For many runners, stomach pain is a nagging constant, and the culprit is often food. “Runners with GI distress don’t necessarily have weak stomachs. They’re just eating the wrong things in the wrong amounts and at the wrong times,” says Tara Dellolacono, an ultrarunner, registered dietitian, and nutritional strategist for Clif Bar.
Here’s the deal: Carbs are the body’s best fuel source while exercising. For most, sticking to simple carbs—the kind that are easy to digest and found in things like gels, goos, and candy—is the best way to avoid an upset stomach. But even when following that rule, your body can only absorb between 30 to 60 grams of the stuff per hour. “For newer folks, [the cause of their GI pain] is usually consuming too much at one time,” says Dellolacono. “They will start out empty and then slam a bunch of gels all at once to make up for it.”
The bottom line: Treating a weak stomach is a mix of picking the right foods and the right times to eat them. We’ve listed eight good things to eat, along with tips on how and when to eat them.
Weird colors, bizarre textures, and questionable tastes aside, gels are still your best bet when it comes to setting up your stomach for success. They’re easy to swallow, easy to digest, and used for energy almost immediately.
Don’t confuse the fact that gels can taste bad (and that therefore you don’t crave them) with their propensity to sabotage your stomach. “Cravings are tough,” says Matt Fitzgerald, nutritionist, coach, and author of The Endurance Diet. “Cravings have been found to be very crude. Really, you just want calories and carbohydrates.” Gels have been engineered to give the exercising body exactly that, with the least amount of resistance from the digestive system. The idea of eating a gel may make you want to gag, but the reality is that it’s your surest ticket to a pain-free stomach.
Just don’t consume more than three gels in an hour, or more than 60 grams of carbohydrates. Doing so will overload your system, which is often what gets runners into trouble.
If you’re constantly battling a knotty stomach, it might be best to consume primarily liquids while running. Electrolyte mixes like Tailwind, Skratch Labs, and GU Roctane have been specifically designed to fuel the body in motion in the most digestible form imaginable: liquid. “I’ve raced entire Ironmans on liquids,” says Fitzgerald, adding that in more than 30 years of racing, he’s never chewed while running.
Of course, hitting all of your nutritional requirements via electrolyte mix alone necessitates guzzling a lot of liquid. While Fitzgerald has found success with this method, he says most athletes will benefit from supplementing with gels. “I usually get all of my fluid needs from a carbohydrate drink, and then I make up the carbohydrate difference with gels.”
Performance gummies like Clif Shot Bloks or Honey Stinger Chews are loaded with the same perfectly calibrated ingredients as gels, just in a smaller, denser form. This is a good thing, says Dellolacono, because while a whole package has more calories than a gel, you can simply break the chews off one at a time and dole out fuel as needed. “You can add them seven grams [of carbohydrates] at a time over the course of your training, and test it out on yourself and see how high you can get without an upset stomach,” she says.
Bananas are a classic performance food for good reason. Most fruit is high in fructose, which in concentrated doses can upset the stomach. But bananas have only a moderate amount of the sugar, making them ideal for in-race fuel. However, they still have a decently high fiber content, which can throw a wrench into the digestive processes. One banana before a race or a bite or two at an aid station will likely be just fine.
This may strike you as counterintuitive: Potatoes are bulky, rich, and filling. In other words, the last thing you want while exercising. But in moderate doses—perhaps just a few bites or half a spud—and without the fatty toppings we usually associate with potatoes (butter, sour cream, bacon), boiled potatoes with the skin off and a bit of salt for electrolyte balance is the type of simple carbohydrate that will sit lightly in the stomach and be absorbed quickly.
When boiled or roasted, sweet potatoes have a creamy texture that make them easy to put down. But the reason sweet potatoes will play nicely with your stomach is simple: It’s a fast-digesting carbohydrate. Potatoes, both regular and sweet, do contain fiber, but a lot of that is in the skin. If you’re eating one during or just before a race, make sure to peel your potatoes first.
While definitely not as easy to eat as a boiled potato or gel, hard-baked snack pretzels are still a great option for those with a weak stomach. They’re a refined carbohydrate stripped of fiber and vitamins. That may strike you as a bad thing—“refined carbs” is practically a dirty phrase in the world of nutrition—but Fitzgerald is quick to point out that “a lot of people are fundamentally confused about the purpose of food in race nutrition. It’s not for your overall health—it’s to get you to the finish line.”
While you certainly don’t want to eat a lot of chips—they’re deep-fried, upping their fat content—they have a pleasant, starchy crunch with salt to stabilize your electrolyte balance. But Dellolacono says the primary benefit of something like a chip is simply giving the palate a break from the sugary, simple carbohydrates like gels. It’s not the best thing for the exercising body, but having something like a small chip will break up the monotony of sticky-sweet tastes and allow you to keep eating the stomach-friendly fuel afterward.
If you have a weak stomach, there’s good news: Both Fitzgerald and Dellolacono contend that just as you can train the body to run faster and longer, you can train the stomach to comfortably handle more food.
The best way to adapt the body to run with food is to train with a full stomach. There are a few ways to accomplish this: Drink a lot of fluid right before or during a run to make the stomach comfortable with increased volume, go on an easy run immediately after a meal, or simply practice eating while running. (Just like with training for distance, though, you want to slowly build up over time). You’ll never be able to increase how quickly you can absorb carbs—that remains constant, at about 30 to 60 grams per hour—but you can condition your body to be more comfortable with feeling full.
Dellolacono also points out that emerging evidence shows that the microbiome is sensitive to the foods you take in on daily basis. So if your daily diet consists of a lot of carbohydrates, your stomach will be better adept and digesting them while running. This also speaks to a point that Dellolacono maintains is the most important factor in developing a strong, resilient stomach: “It all comes back to a a foundationally fit diet,” she says. “Something I’ve learned while working with Clif athletes over time is that even though they eat whatever they want some of the time, I know they start with a foundationally fit diet that is really good for everybody. And then knowing they have that healthy gut to start with, they can train their guts to do more during activity.”