When endurance athletes think about gut training, they usually focus on practising their race fuelling strategy during long training sessions. While this is important, it’s only part of the picture.
Gut training doesn’t just happen during training — it also happens through your everyday nutrition.
Your digestive system adapts to what it is regularly exposed to. Just as muscles adapt to training load, the gut can adapt to the nutrients and quantities it processes. For endurance athletes, this is particularly relevant for carbohydrate intake, which is often consumed in large amounts during races and long training sessions.
Gastrointestinal Issues in Endurance Athletes
Gastrointestinal (GI) symptoms are common in endurance sport. Many athletes experience issues such as:
- bloating
- stomach cramps
- nausea
- reflux
- diarrhoea
- gels or sports drinks “sitting” in the stomach
These symptoms often occur when athletes try to consume more carbohydrate during exercise than their gut is accustomed to handling.
Research suggests that repeated carbohydrate exposure can support adaptations in the digestive system, including increased intestinal carbohydrate transport capacity and improved carbohydrate absorption during exercise. These adaptations can help athletes tolerate higher carbohydrate intake with fewer gastrointestinal symptoms (Jeukendrup, 2017).
Why Daily Nutrition Helps Train the Gut
While practising race fuelling during training is essential, daily nutrition also contributes to gut training.
Regular carbohydrate intake across the day exposes the digestive system to carbohydrate more consistently. Over time, this may support the gut’s ability to process and absorb carbohydrate efficiently when exercise intensity increases.
Diet composition also affects the gut microbiome, the community of microorganisms that live in the gastrointestinal tract. A varied diet containing sufficient carbohydrate and fibre supports microbial diversity, which may play a role in digestive health and tolerance during exercise (Clark and Mach, 2016).
For athletes aiming to increase carbohydrate intake during competition, both in-session fuelling practice and consistent daily nutrition are important.
Frequently asked questions
Gut training refers to gradually adapting the digestive system to tolerate carbohydrate intake during exercise by regularly practising fuelling strategies in training.
Gastrointestinal symptoms often occur when athletes consume more carbohydrate or fluid during exercise than their gut is adapted to processing.
Yes. Regular carbohydrate intake and overall diet composition can influence digestive adaptations and the gut microbiome, both of which affect fuel tolerance during exercise.