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How to stop stomach problems from sabotaging your race

Gut issues are reasonably common among endurance athletes. More than 60% of athletes report gastrointestinal symptoms in longer, ultra-endurance events. Symptoms like nausea, cramping, bloating, side stitches, and frequent toilet stops can negatively impact an athlete’s performance. Avoid these mistakes to minimise your risk of gut distress sabotaging your race. 

Mistake #1 - Not training the gut

Just like your legs, lungs and heart, your gut is trainable. You can train your stomach to tolerate, absorb and digest food more efficiently while moving. 

To achieve this, it is crucial to practice and get used to consuming the same type, quantity and frequency of food you’re planning to eat on race day. It’s not only about trying an energy gel during a run and assuming that eating five will also work. 

Mistake #2 - Not hydrating well

Your gut needs water to assist with nutrient absorption and digestion. By being severely dehydrated, you’re compromising your performance and ability to tolerate food. So it’s no surprise that gut issues tend to exacerbate during races conducted in hot conditions. 

Ensure you drink fluids regularly, especially when eating energy-dense foods like gels or bars.

Mistake #3 - Using the wrong type of carbohydrate 

There are different types of carbohydrates or sugars, each of which your body absorbs differently—some at a slower rate than others. On average, your gut can absorb 1 g of glucose per minute. This is why many nutrition recommendations suggest staying around 60g of carbohydrates per hour so your consumption matches your absorption rate. However, it’s been shown that combining different types of carbohydrates can increase the absorption rate to up to 1.5 g/min. Using a ratio of 2:1 glucose: fructose. Being aware of this, many sports products are now developed using this ratio to enhance gut absorption but not all of them. 

If you have this ratio out of balance and consume more carbohydrates than your gut can absorb, your stomach will likely suffer. 

Mistake #4 - Consuming sodium in inadequate quantities

Besides supporting electrolyte balance and hydration, sodium plays a role in food absorption. However, too little or too much can be distressful for your gut and cause issues on race day. 

Mistake #5 - Eating the wrong food before the event

Fibre and fat are elements you must keep in check in the lead-up to your main event. They both slow gut transit, and eating them too close to the race can mean that your body will still be processing them while trying to go on with your event. 

If you struggle with food allergies or intolerances or still haven’t figured out what is causing your gut upset, I encourage you to seek professional help. Understanding the cause of these issues and implementing a plan to manage them will make your training and race experience more enjoyable. 

The final remarks

You can reduce the likelihood of stomach problems ruining your race. As an endurance athlete, planning and practising your nutrition benefits your performance and reduces the risk of gut issues interfering with your race. 


Burke, Louise, Vicki Deakin, and Michelle Minehan. "Exercise-induced gastrointestinal syndrome, gastrointestinal disorders, food intolerance and allergies." Clinical Sports Nutrition. (2021).

Costa, Ricardo JS, 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 42.5 (2017): 547-557.

What are the most effective supplements for triathletes and runners?

For many athletes, it’s hard to think of nutrition without supplements. Unfortunately, the use of supplements across the athletic population is significantly larger than the number of proven effective supplements. That’s why here’s a summary of those supplements with enough evidence of enhancing performance for endurance athletes. 

As an endurance dietitian, I think of supplements as the ‘cherry on top. It doesn’t matter how many cherries you put on your cake, it is half-baked, and some key ingredients are missing, neither the taste nor consistency will be appealing. Relying on supplements to make up for a poor diet is the same. Without the nourishing environment of a solid nutrition and training foundation, most supplements will be useless. 

Sports foods

Products such as sports drinks, energy gels, chews, bars and electrolyte mixes fall within this category. 

The purpose of these products is to supply the athlete with a convenient form to consume a particular nutrient. In many cases, this nutrient is carbohydrates. 

Since endurance athletes rely on carbohydrates as their primary fuel source, these supplements are very relevant. Some key aspects to consider when choosing these products are:

Suggested use: 

Events that benefit the most:



Caffeine is a well-known stimulant with well-established benefits in sports performance. For endurance, caffeine supplements support alertness and decrease perceived effort. Additionally, caffeine promotes fatty acid oxidation helping the body use fat as an energy source. 

Suggested use:

Events that benefit the most:



Dietary nitrate enhances nitric oxide availability. This, in turn, supports exercise performance by improving muscle economy, mitigating fatigue and positively impacting cardiorespiratory performance. 

Supplementation with nitrate has been associated with improvements of 4-25% in exercise time to exhaustion and 1-3% in time trials with less than 40 min duration. 

Suggested use:

Events that benefit the most:


Final remarks 

By now, you may be wondering, “is that it?”. “Why does my supplement shop has many more items than you just mentioned?”. 

Unfortunately, the world of nutrition supplements is inundated with products that rarely offer the benefits listed on their labels. Many of these products go to market with little to no evidence of their efficacy, putting the athlete’s wallet and, most importantly, their health at risk. 

Remember, always consult with your health or nutrition professional before using any supplement and only consume products that have been batch tested for banned substances. 



There’s an equation that I love referring to when I think of endurance nutrition and performance.

QT x PA = IP

where QT = Quality training sessions, PA = Physiological adaptations and IP = Improved Performance

At its core, the purpose of training is to stimulate physiological adaptations in your body, such as developing muscle mass, increasing pulmonary capacity, improving blood flow, developing resistance, etc. These adaptations allow your body to be more efficient, faster and stronger, which translates into better performance and results.

This means that targeting your endurance nutrition into completing quality training sessions and promoting your body’s training adaptations will bring more benefit to your performance in the long term.

Fuelling quality training sessions

I don’t know about you, but my ideal training session looks something like this: Even before the warm-up, my body feels ready to get going, I’m able to meet the targets for each of the sets, and even though they don’t feel easy, I’m able to stay consistent throughout the session. Then, when I’m done with the cool-down, I’m ready to go home, enjoy a nice shower and get on with my day.

Whereas on the opposite side, my worst training sessions had looked something like this: I felt sluggish during the warm-up, I even needed the first set to get into the pace required, and by the time I was on the second last set, I was already struggling and have dropped the pace significantly, the cool-down feels more like dragging my body to the car and by the time I get home I’m only looking forward to being on the couch.

The main difference between one session and the other is that my body was well-recovered and energised in the first one. Whereas in the second, I didn’t have enough energy, and my body was not fully recovered.

You must ensure your body is well-nourished and energised to get quality training sessions. This is not something that drinking a Red Bull thirty minutes before warm-up will fix.

What you eat before, during and after your training session directly impacts the quality of that training session. Not all sessions have the same objective. Therefore you should not fuel all sessions the same way. Download my free fuelling guide with specific endurance nutrition recommendations for different training sessions. 

Promoting the training adaptations

Above else, your body prioritises survival. This means that the body uses the energy you consume for core functions and uses whatever is left for non-essential activities such as your daily run or your time at work. 

When the energy is insufficient, your body tries to spare as much as possible for essential functions and finds ways to save energy from the non-essential ones. Have you ever felt unable to concentrate at work, sleepy, or unwilling to train at all? These are examples of your body’s attempts at saving energy. 

A well-nourished and energised body is a body that is consistently fuelled throughout the day, receives vital nutrients when they are needed the most and has all essential nutrients available to thrive.

When the energy is sufficient, and all the essential nutrients are present in your diet, your body can target non-essential functions, such as promoting the training adaptations that allow your body to become more efficient, faster and stronger. 

Final remarks

As you can see, what you eat on race day is very important for that day to be successful. However, you are leaving a lot on the table by not looking at your sports nutrition months ahead of your main event. What you do day by day, week by week, will give you the most significant advantage. 

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Len Hartley

Previously during Ironman distance events I had issues with hydration and fuelling resulting in a few subpar performances on the run. After speaking to a few other triathletes as well as my coach I decided to contact Gaby at IntensEATfit to get help in identifying and solving these issues to improve my overall performance. While working with Gaby we uncovered that I wasn’t fueling my training sessions well enough, I wasn’t practicing fueling through training enough to condition my stomach to take onboard the required amount of carbs and through testing that my fluid and salt loss was well above average. 

Gaby was great at explaining how these things impact my performance and it was a surprise to find out exactly how much carbohydrate and fluids it takes to successfully fuel and Ironman training & racing. Gaby instilled the importance in training nutrition, and we worked on my nutrition plan weekly allowing my body to get used to the amount of carbs it was taking on board, optimizing the plan to get the best result. This enabled one of the best training blocks I have completed and set me up for a great race in Cairns where I had a strong run to PB by over 10 mins on a challenging course.

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