Cyclists can be odd ducks, but one place where they have really nailed it is in mid-activity fueling. Yeah, they may start with gels and energy bars. Then they’ll wash that down with burritos, pastries, and calzones. Cyclists are often powerful machines that turn junk food into watts.
Here’s the cool part. Athletes I have coached coming from serious backgrounds in cycling or cross-country skiing usually have iron stomachs in running too, even with all the up-and-down movement. That’s weird, right? What are we seeing? There are a few potential causes:
Option 1: Top-level cycling and skiing are basically competitive eating activities, so those athletes are chosen for their strong guts early on.
Option 2: They train their stomachs so thoroughly in those sports that the adaptations last long-term. They are all about that pizza life, so their stomachs catch up.
Option 3: I need to stop noticing patterns from small sample sizes.
Based on the physiology and research on gut training, I really think it’s Option 2 (sprinkled with just enough Option 3 to add some spicy flavor). Those cyclists and skiers eat proficiently during activity because they have ample practice. They are constantly faced with the big decision: eat a mid-ride calzone, or possibly not make it home. Choose calzone enough, and a stomach can handle almost anything you throw at it.
Now for the premise of the article. What can a runner that has stomach troubles learn from those athletes, plus the research? I’m not talking about people with occasionally sensitive GI tracts. Instead, I’m talking about the athletes that consider Imodium as important as running shoes, who throw up with the passion and velocity of the demongirl from the Exorcist. For crappy guts, are there options to feel better and escape the bile lifestyle?
“Simply put, yes,” says nutritionist Kylee Van Horn of Fly Nutrition, who works with many athletes I coach on these issues (ideally contact a nutritionist like Van Horn for these and all other issues related to fueling). “If you practice a plan that applies nutrition science based on your needs and history, you can work through many gut issues.”
Van Horn says that the big takeaway is that your stomach is likely highly trainable, even if you have an unhappy gut history, but working from a genetic baseline, and incorporating things like food sensitivities specific to your background. She wrote an article on the topic here.
Optimizing your genetic digestive potential requires practice. Get your calzone recipes ready and let’s dive in.
The Gut Training Basics
Gut training consists of multiple pathways, some of which are understood well, and others that are a bit more murky and individual-dependent. Basically, it’s hard to measure the stomach directly without cutting a subject open. So we may not be isolating the specific variable at issue (at least for unopenable human subjects), even though we know the general approach is effective.
Increased toleration: A 2017 review article in the journal Sports Medicine highlighted the example of competitive eater training, where hot-dog-based organisms will consume a large amount of fluids to train their stomachs to tolerate more volume. The authors say that there may be some expansion of the stomach involved, along with changed perceptions of fullness/bloating. A 2008 study in the journal Physiology and Biochemistry similarly found increased stomach comfort with consuming a large amount of fluids after just over a week of practice.
Accelerated gastric emptying: The 2017 review article examined a few studies that found that meals with certain types of nutrients could increase the rate of gastric emptying of those nutrients, reducing the time it took for food to escape the stomach and make it into the safer confines of the intestine. That should increase absorption rates and reduce stomach upset as well.
Increasing Transporter Number and Activity: We don’t need to get deep into the weeds here, but the basic gist is that researchers theorize that consuming nutrients upregulates mechanisms used to process those nutrients. For our purposes, do it more, and you should get better at it. That’s also what my dance teacher said, but based on the looks I get at weddings, I’m not buying it.
A fun area of related theory is based on responses to repeated exposure to nutrients in the digestive tract. There is some evidence that cells in the digestive tract can alter function based on environment, and possibly even that those changes are heritable to new generations of cells (especially important due to rapid turnover of many cells in the GI tract). It could apply to everything from microbiota to cells in the intestinal wall, though this is not settled science.
Gut Training Studies
Tons of studies show gut training in action, which is all that really matters if you think you’re doomed to a combustible gut. A 2017 study in Applied Physiology, Nutrition, and Metabolism found that just two weeks of gut training improved GI symptoms and running performance. A study that came out just last week in the Journal of Strength and Conditioning Research found that more frequent ingestion of gels increased performance over less frequent gel ingestion. The 2017 review study cited numerous examples of gut training in action. Those researchers recommended up to 90 grams of mixed-source carbohydrates per hour in activities over two hours to optimize gut training outcomes and performance.
“Make sure you gradually introduce changes,” Van Horn says. “In my clients, we have the most success tailoring plans specifically based on individual background and goals, rather than applying uniform formulas.”
How To Use Gut Training
Gut training works. But how can you get it to work for you? Here is where the art comes in, and you can find the approach you like, ideally working with a nutritionist.
I have seen a four-point template protocol work for athletes with various backgrounds, based on some recommendations from Van Horn. First, fuel many of your long runs as you will fuel on race day (though you don’t need to do it on every single long run). Second, hydrate adequately for your needs on every run you can. Third, fuel slightly more than usual once or twice on a long run to get increased comfort with it. Fourth, mix up food sources so you aren’t overly reliant on one thing.
This article is not for those types of solid-stomach athletes, though. This article is for the athletes with GI tracts that are as effective as the U.S. Senate and eager to undertake explosive Brexits.
There is hope! I suggest five steps for those athletes with a crappy stomach that take the recommendations above a bit further. These suggestions are based on some athletes that have reversed their extreme stomach woes, but a different approach may work for you. Things like pre-run fuel, heat tolerance, gut microbiota, food allergies, and specific food source are beyond the scope of this article, which is already long enough to be written by George R.R. Martin. Always talk to a nutritionist/doctor before making any substantial changes or if worried about health.
Fuel on almost every run, starting with a gel or similar, progressing to more complex foods that sound fun
Constant reinforcement of fueling can help the digestive tract adapt, harnessing whatever environment-based adaptations might be achievable for your background and genetics. Plus, it will take away any psychological stigma.
Find what works for you, which varies a ton based on the person. My wife/co-coach Megan and I run for Spring Energy and recommend it to athletes we coach because it has good ingredients, absorbs well, and is delicious. Whatever fuel you choose, just make sure you try different approaches if what you’re doing is not working. After you get comfortable with gels, you can move onto more complex foods.
Fuel on most long runs like you will in the race itself
Use longer runs as fueling practice. I usually recommend a gel or similar at 45 minutes and every 20-30 minutes after, aiming for around 200-300 calories per hour, adjusting based on your background. That will capture the gut training benefits of most protocols in the research.
Spring Energy (relationship noted) and other companies now make higher-calorie gels that are a good option to increase the stimulus. Make sure you’re hydrating as close to race day needs as possible too, particularly in longer runs. It’s highly variable, but 16 ounces of fluid per hour is a good place to start, adjusting up or down based on weather and sweat rate, making sure sodium stays balanced too. In a perfect world, the fluid has some calories and electrolytes, which helps absorption rates and sodium balance.
Fuel slightly more than usual on runs a few times, including some shorter runs
Toleration is a key part of gut training, and one way to do that is to take in more than you will on race day. You can use higher-calorie gels, or even fun foods like breakfast burritos. I have had a couple athletes take a page out of the cyclist playbook and stop at a coffee shop mid-run for a big pastry.
Periodically, drink your hourly fluids at once, rather than spread out in small sips, being careful not to exceed your hydration needs
Now we’re going to the competitive eater example. While it’s important to never overhydrate, which could have dangerous side effects, you can practice filling up the stomach by drinking your hourly fluid at once. What I like athletes to do is go to a water fountain at the tail end of their run when they need to hydrate anyway. Anecdotally, some athletes have said this is the most important thing for them to practice to gain comfort.
On race week, take your race-day fuel on the last couple runs, even short ones
The research indicates that gut training benefits can accrue on very short cycles, so use race week to practice with whatever you will be using on race day. Whether those short-term adaptations are due to cellular-level changes or something in how the brain sends signals to the digestive tract, there’s almost no downside.
You don’t need to follow this specific protocol. Find what works for you, partnering with a nutritionist if you can. No matter what you do, don’t lose hope. If the problem stems from your GI system and how it processes fuel, that can adapt over time. If it’s related to something else like a food allergy or health issue, nutrition experts and doctors can help you find answers.
You might never train yourself into having an iron stomach. But you can probably train yourself into having a wood stomach.
Yeah, like the old wood cities, it might all burn down every once in a while. But it’s solid and reliable most of the time. And if you have ever dealt with a crappy gut, solid and reliable most of the time is pretty darn awesome compared to the alternative.
David Roche partners with runners of all abilities through his coaching service, Some Work, All Play. His book, The Happy Runner, is about moving toward unconditional self-acceptance in a running life, and it’s available now on Amazon.