Train Your Gut: Harness More Energy During Races

6 min read

Updated: 13 February 2026

Many people experience stomach issues when trying to consume fluids and energy during long sessions and competitions—especially when the intensity is high or the heat is overwhelming. This article discusses how you can "train your gut" so that the intake of sports drinks and carbohydrates becomes both more tolerable and more effective. The main question is how to increase tolerance and improve the stomach's handling of energy and fluids without discomfort. The conclusion is that the gut can be trained: by practicing intake in controlled sessions, adjusting your diet before periods of higher intake, and using a good carbohydrate mix, you can reduce issues and get more out of your energy during performance.

Don't try anything new on race day

Do you also own a pair of dress shoes that only make an appearance for special events, like weddings and similar occasions? Then you might have noticed how a little wear can lead to them rubbing in unfamiliar spots. It's usually tolerable — these events don't demand much activity. You're mostly sitting, chatting, and enjoying yourself, and the minor chafing is forgotten, perhaps with the aid of a drink or two, and those shoes are tucked away until next time.

Fast forward to your decision to wear these uncomfortable orthotics on Midsummer, forgetting the previous minor irritations. This time, small blisters are inevitable. After participating in activities like Irish Christmas and rounders, you won't dare take the shoes off as those small blisters have worsened.

"Don't try anything new on race day," everyone advises, and it's an excellent rule to keep in mind. In this article, we will discuss how to train your gut so it becomes not just more stable but also more efficient.

Boost Your Tolerance with Controlled Exaggeration

There's always someone somewhere who has accomplished something that most of us find mind-boggling. For instance, the world record for the number of hot dogs eaten in 10 minutes is an astounding 72. This is undoubtedly an unusual record, but it illustrates just how adaptable our stomach can be to extreme challenges. When these "athletes" train for a competition, one strategy is to drink large amounts of liquid weeks in advance. By practicing consuming extreme amounts of liquid and food in a short time, tolerance increases, and you don't feel as full. The stomach is incredibly adaptable.

One of the challenges athletes face is feeling bloated and waterlogged, even with relatively low liquid intake. So how do we train our gut as athletes?

Hydration in Heat: Why the Gut Needs to Keep Up

Through sweating, the body can maintain high intensity even in really warm conditions. But to sweat effectively, there must be plenty of fluids available. One of the highest amounts of sweating recorded during activity was by Alberto Salazar during the 1984 Olympics, where he reportedly lost 5.43 kg during the marathon despite consuming 1.88 liters of fluid. This results in a total sweat loss of 3.71 liters, corresponding to a weight loss of just over 8 percent. In long events like an Ironman, optimizing fluid intake to maintain as good a balance as possible becomes a major challenge. Therefore, training should include several sessions with higher fluid and energy intake to prepare you for the challenge. This can vary greatly for each individual, but if you manage to consume just over 1 liter over 2–3 hours of activity, you'll have a solid foundation to rely on!

Carbohydrates and Gastric Emptying

The way your body adjusts to what it's exposed to forms the basis of training. In a study we reviewed, the impact on gastric emptying of glucose and fructose was analyzed when a standard diet was supplemented with 440 grams of carbohydrates per day over 4–7 days. The carbohydrates were consumed separately in liquid form as a drink, with the intake evenly distributed throughout the day.

Study Findings: Faster Emptying with Higher Intake

The result was not entirely unexpected: participants reported significantly faster gastric emptying of both glucose and fructose in subsequent tests.

Dietary glucose supplementation accelerated gastric emptying of glucose (50% emptying time 82 +/- 8 min vs. 106 +/- 10 min, p = 0.004) and fructose (73 +/- 9 min vs. 106 +/- 9 min, p = 0.001), resulting in 23% faster emptying.

The body had become significantly more efficient at managing energy intake.

Adaptation also applies to fat

The same phenomenon was observed in a study where the diet was shifted to a more fat-rich composition over two weeks. In this study, gastric emptying was faster when the high-fat group consumed a fat-rich diet. The body specifically adapted the emptying to the composition of carbohydrates/fat/protein it was most accustomed to.

Our body is incredibly adaptable in a relatively short time. So, what you eat more of, the body becomes better at absorbing. Therefore, adjusting your diet leading up to performance can be one of your key tactics to keep your stomach calm.

Practice Your Race Plan

In a study involving well-trained runners, researchers examined how participants managed their fluid intake in relation to their sweat loss. Participants drank approximately 500 ml per hour while running for 90 minutes at 80 percent of their maximum heart rate, repeating the test six times. Though not super intense, the regimen was still demanding. Results indicated that aligning fluid and energy intake with sweat loss primarily enhanced the gut experience. Runners felt less bloated or full-stomached during the final test, having adapted to the regimen compared to their initial experience.

Ease the Gut and Stomach

Tolerating more energy and fluids is achievable, especially if the carbohydrate composition is optimized. An intensive study in this area was conducted in 2005 where well-trained cyclists consumed 2.4 g/min (144 g/h) of either glucose alone or a mix of glucose and fructose. The result showed that when they consumed glucose alone, absorption stopped at around 1 g/min, while it increased to 1.75 g/min with glucose:fructose. There is extensive research in this area about which carbohydrate composition is most beneficial. If you're interested in a deeper exploration on the subject, you can find our article on optimal sports drink here.
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Boost your oxidation by training with energy

If you want to maximize your performance and reduce the risk of gut issues, the best strategy is to train with energy in the weeks leading up to your event (in addition to the strategies mentioned above). In a study by Cox et al., skilled athletes were divided into two groups. They trained either with or without energy for 28 days. The weekly volume was high (16 hours), and as a result, both groups improved in subsequent tests at the end of the intervention. Participants who trained with energy also had a higher carbohydrate oxidation than the group that trained without. You can read more about this study in our previous article here.

Summary: Build Your Iron Stomach

Your body adjusts to what it’s exposed to. If you train and live in a certain way, your body will respond accordingly. If you're among those who feel discomfort from fluid intake or energy, we suggest simply training your weakness.

Your gut becomes more stable, turning what was once a concern into your confidence. Below, you’ll find a figure from Jeukendrup, summarizing different methods to train the gut for performance. With a bit of curiosity and training, you can claim to have an iron gut too!

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