How to Train Your Gut

Reading time: 3 min read
Prepare your digestive system to ingest more carbohydrates.
How to train your gut

If you are not completely new to the world of endurance sports and sports nutrition, you must have heard the phrase "train the gut" at some point or another.

What does it mean?

It is a concept that assumes that your digestive tract can get trained to handle sufficiently high amounts of foods and especially carbohydrates during exercise by improving digestion, tolerance, and potentially absorption.

This is especially important for endurance athletes because of their extremely high needs for energy (carbohydrates) during intense exercise.

Absorption versus tolerance

Before we delve into how to actually train your gut, we need to establish something important.

There is a difference between carbohydrate absorption and carbohydrate tolerance.

Tolerance is your body's ability to handle large amounts of carbohydrates without digestive issues. It's what makes people say: "I can intake even more than 120 grams of carbohydrates per hour without problems."

But then there's this other thing called absorption. Understanding the difference is really important. Absorption is the body's ability to actually absorb carbohydrates and use them as an energy source straight away or store them as glycogen.

For instance, a person can have a maximal absorption capacity for glucose at 60 grams per hour, but tolerate intakes in excess of 90 grams. This means that once exercise is stopped or the athlete stops consuming carbohydrates, there will be a considerable amount of carbohydrates left in the gastrointestinal tract.

What does this mean to you?

It means that even if you can intake 120 grams of carbs per hour without digestive issues, this doesn't mean your body will actually be able to use them as energy.

There's some good news and some bad news to this piece of information. The good news is that you can train your tolerance. The bad news is that there seems to be no objective way to measure and improve absorption. At least there is no solid evidence to demonstrate that absorption can be increased by training the gut.

So, what can you do about it?

Train tolerance and let your body do the rest.

Tolerance means how many carbohydrates you can ingest without digestive issues. Absorption means how many carbohydrates your body can actually use for energy. There is no objective way to improve absorption, but you can improve your tolerance.

How to train your gut

Training your gut is important. It's what allows you to sustain the extremely high energy intakes required by intense endurance exercise.

If your gut is not used to a high intake of carbohydrates, even peak physical condition might not be enough to perform in long events. You will either run out of energy, or digestive issues will slow you down.

Of course, following optimal fueling strategies goes a long way in sustaining a sufficient energy intake without digestive issues, but without training your gut, even these strategies might not be enough to prevent disaster.

So, how to train your gut?

Step 1 – Identify the problem

The first step is to identify what is actually causing you problems. Is your intake too high for your digestive system? Are you using wrong supplements? Maybe your whole diet needs a rework.

Often it's not easy to accurately identify the problem, but here are some steps you can take.

  • Reduce the amount of fiber in your everyday diet.
  • Remove FODMAP foods from your everyday diet.
  • Train without carbohydrates.
  • Change the supplements you use.

FODMAP foods

If you still experience digestive issues, the problem might be your gut. All you can do is train it.

Step 2 – Deal with the problem

Some problems are easy to solve, others are not.

Sometimes simply swapping to more efficient supplements does the trick, but you might experience digestive issues even if you don't intake any supplements during exercise.

Nduranz fueling products are designed to reduce digestive issues. The source of carbohydrates is a combination of glucose (maltodextrin) and fructose in the 1:0.8 ratio, which is optimal for best absorption. Our electrolyte mix is high on salt and low on magnesium, which is another common cause of digestive issues.

Once you know what is causing the issues, it's time to solve them.

Before exercise:

  1. Reduce fiber 1 to 3 days before exercise.
  2. Your meal before exercise should consist of little to no fiber, small amount of fats, and little protein. Focus on carbohydrates: 0.75-1 gram per kilogram of body mass for every hour before the start of the session (i.e., 1 g/kg if you have your meal 60 minutes before exercise)

Train the gut

This is a very popular strategy and involves getting the body used to tolerate more carbohydrates. 

How to approach training the gut? A few suggestions below:

  1. Perform exercise without additional food intake.
  2. Eat carbohydrates towards the end of the session. As you improve, increase the amount and eat carbohydrates sooner. For example, one energy gel 30 minutes before the end of your exercise. If all goes well, next time have one energy gel 60 minutes before the end of your exercise and one energy gel 30 minutes before the end.
  3. Slowly and patiently build up to your desired carbohydrate intake during exercise without digestive issues.
  4. Apply this strategy to more intense exercise. Exceed your target intake to build tolerance.
  5. Intake up to two Nrgy Units per hour even during short exercise of lower intensity.


Training your gut is important to sustain the high carbohydrate intakes required by intense exercise.

There is a difference between tolerance and absorption. The former is how many carbs you can intake without digestive issues, the latter how many you can actually use for energy.

There is no scientifically confirmed way to improve absorption, but you can build up your tolerance by training your gut.

Train your gut by following the steps above and slowly prepare your digestive system for higher intakes of carbohydrates.

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