You've Been Carb-Loading Wrong — Here's How a Dietitian Wants You to Fuel Before a Run

Does carb-loading actually work? It's a fair question when you consider your running diet. Excess carbs can lead to weight gain (especially simple carbs, such as sugar or white bread), even when you're running miles and miles every week. Carbs are crucial for a runner (we'll get to that later), but overdoing it can lead to extra pounds; it's why some people actually gain weight when they start to run or train for a race. So is it worth it to try carb-loading? Does this classic strategy of pushing carbs actually pay off — and if so, how? For the answers, POPSUGAR turned to registered dietitian Audra Wilson, LD, of the Northwestern Medicine Metabolic Health and Surgical Weight Loss Center at Delnor Hospital.

What Is Carb-Loading?

When you carb-load, you're essentially increasing your carbohydrate intake for anywhere from one to three days before your run, race, or competition. The premise makes sense, scientifically speaking. Carbs are your body's main source of glucose, stored as a compound called glycogen. Glycogen, in turn, is used as energy in workouts and is especially important during sessions that burn a ton of calories, like running. "The thinking would be to load up the glycogen stores in your muscles, so that you'd have that stored energy for the competition," Audra explained. "So we'll do a high dose of carbohydrates in the days preceding the event to make sure our glycogen stores are completely full and topped off." This is why carb-loading is also sometimes known as "glycogen supercompensation"; you're "overcompensating" with glycogen in order to feel good during a race.

Eating carbs and having adequate glycogen stores can help you postpone fatigue, improve your endurance, and maintain a steady pace for longer, Audra told POPSUGAR (though they won't necessarily help you run faster). Carb-loading, though, essentially means that you're eating more carbs than your body is used to. You do want to be consuming carbs in the days leading up to your run, but where should you draw the line?

When and How to Carb-Load

The decision of whether to carb-load or not comes down to how long your run is and what your body is used to, Audra said. "It's not necessary unless your event's going to exceed about 90 minutes," she told POPSUGAR. "So if you're doing an event that's 30 to 60 minutes, it's really not something that you'd need to think about."

She recommended consuming five to 10 grams of carbohydrates per kilogram of your bodyweight per day, over the one to three days before the events — around the same amount as what you're already consuming. For the math people, that means dividing your bodyweight (in pounds) by 2.2 to convert it to kilograms. Multiply that by anywhere from five to 10 to get the total grams of carbohydrates you should eat in a day. From there, you can divide by the number of meals in a day to get the amount of carbs you should eat at each meal. A 150-pound woman eating 10 grams of carbs per kilogram, for example, would need about 680 carbs per day before a race. Audra also noted that these should also be rest days; otherwise, you'll burn off the glycogen stores you're trying to fill up.

You also shouldn't wait until the night before your race or workout to get your full amount of carbs for the day. "Space it out accordingly so it's never too much at one time," Audra told POPSUGAR.

That's because eating too many carbs at one time can actually have a negative effect on your athletic performance. "If you just suddenly eat a meal that's really carbohydrate-heavy, you can feel stiff. It can make you feel a little fatigued, and you might not sleep very well," Audra explained. That goes for the idea of carb-loading in general, too. If you overwhelm your body with carbs in the days before your event, and your body isn't used to it, it can negatively impact your performance. You might have a slow start to the race or feel lethargic, Audra explained. "That's why you don't necessarily want to do that without trying it first and just seeing how you feel with it." In other words, that giant prerace pasta might not help you cross the finish line in any better shape if it's not something your body is used to digesting.

If your run or workout is going to go over that hour-and-a-half threshold, and you feel you need it, Audra said it's fine to experiment with consuming more than five to 10 grams of carbs per kilogram of bodyweight — again, as long as your body responds well to it and as long as you're spacing out the carbs throughout the day. She recommended trying out the higher intake before a long run a few weeks prior to your event so you can see how your body responds, help it acclimate, and adjust your carb levels as needed.

"It shouldn't be, 'I'm trying this for the first time. I'm going to have a huge spaghetti dinner with sauce and meatballs the day before a competition when I've never don't that before,'" Audra said. "You don't know how that's going to impact your gastrointestinal tract, your bowel movements, or just the way you feel in general. Balance is really the key."

Want more on what you should eat as a runner? Check out our tips on what to eat before a run and what you definitely want to avoid.