The 6 Worst Things You Can Eat or Drink Before a Workout

Whether you’re pounding the pavement outside or pumping weights at the gym, one thing stays constant: Your body needs the proper fuel to perform.

Maybe your goal is to build muscle. Or maybe you’re aiming to increase your mileage. Either way, what you choose to eat and drink pre-workout can propel you to success—but the wrong choices can hinder your progress.

So before you head out to your next workout, pay close attention to what you’ve been putting on your plate in the hours leading up to it. These six diet blunders can do damage, whatever your goal. (Want to try a workout you can do right at home? Try The 21-Day MetaShred from Men’s Health—you’ll build lean muscle and burn off the fat covering it.)

SKIP BEFORE YOUR WORKOUT: CARBONATED DRINKS

Drinks like seltzers and sodas are infused with carbon dioxide, which creates carbonation. Those bubbles can make people feel gassy and full, or cause abdominal pain, says Pamela Hinton, Ph.D., director of nutritional sciences graduate studies at the University of Missouri. Most of the carbonation escapes through your mouth, but some should still make it to your stomach, causing short-lived bloating and gas. It should pass within an hour, she says.

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Certain discomfort is good, like if you feel the burn completing your last couple reps or finishing a sprint. But you need a basic level of physical comfort to be able to push yourself at all. If carbonated drinks make you feel bloated or crampy during your bike ride, lift session, or run, it can keep you from reaching your full potential.

Instead, twist open a bottle of plain water to hydrate. “You really only need a sugar-containing sports drink if you’re exercising long enough to deplete your carbohydrate stores,” Hinton explains. If you’re exercising for 90 minutes or longer at moderately high intensity, you can reach for a sports drink: In those cases, your body can immediately use those simple carbs from sugar for energy.

SKIP BEFORE YOUR WORKOUT: FIBER-RICH FOODS

Yes, that black bean vegetable soup is a great choice for lunch—the fiber fills you up, so you’re not hungry an hour later.

But while fiber is great for your gut, it can hinder your workout. High-fiber foods—like broccoli, high-fiber cereals, or lentils and other legumes—take longer to digest and draw blood to your digestive system.

“Then you have a lot of blood flowing to your gastrointestinal tract when you want it to be flowing to your muscles,” Hinton says. This means your muscles aren’t getting the oxygen, sugar, and amino acids—all delivered by the blood—that they need during a workout.

With about 15 grams of fiber per cup, black beans can also lead to gastrointestinal distress while running, when there’s more jostling of your stomach. That can make you feel queasy and bloated, give you cramps, make you fart, and cause unwanted bathroom breaks.

“If you have to stop to go to the bathroom or your stomach is in pain, that’s going to hinder your performance,” says Veronica Mullins, M.S., R.D., an assistant professor of sports nutrition at the University of Arizona.

Men ages 50 and younger should get about 38 grams of fiber per day, so don’t skimp on the macronutrient throughout the whole day—but do limit your intake of high-fiber foods for a few hours before working out, Mullins says.

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SKIP BEFORE YOUR WORKOUT: LOW-CARB, HIGH-FIBER PROTEIN BARS

Carbohydrates are your body’s preferred energy source. Your body converts carbs into sugars, which then get absorbed into your bloodstream, travel into the cells in your body, and can be used for energy.

“A lot of strength athletes think they don’t need carbohydrates, but they do,” Mullins says. “Our muscles, our brains, they function primarily on carbohydrates.”

If you go low-carb, your body will break down muscle proteins for energy, which can prevent muscle growth. “During anaerobic activity, carbohydrates are the only source of energy,” Mullins adds. “Without carbohydrates, there will not be enough energy for a hard workout.”

So if you need a snack before your workout, try a low-fiber bar with anywhere from three to five times as many grams of carbs as protein—say, 15 to 25 grams of carbs and 5 grams of protein—within the hour, suggests Mullins. (Those high-fiber bars can spark GI distress.)

The protein in the bar is important too, since it promotes muscle maintenance and growth, and protects against muscle breakdown.

“If an athlete does not consume enough protein, the body will break down muscle tissue, leading to overall protein loss and a decrease in performance,” she says.

SKIP BEFORE YOUR WORKOUT: NUTS

“Everyone thinks nuts are this super-food, but they’re mostly just fat,” Hinton says. And fat, like fiber, travels more slowly through your body. That means more blood flow to your GI tract and liver when you are trying to digest fat-heavy foods.

Nuts, cheese, and avocados contain protein, which is good, but their high fat content makes them pre-workout no-nos.

“You don’t want to eat something high in fat, like fast foods, fried foods, or cheesy foods,” she adds. Avoid them six to eight hours before your workout.

SKIP BEFORE YOUR WORKOUT: WHOLE GRAIN TOAST

Complex carbs—like those in whole grains, vegetables, and beans—won’t help you fulfill your potential during endurance training.

“Endurance athletes are going to be better off with simple carbohydrates,” Mullins says, which your body can absorb more rapidly for immediate use.

That’s one case where you might want to go with the plain white toast: It’s primarily made up of simple carbs and will supply your body with readily available energy.

Plus, foods high in complex carbs, like brown rice, chickpeas, and sweet potatoes, are also rich in fiber, which can up the discomfort level.

SKIP BEFORE YOUR WORKOUT: SPICY STUFF

In some people, hot and spicy foods—say, dishes with jalapeño peppers or hot sauce—can trigger heartburn or acid reflux, caused by acids that escape your stomach and enter your esophagus. That leads to the uncomfortable burning sensation in your throat and sourness in your stomach, which can make your workout feel lousy.

Especially on important days—like when you’re running a 5K or trying for a PR on bench—make sure you’re avoiding foods that don’t sit well with you.

“Practice what you eat just like you practice all the other skills that are involved in your sport,” Mullins suggests.

Not sure how you react to the heat? To help you recognize and remember which foods spark discomfort, keep a diet diary and take note of any adverse reactions after you eat.