Nutrition for Ultra-Runners Part #5 – Gut Training

gut training

This is Part 6 of a 6 part series. 

Part 1 – Trending Diets in Ultra-Running

Part 2 – Pre-Workout and Pre-Race Nutrition for Ultra-Runners 

Part 3- Post-Workout and Recovery Nutrition for Ultra-Runners

Part 4 – Workout and Ultramarathon Nutrition

Part 5 – Everyday Nutrition for Ultra-Runners

Part 6 – Training the Gut for Ultra-Runners



Gut training is an often-overlooked strategy of ultra-running.  Unfortunately so, because the most common reason for a DNF is gastrointestinal issues.  These catastrophes could be avoided in many instances if the athlete had put an appropriate amount of time and effort into training their gut prior to race day.

It sucks to work your butt off in training for a race, logging hundreds and likely thousands of miles in preparation, only to have your race day ruined by stomach issues.  This blog will discuss how to train your gut properly to give yourself the best odds possible of avoiding GI distress during your next ultramarathon.  First, let’s go over some common mistakes ultra-runners make in training, which lead to inadequate gut training.

Common Training Mistakes – Gut Training For Ultra-Runners

#1. Not Fueling During Training Runs

If an ultra-runner doesn’t fuel during training runs, their gut will not be accustomed to taking in fuel. This leads to inadequate gut training and is a recipe for disaster come race day. Your gut CAN be “trained” in that it will slowly adapt to taking in more carbohydrates.

#2.  Too Little Fuel During Training Runs

If you plan to take in 300 kcal/hr during the race, don’t take in 200 kcal/hr during your long runs. That’s dumb. Take in fuel precisely as you plan to do so during the race.

#3.  Fueling With Different Fuel and Foods During Training

This one is pretty self-explanatory. Train your gut with the fuel and foods you are going to eat during the ultramarathon. You never know how you will handle a particular food or fuel until you’ve trained with it. Nothing new on ultramarathon day. Know what your food and fuel are well ahead of time.

Common Questions About Gut Training

What Type of Training Runs are Best for Gut Training?gut training

The best runs to train your gut are your long runs.  Long runs most closely resemble your race pace. The longer duration allows you to attempt to take in a certain amount of fuel consistently for hours at a time. You will not learn much from taking in 300 kcal/hr on a 1.5 hr run; it’s just not enough time.

Additionally, intensity affects digestion, and your race intensity will likely resemble long-run intensity more so than that of any of your other workouts.  If you have back-to-back long runs, use it to your advantage and train your gut on both runs.

How Often Should an Ultra-Runner Practice Gut Training?

Train your gut at least once per week, but preferably twice.

How Does an Ultra-Runner Train the Gut to  Handle More Fuel?

If you start at 200 kcal and don’t cause any stomach issues, bump it up to 225-250 kcal/hr for the next run and keep going in this pattern. Eventually, you will start to feel bloated. Train your gut at this amount for a few runs and see if the feeling diminishes. If it does, you can try to bump it up in small increments until you find your “sweet spot.”

In other words, the spot where your gut does not seem to be able to take in any more fuel regardless of training.  If 200 kcal doesn’t sit well, you may have to back it off to 150 kcal. Once that feels good, bump it back up and proceed as previously mentioned.

Your Sweet Spot

Most people aren’t going to be able to handle much more than 350-400 kcal/hr even with appropriate gut training. However, it makes sense to squeeze as much out of your gut as possible by training it appropriately. An additional 50 kcal/hr will amount to 1200 kcal in a 24-hour race!  That’s a lot of fuel and could dramatically change the outcome of your performance.

Once you find your sweet spot, there’s really no reason to attempt to push it further, as doing so will likely lead to negligible additional adaptation. Additionally, constantly pushing the limits of your fuel during your long runs can negatively impact your training sessions. Workout runs will obviously suffer if you’re consistently dealing with excessive fullness, bloating, or other GI issues.

Experiment with Various Foods and Fuels in Training

Things don’t always go as planned. Experiment with various fuels in case your primary fuel doesn’t sit well with you come ultramarathon day. I recommend experimenting with common aid station foods. Better yet, find out precisely what your particular race will have at their aid stations and experiment with that. This will help with gut training and help you determine which foods simply are not permissible come race day.

Summary of Gut Training for Ultra-Runners

Training your gut isn’t rocket science. Gut training is a reasonably simple addition to your training regimen that can have huge implications come ultramarathon day.  Remember that no matter how much you train your gut, GI issues can, and eventually will, still happen. They are and always will be part of ultra-running.

But that doesn’t mean you shouldn’t do as much as possible to prevent and reduce their negative impact.  Should you start to experience GI issues during an ultramarathon, remember that most FINISHERS in any given ultra WILL experience some gastrointestinal distress at some point during the race. In other words, it can be overcome.

For more information on how to overcome such issues, in addition to more ways to prevent them, check out 15 Best Ways to Prevent and Overcome GI Issues During an Ultramarathon.

Here are some key points to remember;

  • Train your gut during your long runs
  • Train your gut at least twice per week in the 2-3 months leading to an ultramarathon
  • If you don’t know what your gut can handle, start at 200 kcal/hr and adjust from there
  • Find your sweet spot and stick with it on race day
  • Use the same fuels you plan to use on race day to train your gut
  • Experiment with a variety of fuels and foods, this way, you have multiple options on race day

Know that gut issues can still happen, but you CAN overcome them.




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