 50 grams per hour before attempting 60.

Practise during relevant workouts

Easy endurance rides are a good place to begin. As your target event approaches, test your strategy during longer and more intense sessions. Your gut needs experience processing fuel when you are riding hard, becoming warm and accumulating fatigue, not only when conditions are comfortable.

Eat little and often

Consuming a large amount at once may increase discomfort. Spread your intake across the hour by drinking regularly and taking smaller portions of carbohydrate at consistent intervals. Do not wait until you feel hungry or low on energy. By then, it may already be difficult to recover the deficit.

Test the complete plan

Practise with the same drinks, gels, chews, bars or foods you intend to use during the event. Also test how much water you need with each product. Consider the practical details:

• Can you open the packaging while riding?

• Can you carry enough fuel?

• Where can you refill?

• Does the flavour remain appealing after several hours?

A nutrition strategy must be both scientifically sound and realistic to execute.

Record the results

After key rides, note:

• Carbohydrate and fluid intake

• Products used

• Ride duration and intensity

• Weather conditions

• Energy levels

• Any nausea, bloating or cramps

This can help you determine whether discomfort is connected to the quantity, timing or type of fuel, or to other factors such as intensity, heat and hydration.

Train the complete system

Cycling performance is not determined by FTP alone. Your legs must produce power, your cardiovascular system must deliver oxygen and your digestive system must keep supplying fuel. A strong engine still needs a reliable fueling system. Start with an amount you tolerate, increase it gradually and practise during rides that resemble your target event. By race day, eating and drinking should feel like part of your routine, not an experiment. Persistent or severe symptoms, including repeated vomiting, intense abdominal pain or blood in the stool, should be discussed with a qualified medical professional.

Works Cited

Costa, Ricardo J. S., et al. “Gut-Training: The Impact of Two Weeks Repetitive Gut-Challenge during Exercise on Gastrointestinal Status, Glucose Availability, Fuel Kinetics, and Running Performance.” Applied Physiology, Nutrition, and Metabolism, vol. 42, no. 5, 2017, pp. 547–57. doi:10.1139/apnm-2016-0453.

Jeukendrup, Asker E. “Training the Gut for Athletes.” Sports Medicine, vol. 47, suppl. 1, 2017, pp. 101–10. doi:10.1007/s40279-017-0690-6.

King, Andy J., et al. “Short-Term Very High Carbohydrate Diet and Gut-Training Have Minor Effects on Gastrointestinal Status and Performance in Highly Trained Endurance Athletes.” Nutrients, vol. 14, no. 9, 2022, article 1929. doi:10.3390/nu14091929.

Miall, Atlanta, et al. “Two Weeks of Repetitive Gut-Challenge Reduce Exercise-Associated Gastrointestinal Symptoms and Malabsorption.” Scandinavian Journal of Medicine & Science in Sports, vol. 28, no. 2, 2018, pp. 630–40. doi:10.1111/sms.12912.

Smith, Johneric W., et al. “Curvilinear Dose-Response Relationship of Carbohydrate (0–120 g·h⁻¹) and Performance.” Medicine & Science in Sports & Exercise, vol. 45, no. 2, 2013, pp. 336–41. doi:10.1249/MSS.0b013e31827205d1.