Female Cyclists Athlete In Helmet In Glasses Looking At A Nutrition Bar During Gut Training

How to Train Your Gut for High Carbohydrate Intake

BY Lisa Nijbroek

If you struggle to tolerate high carb consumption, don’t fret – your gut is highly trainable. Here’s how to train your gut for optimal fueling on race day.

Endurance races often require a high hourly carbohydrate intake. Trained amateurs and professional cyclists alike aim for as much as 120 grams of carbs per hour. But doing this takes practice. You can’t just jump into race day and expect your body to efficiently consume such a high amount of carbs if you’ve never done it before. 

Your body’s ability to utilize and absorb large amounts of carbs requires gut training. If you don’t train your gut, you’re likely to run into gastrointestinal problems on race day, one of the most common reasons for a DNF (did not finish) result among endurance athletes. 

But like the muscles in your body, your gut and digestive system are highly trainable. Here is how to train your gut so stomach issues don’t stand a chance on race day.

Gut Training Takes Time

Optimal gut training might take several weeks, depending on how ‘’trained’’ your gut system is when you start. If you’re inexperienced in consuming food and fluids during exercise, starting your gut training 6-10 weeks before race day is best. 

To begin gut training, you need to ask yourself a few questions:

  • How many carbs per hour do I need for this race? 
  • What time does my race start? When will I eat breakfast? 
  • What temperature is expected for my race? How much will I need to hydrate?

These considerations are key to your overall nutrition plan and will guide your gut training process.

Pro Tip: Use Tech to Your Advantage

Several online applications (like EatMyRide) can assist your gut training by allowing you to simulate and practice your race day fueling and hydration strategy on the bike. Such applications help you gain insights into your current carbohydrate intake, and from there you can begin gradually building up.

1. Practice Weekly “Gut Training” Days

Dedicate one day a week as a “gut training day” where you practice race-day nutrition during your training session. Start building up from your comfortable starting level. For example, if your goal is to build up to 90 g/hour, you might have to start at 30 g/hour.

Perform a minimum of one training session with an amount that feels comfortable before building up. Aim for small steps, such as an increase of 10 g/hour the next week. You might also consider doing some training with slightly higher intakes than you’ll aim for during your race. 

Tip: When ingesting more than 60 g/hour, consider combining multiple transportable carbohydrates (glucose and fructose) in a 2:1 or 1:0.8 ratio. 

What Form of Carbs Is Best?

Depending on the duration, intensity, and parcours of your race, you can use liquid carbs in the form of gels and drinks, solid food, or a combination. Many people find eating solid foods combined with sports drinks at the beginning of the race is usually easier. Gels are often used in the last part of a race, as they’re easy to swallow and don’t require chewing. But keep in mind that strategies vary from person to person, which is why you need to train and gain trust in your individualized fueling strategy. 

Also, remember that not all bars and gels are the same. The amount of carbs actually varies quite a bit among brands. Often during long endurance events, you’ll come across stations at the side of the road offering different nutrition bars you can take for free. While that sounds very attractive, it’s best not to try something new on race day. 

2. Plan Your Pre-Race Meal

Plan what you’ll eat as the last meal before your race, and check whether it’s available if you stay in a hotel overnight. Aim for a minimum of 1g carbohydrates/kg body weight (up to 3-4 g/kg body weight) before extreme endurance events. For example, an 80kg cyclist should consume a minimum of 80g of carbohydrates as a last meal. This might look like a bowl of oatmeal made of 60g oats and 250 ml semi-skimmed milk, along with one portion of fruit with some honey on top. 

Although it depends on the individual, it’s usually best to consume your final pre-race meal roughly 2-3 hours beforehand. 

Some athletes find it difficult to eat before a race, especially when the race starts early in the morning. If you’re one of those people, you might consider getting your carb intake from drinks (like a smoothie). It helps to start training your race-day breakfast in the weeks before your race. Additionally, be aware of your fiber, fat, and protein intake. It’s wise to skip products like avocado, nuts, and big portions of savory foods like salmon/chicken due to high amounts of fats and/or protein that might lead to gastrointestinal issues. 

To reduce the risk of bloating while improving your capacity to absorb carbohydrates, you might try eating a meal close before the start of your training. If you’re going to do this, start with training sessions that aren’t too intense at first. 

3. Find Your Personal Sweat Rate & Hydration Needs

Knowing your personal sweat rate in different circumstances helps determine exactly how much you need to hydrate during your race. Sweat loss is highly dependent on several factors: temperature, humidity, intensity, acclimatization, and even genetics all play a role.

When finding your sweat rate, it’s best to do so during training sessions between one and two hours. If you go any longer, glycogen loss can influence the accuracy of your measurements. Perform multiple sessions based on different scenarios to get an idea of what to expect on race day.  

Once you know your sweat rate for your expected race day conditions, you can determine how much weight loss is acceptable at the finish line. Ideally, aim for around 2% total body weight loss. For example, if your start weight is 80 kg, your safe body weight loss of 2% at the finish line would be 78.4 kg. 

An additional 0.5 kg extra weight loss is acceptable for ultra-long endurance events that last more than four hours. This is because that extra weight loss is likely from fuel depletion. Every gram of glycogen saved in your muscle and liver binds with some fluids, which explains why you’re sometimes a bit heavier after consuming high amounts of carbs.

Determining Hourly Hydration

After calculating how much weight you can expect to lose at the finish line, you’re then able to determine exactly how much you need to hydrate during the race. This is done in three steps:

  • Step 1. Multiply your expected race time by your sweat rate
  • Step 2. Subtract your acceptable weight loss of around 2%
  • Step 3. Divide this number by the total time of the race to get your hourly intake. 

Example: An 80 kg cyclist has an expected sweat rate of around 1.4 liters per hour during a mid-summer race. An acceptable weight loss for this athlete is 2% of 80 kg, meaning 1.6 kg. Plus approximately 0.5 kg extra for fuel loss is 2.1 kg. The athlete is performing a 4-hour race.
4 hours x 1.4 liters = total expected sweat loss of 5.6 liters
5.6 liters – acceptable weight loss of 2.1 kg = 3.5 liters left to consume total.
A race of 4 hours, meaning 3.5 liters / 4 hours = aiming to drink almost 900 ml/hour

How to Find Hourly Hydration Intake

Drinking according to your total losses often requires you to drink much more than you think. Choose mostly isotonic drinks (like 6D isotonic drink) in combination with water during warm weather situations. During cold weather circumstances, consider variating with a hypertonic drink (meaning it has a higher number of solutes than in human blood, for example 6D energy drink). 

Lastly, listen to your body and digestive system. If you feel bloated in a race and fluids are not emptying from your stomach, reduce the intensity temporarily where possible. And don’t forget to make sure you start your race well-hydrated (a light pale yellow color of your urine).

Take Home Messages

Like any other system in your body, training your gut takes time. It might take several weeks and feel a little uncomfortable at first, but this is normal as your gut system adapts. Remember these key takeaways before you start your gut training journey: 

1. Begin with the end in mind. Design a nutrition and hydration plan for your race day 6-10 weeks in advance.
2. Take one ‘’gut training’’ day a week that simulates race situations.
3. Plan and practice what you’ll eat as your last big meal before your race.
4. Find your personal sweat rate to determine hydration needs.

Gut training makes you feel less bloated, increases gastric emptying, increases your capacity to absorb carbohydrates, and ultimately helps you race to the best of your ability. The EatMyRide app can help by displaying your carbohydrate expenditure and intake needs for each workout. It also allows you to create detailed nutrition plans before, during, and after each workout and race. EatMyRide now syncs directly with TrainingPeaks.


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Hoffman, M., & Fogard, K. (2011, March). Factors related to successful completion of a 161-km ultramarathon. Retrieved from https://pubmed.ncbi.nlm.nih.gov/21487147/

Jeukendrup, A. (2017). Training the gut for athletes. Retrieved from https://www.gssiweb.org/docs/default-source/sse-docs/jeukendrup_sse_178.pdf?sfvrsn=2

McCubbin AJ. (2022, June 13). Modelling sodium requirements of athletes across a variety of exercise scenarios – Identifying when to test and target, or season to taste. Retrieved from https://pubmed.ncbi.nlm.nih.gov/35616504/

Viribay, A., et al. (2020, May 11). Effects of 120 g/h of Carbohydrates Intake during a Mountain Marathon on Exercise-Induced Muscle Damage in Elite Runners. Retrieved from https://pubmed.ncbi.nlm.nih.gov/32403259/

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EatMyRide tracks your carbohydrate burn and intake in real time so you know exactly when and how to fuel. It also helps you perfect your fueling strategy based on your personal metabolic profile. EatMyRide now integrates with TrainingPeaks.

Lisa Nijbroek
About Lisa Nijbroek

Lisa Nijbroek is a sports nutritionist and human movement scientist with more than eight years of experience in World Tour cycling. She has a master’s degree in Human Movement Sciences, a bachelor’s degree in Nutrition and Dietetics, and a post-bachelor degree in Sports Nutrition. Lisa is also the scientist for EatMyRide, the first DIY nutrition app tailored to optimize performance during workouts. EatMyRide syncs directly with TrainingPeaks and shows carbohydrate, fluid, and sodium needs during each TrainingPeaks workout.

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