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How To Train Your Gut For Ultramarathon Running

“Ultramarathons are eating contests with a little bit of food thrown in.” That statement by ultrarunning legend Ann Trason illustrates perfectly the importance of fueling during ultramarathon racing.

More often than not, however, this is an area many runners overlook when training for an ultramarathon. The result? Stomach cramps, bloating, nausea, and a resulting inability to fuel sufficiently for one’s chosen challenge.

And these issues are not trivial.

Gastric distress is one of the most commonly cited problems for endurance athletes and one of the top 2 reasons for non-finishes at ultramarathons.

So, how can you avoid your stomach going south, having a puke party, and not finishing your race because of fueling issues?

Simple. Gut training.

You need to train your gut just as you need to prepare your legs to withstand the rigors of running 50, 100, or more miles.

Why Gut Training Should Be A Part Of Your Ultrarunning Training Plan

If you never experience stomach pain, bloating, cramping, or the sudden need “to go” when you’re running, then you are one of the lucky few. For most of us, and ultrarunners especially, getting enough calories in during competition is challenging.

The good news, however, is that your gut is highly trainable.

And with a little bit of effort, planning, and experimentation, you may be able to improve your gut’s ability to tolerate large quantities of calories and carbohydrates during exercise.

And with an improved ability to fuel yourself during races, you will have better energy and possibly better race performances.

How To Train Your Gut For Endurance - The Basics

When you experience stomach issues during endurance exercise, you limit your potential. High energy outputs require high energy inputs, and if you fail to adequately hydrate and fuel, your performance will suffer. Regardless of how many hours you put in to train for the event.

The good news is that your gut is a trainable organ, just like your heart and lungs.

Sports nutrition scientist and triathlete Asker Jeukendrup points to contestants of eating competitions as examples. They train their stomachs to hold larger quantities of food with less discomfort than us, untrained individuals. Competitors do that by training their stomachs over several weeks.

As a result, the trained stomachs can hold more food, and the person experiences less discomfort with a full stomach.

A second aspect is your gut’s ability to absorb carbohydrates during exercise.

The current belief is that carbohydrate absorption is limited to a maximum of 60g – 90g / hour during training.

However, recent research shows that you can increase the ability of your gut to absorb carbohydrates during exercise.

You can achieve this by increasing the amount of carbohydrates you consume daily, primarily increasing your carbohydrate intake during your training runs. The type of carbohydrate you consume during your run matters, too. When you combine fructose and glucose, you can increase your carbohydrate absorption.

How To Train Your Gut For Endurance - Practical Guidelines

So how should you go about training your gut? First of all, you need to assess your baseline. We all have different eating and running habits, and you need to tailor your gut training to your needs.

For example, I have been an early morning runner since I started running in 2006. For many years I ran on water and coffee only (I don’t recommend it). I needed to start slowly introducing calories on my runs. Once I could stomach honey without issues, I began incorporating solid foods, like fruit bars and dried dates.

On the other hand, suppose you are already eating a gel for every 40 minutes that you run. In that case, you might simply need to start increasing your calorie intake during key training sessions. 

So, assess how many calories you are consuming at the moment and what you would like to improve. Then you have two main areas you can train: 

  1. You can train yourself to run with solid foods more easily
  2. You can train yourself to absorb more carbohydrates per hour

Let’s look at each strategy in turn

1. Train Yourself To Run With Food In Your Stomach

If you want to learn how to run more comfortably with food in your stomach, you could start to have a small snack right before your run, run after a full meal, and practice eating “real foods” during your runs.

Again, start slow and improve over time. Suppose your current routine is to jump out of bed, drown an espresso and head out the door. In that case, you shouldn’t jump into eating 2 burgers immediately before your training runs.

You wouldn’t jump into 100 mile training weeks after a 6 – month running break, would you?

Experiment with different types of foods. Dried fruit works well for many people. Others like boiled potatoes, bananas, and sandwiches. Rice crackers, energy balls, or energy bars are also good options.

Make sure to test out savory options to have some variety during the later stages of an ultra-marathon. Many people experience “flavor fatigue” and don’t want sweet food anymore after several hours of running.

2. Train Yourself To Absorb More Carbohydrates While Running

The easiest way to become better at absorbing more carbohydrates during exercise is to increase your daily carbohydrate intake – mainly during your runs. Research shows that this increases the absorption and oxidation of ingested carbohydrates.

I couldn’t find much research on this practice, but Jeukendrup recommends ncreasing your carbohydrates during exercise sessions at least once a week for 5-10 weeks.

Every once in a while, practice taking in more carbohydrates than the recommended 60-90g / hour and experiment with different options.

Some people do well using only gels, others not so much. I love honey and maple syrup and will supplement with drink mixes from precision hydration if I want to bump up my calorie intake.

When Should You Train Your Gut?

Just like you wouldn’t try to simulate race day trail conditions on every single training run, you don’t need to train your gut for race day conditions on every training run.

The best time to do so is doing key training sessions.

That means once a week or every other week is perfectly fine. Interestingly you also might not need to gut train throughout the entire year, as it seems that adaptations happen pretty quickly.

However, suppose you have a very sensitive digestive tract, like me. In that case, you might want to take a longer-term approach and keep your carbohydrate intake consistently high throughout your key training sessions. I find that my tummy is happier when I don’t have huge swings in carbohydrate and fluid intakes over several months.

Suppose your gut is not as sensitive, and you adapt quickly without much trouble to higher food intakes. In that case, all you might need are 8 weeks before your race, where you practice your nutrition strategy during your key training sessions.

To Summarize

Your gut is a trainable organ, and you should treat it as such. Practice fueling during your key training sessions and experiment until you find foods that you can consume on your run without much hassle.

If you gradually improve your body’s ability to digest and use carbohydrates during exercise, you will be better fueled during races. And you’ll likely enhance your race experience and results.

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