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5 Types of Food to Never Eat Before a Run (And What to Eat Instead)

You know that some foods are better than others pre-run, but do you know what they are?

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There are some foods that just aren’t worth the risk before a run—they’re bound to give you stomach distress or make your run harder. It’s important to understand why eating particular things make you feel lousier than others. But it’s equally crucial to know what you should eat instead, so we’ve provided just-as-delicious swaps for the following foods that are best to avoid pre-run.

Skip: Fried or greasy foods

Stay far away from anything fried or greasy before a run. Delicious though they may be, they take much longer to digest due to the high fat content. Therefore, you may feel as if it’s just sitting in your stomach as you run. It’s best to save the salty cheese fries, or even that greasy breakfast sandwich, for after the running is done.

Eat this instead: Healthy fats

When it comes to healthy fats, you have a little more wiggle room, according to Molly Kimball, RD, CSSD, registered dietitian with Ochsner Fitness Center in New Orleans. “Just know what your limits are,” she says, noting that even the healthiest of fats are still broken down and digested slower than other macros, which can lead to gastrointestinal issues like cramping on the run. The key: When eaten in moderation, that slower digestion can actually be a good thing, especially for a longer run. “Healthy fat can provide a more sustained release of energy,” Kimball explains. “Most people would be OK with a quarter avocado, an egg, or one or two tablespoons of nut butter before a run.”

Skip: High-fiber foods

Carbs are key for energy, but too much fiber can stress out your GI tract. “Some of these really high-fiber cereals, like All-Bran and Fiber One, have 14 grams of fiber in a half-cup,” says Kimball. “To digest that fiber, any of the water in your belly is going to bind to it and help swell it up just like you would see it in your bowl. So if you eat that for breakfast it’s going to be expanding in your stomach during your run and you can experience cramping, gas, and bloating.”

Eat this instead: Oats

Oats (as in, oatmeal) are more moderate in fiber (at 4 grams per ½ cup) and will be tolerable pre-run for most people, per Kimball. Whole-wheat bread would also be a good substitute. Both options still provide a nice amount of carbs to help fuel your miles.

Skip: Refined sugars

According to the Journal of Science and Medicine in Sports, research found that athletes performed significantly faster 45 minutes after eating a low-GI (glycemic index) meal rather than a high-GI meal. In other words, a low-GI meal would be something simple with minimal sugar, like an apple with peanut butter. High-GI foods include white bread, high-sugar energy bars, and ice cream. Consuming these before a run may cause you to become fatigued more quickly. “Especially if it’s before a shorter run, you don’t really need sugar,” says Kimball. “The only time that I recommend runners eat higher glycemic, or higher sugar, foods is when they’re fueling mid-run.”

Eat this instead: Natural sugars

The apple the athletes in the study consumed would work great as a pre-run snack carb source, as would oatmeal, some whole-wheat bread, or berries.

Skip: Protein bars

Often, these are high in sugar alcohols which—you guessed it!—can cause GI upset, like gas, diarrhea, and bloating. “Sugar alcohol in the form of maltitol or sorbitol are some of the most common ones that I see in protein bars,” says Kimball. “They truly have a laxative effect. I would not want you to eat those before your run.”

Eat this instead: Whole food–based snack bars

Go for something else portable and easy, like a Dark Chocolate Nuts & Sea Salt KIND bar or an Rx Bar that is made with dates and egg whites. Here’s a list of dietitian-approved bars for morning, noon, and night.

Skip: Pungent foods

Some spicy foods help to speed up your metabolism; however, too much of it can lead to heartburn and indigestion. It’s best to save this for after the miles are over. But the same can be true for other more surprising foods that leave you belching up the flavor of that food. Kimball cites cabbage, garlic, onions, and cauliflower as examples. “You may love that cauliflower crust pizza, but if you ate it for lunch, and you’re doing an afternoon or evening run, you might be belching cauliflower the whole time,” she says. “It’s not going to upset your stomach, but tasting it your whole run won’t be pleasant.”

RELATED: Understanding Food Intolerances for Better Performance

Eat this instead: Simple snack

Save the spicy, bolder flavors for post-run and go for a simple homemade “pizza” with grilled tomatoes and a little cheese on whole-grain bread beforehand.

Monitor: Lactose

Lactose can be difficult for the stomach to digest. Gastrointestinal specialist Mervyn Danilewitz explains that the elimination of dairy 24 hours before running is the cure for a number of runners’ stomach problems. And according to Today.com, at least 60 percent of runners experience varying degrees of nausea and unpleasant stomach issues when they run, due to the effects of dairy. However, if you’re in the 40 percent that doesn’t typically have those adverse symptoms during exercise, you’re in the clear to keep dairy in your pre-run rotation, according to Kimball. “If you’re having GI issues, and you consume lactose before your run, then do an experiment and see if eliminating it helps. If you’re having lactose before a run—say some milk in your coffee or a Greek yogurt—and you don’t have GI issues, then I wouldn’t have any problem with that.”

The bottom line: Do some food experiments

“Everyone is different in their level of GI function and sensitivity,” Kimball says. “It also depends on how regular you are and when you go to the bathroom.” For a runner that has a bowel movement first thing in the morning like clockwork, she probably doesn’t need to worry about what she eats the night before her run. However, a runner on a less predictable schedule might be pulling over for a mid-run pitstop if they ate a little broccoli the night before their a.m. miles. “During your training run, that’s your test time,” Kimball says. “Nothing new of any type on race day or when it really matters.”