Don’t Overthink Your Long-Run Fueling. Here’s Exactly What and When to Eat to Perform Your Best, According to Experts
As any half or full marathoner knows, the best time to practice fueling for race day is your long-run days. This helps you find which foods work for you and how to fuel enough to avoid feeling sluggish and slow or bonking. It can also help you figure out how to avoid eating too much or too close to takeoff, leading to cramping, uncomfortable fullness, and other gastrointestinal problems that can derail a run.
As figuring out the best plan for you can take some trial and error, where do you even start figuring out what to eat before a long run for optimal performance? And when should you eat before you head out?
In this guide, we answer all your questions about why it’s so important to eat before a long run, what you should choose, and how to time it right—well ahead of race day.
Why should you eat before a long run?
Susan Paul, exercise physiologist and former program director for the Orlando Track Shack Foundation, says eating before a long run provides two very important functions. For starters, it provides energy, which you need after a night of sleeping and fasting. “Think of it as filling up the gas tank of your car—it’s not completely empty, but you want to top it off,” she explains.
The second important function of eating prior to a long run is that it keeps you comfortable. Paul explains that digestion can be challenging during runs because the body diverts bloodflow away from internal organs and shunts it to the large muscles of the body. This helps supply those working muscles with oxygen-enriched blood to meet the demands of running. But the result is that areas, such as the gastrointestinal tract, receive less bloodflow during exercise.
Food present in the stomach, however, recruits bloodflow for digestion. This helps the stomach and GI system retain more bloodflow when the shunting process from running happens, keeping the GI system in better working order, Paul says. “When no food is on board, blood flow is immediately diverted away. The GI system shuts down, making eating on the run very difficult,” she adds.
“The amount of blood flow that is diverted away from internal organs is usually correlated to the intensity of the exercise. In addition, the longer the run, the more time these organs receive less blood flow, which can contribute to GI issues on high-mileage days,” Paul says.
When and how much should you eat before a long run?
It’s not as simple as grabbing a bagel and lacing up. Paul recommends eating about one to two hours before the run. “Low-fat and low-fiber foods are the best choices for most runners, but experimenting with different foods is important so you can figure out what works best for you,” she says. “The goal is that by race day, you will have your personal nutritional plan all figured out.”
Paul also says a prerun breakfast should contain at least 200 to 300 calories, predominantly from carbohydrates.
Starla Garcia, RD, a registered dietitian and 2020 Olympic Marathon Trials qualifier, recommends fueling with 50 to 90 grams of carbohydrates for runs longer than 60 minutes. “Runners can adjust for this as well by calculating 1 to 4 grams of carbohydrates per kilogram of bodyweight,” she says.
For example, Garcia says a 140-pound runner who has a two-hour or longer run on the schedule will need roughly 63 to 254 grams of carbs before the run.
Start with the lower end of the calorie and carb range (if you’re not used to fueling prior to running) and gradually increase it as needed. “Better to go minimal first than to overload the system,” Paul says. “Think: small meals that contain primarily easily digestible carbohydrates with some protein—about a 3:1 ratio of carb to protein works best.”
What foods should you eat before a long run?
Garcia says if you’re short on time, consider a simple carbohydrate-based option like an energy gel and a sports drink. This combination will get you hydrated and fueled within 30 minutes of your running time.
If you have more time to digest, Garcia recommends that runners aim for a meal or snack that meets their carb needs (as a reminder, that’s 1 to 4 grams of carbs per kilogram of bodyweight). Prioritize a full breakfast—or lunch, if your run is much later.
As for exactly what to eat, Garcia suggests avoiding foods such as cruciferous vegetables, high-fat foods, or fried-food options to avoid GI distress. Stick with those simple carbs and a little protein instead.
Garcia recommends fueling with one of these five options before your next long run:
- 4 full graham crackers, 1 banana, and 1 serving of sports drink
- 1 packet of Belvita breakfast biscuits, 1 banana, and 1 serving of sports drink
- 2 slices of toast with nut butter and 1 banana
- 1 cup of oatmeal cooked with 1 banana and 2 tablespoons of maple syrup
- 2 Pop-Tarts with 1 serving of sports drink
How much should you hydrate before a run?
Now that you know how to fuel, you can’t forget hydration. Garcia says to drink between 8 and 12 ounces of fluids at least 30 to 60 minutes prior to running. Because we all know that chugging water before you head out the door isn’t going to end well, make sure to sip slowly. “Drinking too much water can cause sloshing or cramping to occur,” she says.
Garcia adds that consuming some electrolytes in your fluids for longer training sessions is a good choice to help improve gut absorption and heat tolerance. The addition of electrolytes can even be beneficial in colder months—even if you’re not sweating as much—because it may encourage you to drink more fluids.
“Consuming electrolytes prior to exercise can prevent you from starting a run dehydrated and also helps you avoid becoming dehydrated during the run,” Garcia adds.
What and when should you eat during a long run?
The minimum amount of fuel you should take in per hour while running is about 30 grams of carbs, Garcia says. The maximum is about 90 grams or, in some cases, 120 grams of carbs per hour. But these numbers can vary depending on your body, intensity, timing, how you feel, and more.
“The recommended time to implement or add fuel will also vary depending on the type of fuel a runner chooses,” Garcia adds.
It’s smart to ingest your fuel in increments to help you achieve 30 grams (or more) of carbohydrate per hour. That means ingesting a little fuel at a time, say every 15 to 25 minutes or so, after the first half hour.
“Typically for marathons, most runners can tolerate a gel every 30 minutes,” Garcia says. “I would recommend moving to [taking in fuel] every 20 minutes [if you can tolerate it] to get closer to 90 grams of carbs per hour.”
Jennifer Acker reports on a wide range of health and wellness topics for Runner’s World and Bicycling. She’s passionate about delivering journalism that enriches the lives of readers. Jennifer is a lifelong runner—with several half marathons, and a few marathons under her belt, certified yoga instructor, and having grown up in the Pocono Mountains, always has a mountain bike and pair of skis ready for the perfect fall or winter day.
Dr. Namrita Brooke is a full-time endurance sport coach and sport nutritionist advising active individuals and amateurs to professional athletes. She is also an adjunct professor in the Department of Movement Sciences and Health at University of West Florida. Professionally, she also serves on the Board of Editors of the Sports Nutrition Care Manual and remains involved in nutrition and exercise-related research, student mentorship, and coach development. Namrita's personal athletic experience ranges from ultra-endurance mountain biking to off-road triathlon, cross-country mountain bike racing, gravel cycling, duathlon, cyclocross, running, and trail running. Her research background includes hydration and sports drink research, and the interaction of nutrition, physical activity, and the brain.