If you’re a runner, you’ve likely had a prerace pasta dinner—or if you’re running your first race, you’ve at least heard other runners talk about that important meal. That talk often comes with a discussion on carb loading a.k.a. filling up on carbohydrates so your muscles get the glycogen they need for energy come race day.
Many runners turn to pasta, rice, potatoes, or other high-carb foods before a half or full marathon to get the energy they need to cover 26.2 or 13.1 miles. But while many runners might know they should fill up on carbs, figuring out which ones, how many, and when to eat them can seem a little overwhelming to decipher.
“When I go to marathon expos, I’m amazed how many people haven’t carbo-loaded properly,” says Monique Ryan, R.D., author of Sports Nutrition for Endurance Athletes. “Runners train so hard and then arrive with a huge handicap.”
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To help you avoid that handicap and instead show up to the start filled with energy, here’s your guide to carb loading, including what that means and how to maximize the benefits.
Carb Loading: A Science
When you eat a bowl of spaghetti, most of the carbs are stored as glycogen in your muscles and liver. Glycogen is your body’s most easily-accessible form of energy, though it’s not the only source, Ryan says. During a half marathon or full marathon you burn both glycogen and fat. But the latter is not as efficient, which means your body has to work harder to convert it into fuel.
When you run out of glycogen during a race you hit “the wall.” Your body has to slow down as it turns fat into energy. Benjamin Rapoport, M.D., Ph.D., a neurosurgeon and a 2:55 marathoner, is intimately acquainted with the wall—he hit it so hard at the 2005 New York City Marathon he decided to study how to avoid it in the future.
“Proper carb loading—or filling your muscles to the brim with glycogen—won’t make you faster, but it will allow you to run your best, and, if you race smartly, avoid the wall,” he says.
When should you carb load?
Carb loading is a numbers game. It’s easy to execute (pass the bread, please), but not all races require it. Shorter distances, such as 5Ks or 10Ks, don’t require it because it’s unlikely you’ll deplete the fuel in your muscles in the time it takes to complete those distances, says Pamela Nisevich Bede, R.D., sports dietitian and author of Fuel the Fire.
However, if you’re going to be running for longer than 90 minutes, you need to be proactive. That’s where carb loading comes in, helping your body prep for the work ahead by storing the energy you need to make it through the miles.
What are the best foods for carb loading?
“I’m very utilitarian,” Rapoport says. “I eat rice for breakfast, lunch, and dinner.” But runners don’t need to be so restrictive. Tortillas, oatmeal, bread, pancakes, waffles, bagels, yogurt, and juice are all easy-to-digest options that make for smart carb loading choices.
Fruits are also high in carbs but they’re also high in fiber—and too much of that nutrient can cause stomach trouble midrace. “Bananas are a low-fiber choice,” says sports nutritionist Ilana Katz, R.D., a dietitian based in Atlanta. “And you can peel apples, peaches, and pears to reduce their fiber content.”
Katz also gives her clients permission to indulge in white bread and baked potatoes without the skin since both are easily digested.
There’s a reason Michael Scott’s fettuccine alfredo carb loading in The Office didn’t go so well: Sure, the pasta provided carbs, but the creamy, fatty sauce was pure trouble. High-fat foods, such as oils, butter, and cheese, as well as those that contain high amounts of protein, fill you up fast and take longer to digest than carbohydrates, Ryan says. That can rest heavy in your gut, and spell serious GI trouble midrace.
How many carbs should you eat to load up?
You can’t completely fill your muscles with glycogen from just one meal, “which is why you should start carb loading two or three days before your race,” Ryan says. Since you’re running very few miles during this time, the glycogen will accumulate in your muscles. At this point, 85% to 95% of your calories should come from carbs, Katz says. Ryan recommends eating about 4 grams of carbs for every pound of body weight. For example, a 150-pound runner should consume 600 grams—or 2,400 calories—of carbs per day.
During his research, Rapoport developed an even more precise formula that factors in variables including age, resting heart rate, VO2 max, and predicted finishing time. It’s important to keep in mind that you’re most likely not eating many more calories per day than you were during the thick of your training—it’s just that more of those calories are coming from carbs.
If you step on the scale while you’re carb loading, be prepared to see a number that’s at least four pounds more than your usual weight. The extra pounds mean you get a gold star for carb loading properly. “With every gram of stored carbohydrate, you store an extra 3 grams of water,” Katz says. That means your body will be hydrated and fueled as you start the race, ensuring you cross the finish feeling strong.
What does a day of carb loading look like for a runner?
According to Natalie Rizzo, M.S., R.D., founder of Greenletes, you should shoot for about 4 grams of carbs for every pound of body weight. Here’s a menu example for the average 150-pound runner.
Breakfast
1/2 cup dry oats made with 1/2 cup 1% low-fat milk and 1/2 cup water. Top with 1/2 cup mixed berries and 1 tablespoon of nut butter, 1 banana, and pair with 8 ounces of orange juice (125 grams).
Mid-morning snack
2 Nature Valley Oats ’n Honey Bars and 4 Medjool dates (90 grams).
Lunch
Sandwich with 2 slices of white bread, 3 ounces of deli turkey, 1 ounce of Swiss cheese, and tomato slices; 1/2 cup of roasted chickpeas; 1 cup of grapes; and pair with 8 ounces of chocolate milk (150 grams).
Mid-afternoon snack
Medium sweet potato (microwaved), topped with cinnamon; 1 ounce of dark chocolate; and pair with 8 ounces of coconut water (80 grams).
Dinner
1 1/2 cups of cooked white rice; 1 1/2 cups of cooked butternut squash; 4 ounces of grilled chicken; side salad (about 1 to 2 cups of lettuce and veggies combined); and pair with 16 ounces of a sports drink (155 grams).
Carb Total: 600 grams
How should you time your carbs?
Here’s what to do before race day to ensure your tank is full.
6 weeks before... Begin practicing carb loading
Two or three days prior to your longest run, start eating more carbs and less fat and protein. “You’ll get a sense of what foods agree and disagree with your stomach,” Katz says.
One week before... Make a plan
“A plan is especially important if you’re traveling to a race,” Ryan says. Pack plenty of snacks, such as energy bars, pretzels, and crackers, and check menus online and make restaurant reservations.
Two to three days before... Switch to mostly carbs
From now through your race, 85% to 95% of your diet should be carbs. You should also eat after taper runs. “That is when muscles are primed to store glycogen,” Rapoport says.
The night before... Don’t overdo the carb load
Dinner should be relatively small, but carb-heavy. Eat on the early side so you have lots of time to digest. “You want to wake up race day hungry—not full from the night before,” Ryan says.
Race morning... Have a good breakfast
Three hours before the start, eat 150 grams of carbs, like a bagel and yogurt or sports drink and oatmeal, says Ryan. Early race? “Get up at 3 a.m., eat, and go back to bed,” she says.
How to top off your carb tank during a race
While races that are finished in less than 90 minutes don’t require carb-loading in the days prior to the event, any efforts over 60 minutes may require an extra shot of energy during the race.
One of the best ways to do that is by consuming a sports drink, an energy gel, or an energy chew. Their carbs come in the form of simple sugars, which are your body’s preferred source for quick, efficient fuel during exercise, says Bede. Products that contain two kinds of sugars, such as glucose and fructose, are absorbed even quicker.
Take a drink, gel, or chew every 30 to 45 minutes for runs lasting 60 minutes or longer to top off your glycogen stores. Aim for 120 to 240 calories, or 30 to 60 grams of carbs. Many of these options also include electrolytes—which aid in maintaining a proper fluid balance—and caffeine, which can help you power through the last few miles.
Top marathoners Eliud Kipchoge, Galen Rupp, and Des Linden have relied on Maurten Drink Mix (without endorsement contracts). It contains more carbs than most sport drinks, has no artificial flavors or preservatives, and forms a hydrogel when it reaches the stomach, helping to guard against GI issues.
4 Top-Off Options for Midrace
For Tough Workouts: Skratch Labs Sport Hydration Drink Mix
For When You Want to Chew: Clif Bloks Energy Chews
For Picky Tasters: GU Energy Gels
