The stomach is a trainable organ. Just as run training helps strengthen your legs and make your cardiovascular system more efficient, nutrition training helps improve your stomach’s ability to handle the large amount of calories you need to consume during longer runs and races.
Failing to train the stomach as hard as you train your legs, lungs and heart could ruin your race no matter how many miles you run.
Asker Jeukendrup, a leading exercise physiologist and sports nutritionist, illustrates the principle of gut training simply in a 2017 review article in the journal Sports Medicine: with hot-dog eating contests. In July 2017, the Kilian Jornet of competitive eating, Joey Chestnut, ate 72 hot dogs and buns in 10 minutes. He accomplished this feat of staggering gluttony through a complex training regimen focused on expanding stomach volume and decreasing perception of fullness. Similarly, trail runners can train their stomachs to maximize absorption and decrease GI distress during activity. And unlike Chestnut, you don’t have to dip hot dogs in water to do it.
A 2017 study in the journal Applied Physiology, Nutrition, and Metabolism showed the effectiveness of a short bout of gut training. The study took 25 endurance runners through an initial “gut-challenge trial” (a term that is essentially a synonym for “ultramarathon”). The gut-challenge trial involved low-level aerobic exercise for two hours (at 60 percent of VO2 max) and a one-hour distance test, all while consuming the equivalent of about a gel packet every 20 minutes.
After the initial gut-challenge trial, the 25 runners were separated into three groups. For two weeks, two of the groups practiced consuming carbohydrates during exercise, and one placebo group ran without consuming carbohydrates. The gut-challenge trial was then repeated, and the results were staggering. Two weeks of gut training improved performance and reduced symptoms of gastro-intestinal distress for the carbohydrate groups. Meanwhile, the placebo group got slower and crampier.
How can you harness the power of gut training?
1. Practice your race-fueling strategy consistently during runs over 90 minutes.
When it comes to fueling, there’s nothing to it but to do it. Develop a fueling and hydration plan for your next race, practice it on most of your long runs and then use that same plan on race day.
In the Sports Medicine review article, Jeukendrup breaks down the current state of knowledge about gut training. Among other things, stomach comfort improves with practice ingesting large amounts of fluid; and absorption of carbohydrates improves with practice ingesting carbohydrates during training. Just like hot-dog eating, free-throw shooting and guitar shredding, practice might not make perfect, but it does make better.
The general rule is to start at 200 to 300 calories per hour and adjust as needed for your body type, goals and background. In practice, I usually have athletes start with a gel every 30 minutes (with the first gel waiting until one hour in), supplemented by diluted sports drink to add calories and hydration. But a wide range of strategies can work—develop your plan and stick with it.
2. Run with different types of fuel.
A race-day diet of gels can work for some, but especially in longer ultras, another packet of sweet goop can become nauseating. Within the same calorie-per-hour framework, you can add other foods, including foods that are not just carbohydrates.
Notably in the Applied Physiology study, one carbohydrate group consumed solid food, as opposed to solely gels. That group had most of the same positive adaptations, demonstrating that foregoing gels does not necessarily mean foregoing performance.
I sometimes have athletes eat their favorite snack during long runs to see how far we can push their stomachs, especially before ultras. Some of my favorites are salt and vinegar potato chips, Reese’s peanut butter cups and bacon-rice balls.
If you plan on consuming other foods, practice with those in training too. Just like run training, start by practicing extreme moderation before progressing to more advanced foods (mid-run pizza, anyone?).
3. Consider liquid fueling strategies.
For some runners, real food and even gels may cause GI distress. For these runners, liquid fueling can work, including in all-day 100 milers (for example, Magda Boulet fueled with Roctane drink when she won Western States in 2015).
A 2016 study in the International Journal of Sport Nutrition and Exercise Metabolism had nine athletes complete a five-hour simulated triathlon two different times—once fueling with gels and once fueling with liquid nutrition. While performance was not significantly different, seven out of nine reported GI discomfort with gels and none reported discomfort with liquid.
Have a finicky stomach? Try liquid fueling, aiming for the calorie-per-hour total that works for you. This method requires some advanced planning, so make sure you don’t just wing it on race day and end up under-fueling and bonking or over-fueling and bloating.
David Roche runs for HOKA One One and NATHAN, and works with runners of all abilities through his coaching service, Some Work, All Play.