One of the most effective ways to improve marathon performance isn’t super shoes, grueling workouts, hundreds of miles, or caffeine—though I’d argue that the first morning cup of coffee comes close. It’s figuring out a solid fueling plan, including taking in enough carbohydrates.
Don’t just take my word for it: Research backs up the benefits of high-carb intake for athletic performance—not only before and after workouts, but during the run itself. And as a runner who foolishly used to do most of her runs fasted (or at the very least, woefully under-fueled), I’ve found that carbs profoundly enhance my training.
Yes, I know I’m super late to the party here, but hear me out: With carbs on board, running feels like a different sport. Physically, faster paces come with less effort, and my legs actually respond with power on hills. Mentally, my motivation is higher, my mood is better, and I find myself more likely to sing along and play the air drums to my favorite playlist.
“Carbohydrates are essential for giving the body energy,” registered sports dietitian Roxana Ehsani, MS, RD, CSSD, previously told Runner’s World. “They provide the brain and the muscles with their preferred source of energy.”
That’s why you need a regular and substantial supply of this macronutrient. According to Ehsani, carbs should make up about 55 to 60 percent of your daily total calories, and they should have a place on your plate at every meal.
Additionally, while most runners know protein’s importance for maintaining muscle mass, carbohydrates play a role here, too. When we run low on carbs, our bodies utilize more fat for energy—but they also can start to break down muscle, Megan Robinson, RD, CSSD, sports dietitian and RRCA- and UESCA-certified run coach, previously told Runner’s World. And while research has shown that we can influence our bodies’ capacity to use fat for fuel, our ability to maintain pace at high intensities suffers.
When we have enough carbohydrates in our diets, our physiology naturally favors that energy source over both muscle and fat, which helps us both run better and preserve lean mass.
“Typically, anytime you’re doing a run longer than 90 minutes, your body will start to burn through glycogen. So, you have to replenish muscle glycogen through carbohydrate [intake]. If not, your glycogen stores deplete, translating to a decrease in performance—less stamina, less drive, and a faster bonk,” Robinson explains.
So you know you need carbs, but how many and how do you get enough? That’s the more complicated part of the equation. Here’s what to know, straight from sports dietitians.
How Many Carbs Do I Need?
Minnesota-based registered dietitian and marathoner Kristy Baumann, RDN, advises her athletes to consume roughly 2.3 to 5.5 grams of carbohydrate per pound of bodyweight per day when marathon training. The lower end is appropriate for lighter training days, when you’re doing runs lasting about an hour. Aim toward the upper end for periods of high training volume, like when you’re tackling long runs lasting two or more hours.
For a runner who weighs about 150 pounds and aims to consume 4 grams of carbohydrate per pound of their bodyweight, they would aim for a total of around 600 grams of carbs in a day.
Here’s what a day of their meals and snacks could look like, with ideas from Natalie Rizzo, MS, RD, a New York City–based registered dietitian and founder of Greenletes.
Breakfast
125 grams of carbs
½ cup dry oats made with ½ cup 1 percent low-fat milk and ½ cup water.
Top with ½ cup mixed berries, 1 tablespoon of nut butter, and 1 banana.
Pair with 8 ounces of orange juice.
Morning Snack
90 grams
2 Nature Valley Oats ’n Honey Bars and 4 Medjool dates
Lunch
150 grams
Sandwich with 2 slices of white bread, 3 ounces of deli turkey, 1 ounce of Swiss cheese, and tomato slices
½ cup of roasted chickpeas and 1 cup of grapes
Pair with 8 ounces of chocolate milk.
Afternoon Snack
80 grams
Medium sweet potato (microwaved), topped with cinnamon
1 ounce of dark chocolate
Pair with 8 ounces of coconut water.
Dinner
155 grams
1 ½ cups of cooked white rice and 1 ½ cups of cooked butternut squash
4 ounces of grilled chicken
Side salad (about 1 to 2 cups of lettuce and veggies combined)
Pair with 16 ounces of a sports drink.
Do I Need to Eat More Carbs Around Long Runs?
In short, yes. But according to Ehsani, you don’t need to do the same carb-load before your long run that you would for your 26.2-mile race; a “mini” carb-load can be beneficial to top off your glycogen stores.
Ehsani explains the most important thing is that you are consistently eating enough carbs throughout your training cycle, and finding foods that sit well with you. The day before and morning of your long run are ideal opportunities to practice with those foods, and to prioritize getting more easy-to-digest carbs in your meals and snacks.
The night before a long run of 2.5 hours or more, Ehsani says to fill one-half to three-quarters of your dinner plate with carbohydrates such as pasta, white rice, and potatoes. Add your favorite source of protein and—if you know they sit well with you—a serving of vegetables.
And don’t forget: Equally as important as hitting your carbohydrate needs is making sure that you’re hydrating well.
The morning of your long run—or any run longer than 60 minutes—prepare a breakfast with about 50 to 90 grams of carbohydrates, Starla Garcia, RD, a Houston-based registered dietitian and 2020 Olympic Marathon Trials qualifier, previously told Runner’s World. Runners can adjust for this as well by calculating 0.45 to 1.8 grams of carbohydrates per pound of bodyweight.
For example, a 150-pound runner who has a two-hour or longer run on their schedule will need roughly 70 to 270 grams of carbs before the run. If you’re not used to fueling prerun, start at the lower end of that range and gradually increase. Pro tip: Give yourself at least 90 minutes to two hours to digest before heading out the door.
For breakfast, some good options include a bagel with peanut butter and a banana, or a bowl of oatmeal with almond butter and berries. Top those meals with honey, maple syrup, sweetened granola, or brown sugar if you need to add more quick-digesting carbs.
Again, don’t forget to hydrate—sprinkle an electrolyte packet into your water if you suspect you’ll be sweating. Even better, your favorite sports drink can help you hit your carb needs and provide those extra electrolytes.
What About Carbs During My Runs?
The rule of thumb to remember is “fuel early and often.” This means you’ll want to start taking in gels and hydration about 20 to 30 minutes into your long run. From then on, take a gel or chew about every 25 to 30 minutes until you finish, Garcia previously told Runner’s World. Just keep in mind that it takes between 15 and 20 minutes for that fuel to get to your muscles, so it can be best to start taking those gels before you feel like you really need them.
According to Garcia, you should aim for a bare minimum of 30 grams of carbs per hour during your long runs. But depending on your body size, pace, and run duration, you may need significantly more. For example, some elite athletes perform their best when consuming more than 100 grams of carbohydrates per hour. The best way to determine your needs is to add fuel slowly to see what you can tolerate, and then adjust your fueling frequency based on how you feel during your run.
“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 the 90 grams per hour.”
If all this sounds like a lot, don’t worry about getting it perfect. You may have to experiment with different types and amounts of carbs in your diet until you find the right fueling plan to help you hit your goals on race day. Practicing fueling is part of the training, and like the training itself, it’s not always easy. Just remember: You’re in good company with thousands of distance runners on the same high-carb journey—and we’ve got plenty of breadsticks for the ride.
Morgan is a gear editor who has been with Runner’s World since 2017. She started as an intern ghostwriting The Warmup, a bygone version of the daily RW newsletter. Now, she tests and reviews anything you might find on runners’ feet-from crew socks and compression boots to carbon-plated super shoes.
A lifelong runner and shoe geek, Morgan has been chasing the perfect pair of kicks since she joined her grade school cross-country team. Since then, she ran as a Division I walk-on for the cross-country and track & field teams at the University of Delaware, where she studied English and Biology. She has one full marathon under her belt, and has raced more halfs and 5Ks than she can count.
