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Eating a large meal right before a run can lead to cramping and digestive problems. It can also make you feel sluggish during your run.

As a general guideline, it’s recommended that you wait 3 to 4 hours after a large meal before running.

If you’ve had a small meal or snack, wait a minimum of 30 minutes or preferably 1 to 2 hours before going for a run.

Keep in mind that everyone is different. You may have more energy eating a small snack just before going on a run, or you may have no trouble when you eat a meal before a workout.

Read on to learn more about eating before and during a run.

A light snack before exercise can help you get through your run with plenty of energy and keep your blood sugar level from crashing. What to eat may depend on what time of day you usually go for a run.

Morning run

If you run in the morning, you may not have enough time to eat a meal hours before hitting the road. But your body likely hasn’t had any other food since the night before.

That’s why it’s important to try to eat a light snack or breakfast 30 to 60 minutes before heading out. Choose foods that contain carbohydrates and protein.

If you run in the morning, try the following snacks:

  • banana with a tablespoon of nut butter
  • energy bar or low fat granola bar
  • small yogurt and fruit
  • fruit smoothie
  • whole grain bagel
  • oatmeal

Lunchtime run

If you run at lunchtime, fuel up with a hearty breakfast 3 to 4 hours before your run. Then 1 or 2 hours before running, snack on:

  • a bowl of cereal or oatmeal
  • half of a nut butter sandwich
  • small smoothie
  • a handful of nuts, such as cashews, pistachios, or almonds

Late afternoon or evening run

If you run in the late afternoon or evening, you may experience hunger and fatigue post-lunch without a pre-workout snack to tide you over until dinner.

This is especially true if you aren’t planning to eat until late because of your run.

Snack on the following in the afternoon 1 to 2 hours before your evening run:

  • crackers and a cheese stick
  • energy bar or low fat granola bar
  • half of a nut butter and jelly sandwich

You’ll generally only need water — or a sports drink — during your workout for runs under 1 hour.

For runs longer than an hour or very intense exercise, you’ll need to take in a form of carbohydrates, such as a sports drink or energy gel, for every hour you’re running for longer than 75 minutes.

Experiment to find what works best for you during long runs.

For example, some runners may eat half of an energy gel, two energy chews, or a few energy beans every 30 minutes on runs longer than an hour. Follow these up with plenty of water.

Dehydration can lead to gastrointestinal (GI) discomfort in runners, including cramps, bloating, and stomachaches.

To prevent cramps, drink water or a sports beverage every 15 to 30 minutes while running, avoiding high fiber foods the night before and the morning of a run. They can also lead to cramping and GI trouble.

You may experience nausea or vomiting during or after a challenging workout. Nausea can occur in runners for a number of reasons, including (1):

To avoid nausea while running, drink plenty of water, especially on hot days. It’s also important to cool down properly, so your body has time to adjust after a run.

You may find eating a light snack 30 minutes before or immediately after running can help prevent or stop nausea.

Runners need to drink water, especially on hot days. Follow these guidelines to help prevent dehydration and stay safe while running:

  • Drink around 2 to 3 cups (473 to 710 mL) of water 2 to 3 hours before your workout.
  • Drink around 1/2 to 1 cup (118 to 237 mL) of water every 15 to 20 minutes during your run. You may require more depending on your body size and on hot days.
  • Drink around 2 to 3 cups of water after your run for every pound (0.5 kilograms) of weight lost during your run. Weight loss immediately following a run is a sign that you’ve lost water weight.

For runs longer than an hour, a sports drink is a smart choice. Sports drinks may help you recover by helping you maintain electrolyte balance and providing energy from carbohydrates (2).

Though food is fuel for runners, eating a large meal too soon before going out for a run can lead to digestive problems like cramping or diarrhea.

Instead, try to wait at least 3 hours after a meal before going for a run. Eating a light snack like a piece of fruit, yogurt, or half of a peanut butter sandwich could give you energy to get through your workout.

When you get home from your run, it’s essential to refuel with a light meal or protein shake and rehydrate with water or a sports drink.