You've probably heard the old adage that warns against jumping into the pool right after eating. Though it's probably alright to swim after a meal, you may want to wait at least 30 minutes to avoid muscle cramps.
But just how long should you wait to go for a run or lift weights after eating? Here's what dietitians recommend to properly fuel for your workout.
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You shouldn't exercise right after eating a big meal
According to Melissa Rifkin, a registered dietitian and owner of Melissa Rifkin Nutrition in New York City, eating before a workout is critical to perform your best. But what that looks like will depend on the type of workout and size of your meal.
There are a few common rules of thumb you should follow. Basically, the bigger the meal, the more time you should wait to work out, says Amie Rowe, RD, at Duke University Hospital.
"Eating a heavy meal immediately before a workout can cause GI discomfort — like bloating and cramping — and will not result in optimal performance due to competing demands between your muscles and digestive system," Rowe says.
Instead, Rowe recommends eating a low-fiber snack about 30 to 45 minutes before engaging in short, vigorous exercises like high-intensity interval training or weight-lifting. These easily digestible carbohydrates will break down quickly to provide fuel: bananas, nut butter on toast, yogurt and granola, or energy bars.
For high-endurance activities like running or swimming, you'll need to store up more energy longer before your workout. Rowe recommends a mix of carbohydrates and protein two to three hours before exercise, such as a whole wheat bagel with peanut butter or yogurt with fruit.
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How long to wait before an extensive workout, like a marathon
Distance runners will also want to eat high-carbohydrate meals well in advance of a marathon. Some dietitians recommend carbo-loading two to three days before a race with pasta, rice, and potatoes.
With physical activities sustained over long periods of time, the body uses stored carbohydrates and fats for energy consumption, and Rowe says you'll need to load up ahead of time to stay fresh for the final miles.
"When there are no carbohydrates readily available in the bloodstream, the body relies on energy stores called glycogen, which can get depleted during an intense or long exercise session and hinder your performance," Rowe says.
Just make sure you don't show up to the race hungry — a granola bar or banana 30 minutes to one hour before you head to the starting line should do the trick. And you should probably stay away from any high-fat foods immediately before exercise.
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Insider's takeaway
Ultimately, it's up to you to pay attention to how different foods affect your workout performance, and you should take note of how you feel with varying lengths of time in between eating and exercising.
"Everyone is different in what their body can tolerate," Rifkin says. "It is best to try different meal or snack combinations to see what makes you feel your best so you can stay strong and have a great sweat session."
Lukas Southard is a contributor to Insider.
