How To Carb Load For A Race

Greenletes / Sports Nutrition / Pre-workout / How To Carb Load For A Race

Last updated on February 21st, 2023 at 11:35 am

The ultimate guide to carb loading for your next half marathon, marathon or triathlon for maximum energy levels.

You’ve likely heard that you should carb load before a long-distance race, but there are so many questions about why loading up on carbs helps performance and how to do it properly.

Does carb loading allow you to eat pasta, bagels, bananas and rice all day? Sort of. But there are some rules to follow when carb loading to ensure you’re doing it efficiently.

What is carb loading?

Carbs are the primary fuel source for exercise, making them incredibly important for athletes. [Read more about the best plant-based carbs for athletes.] The body actually stores carbs in the liver and muscles (this is called glycogen).

Carb loading was invented in 1969 by a runner who went on to win a gold medal in the European Athletics Championship. During exercise, the body relies on two forms of carbs for fuel.

The first is dietary carbs—the ones you ate before the race—and the second is glycogen. The point of carb loading is to train your body to store up as much glycogen as possible so you have energy during long endurance activity.

Usually, glycogen stores only last for about 30 minutes during exercise, and the purpose of carb loading is to try to extend that window. It’s essentially filling up your gas tank with energy in order to reduce time to fatigue.

During long events, like marathons or triathlons, carb loading can help keep energy levels up. Well-trained athletes have higher glycogen stores than less-trained athletes. That means they can really reap the benefits of carb loading.

various whole grain examples in bowls

On a regular day, about 45-60% of calories should come from carbs, like fruits, vegetables, grains, beans and legumes. Someone who is carb-loading should increase their carbohydrate intake to about 80% of daily calories.

Although chowing down on bread and pasta may sound fantastic, eating 80% of calories from carbs is more tedious than you think (more on that later).

Ideally, aim for 4 grams of carbs per pound of body weight. For a 120 pounds person, that’s 480 grams of carbs per day.

Download the 100 best plant-based foods for runners here!

Should I carb load for a marathon?

The idea behind carb loading is to store up as much glycogen as possible for long-lasting energy during a race. You do not need to carb load for a marathon, but it can help maintain energy levels during the first few miles of the race.

Rather than burning through glycogen stores quickly, carb loading ensures that glycogen stores last a bit longer than the usual 30 minutes. After that, you will need to take in fuel to keep energy levels high. [Related: Vegan Marathon Diet: How to Fuel for Training and Race Day]

Carb loading has been proven to boost energy levels during a marathon. Without carb loading, you may need to take in fuel after the first 60 minutes of a marathon. With carb loading, you may have more sustained energy through the first 90 to 120 minutes of a race. Either way, you should ingest mid-race fuel.

When should I start carb-loading for a marathon?

Although it sounds fun to eat tons of pasta and bread every day, eating the majority of your calories from carbs will get old after a while, so you don’t want to start too soon before a race. Begin carb loading 2 to 4 days before a race to give your muscles time to build their glycogen stores.

In addition, do not exercise in the 2 to 4 days leading up to a race. In order to store up as much glycogen as possible, it’s important to take rest days. Exercise depletes glycogen stores, and this counteracts your carb-loading efforts.

What are the best foods for carbo loading?

The best foods for carb loading are healthy foods, like grains, fruits, vegetables, legumes and beans. Some people like to limit fiber while carb loading, so they don’t have any stomach issues on race day.

That said, you still need some fiber in your diet to keep the digestive system moving. You do not want to end up constipated for race day!

Use high carb grains or starchy vegetbles, like pasta, rice, bread, potatoes, corn or squash, as the base of your meal. Add beans, legumes, vegetables and fruit. Some people find that drinking juices, sports drinks, chocolate milk or coconut water can also help them take in carbs without getting too full.

Some athletes also eat sugary snacks, like jelly beans, licorice, pancakes with maple syrup, cereal, pop tarts, and energy bars. Eating more added sugar than normal is perfectly fine for the 2 to 4 days of carbo-loading.

I recommend avoiding fried or fast food during the carb-loading phase, since they can upset your stomach.

Do I need to carb load for a 10k?

There’s no need to carb load if you’re participating in a low intensity event or something that is shorter than an hour, such as a 5k or 10k run. If you carb load for these events, you won’t use all the carbs you consume and might even gain weight. 

Carb loading is best before a half marathon, marathon, triathlon, long bike race, long swim or any continuous activity that lasts longer than 90 minutes.

Carb loading meal plan

Here is an example of a carb loading meal plan for a 150-pound person. They will need to eat around 600 grams of carbs per day.

5 carb loading meals to eat before your next race.


  • 1/2 cup dry oats, made with 1/2 cup low-fat milk (1%) and 1/2 cup water. Topped with 1/2 cup mixed berries and 1 tablespoon of nut butter
  • 1 banana
  • 8 ounces orange juice
  • Carb total: 125 g

Mid-morning snack:

  • 2 Nature Valley Oat n Honey Bars + 4 Medjool Dates
  • Carbs: 90 g


  • Sandwich: 2 slices of white bread, hummus, sliced veggies
  • 1/2 cup roasted chickpeas
  • 1 cup grapes
  • 8-ounces chocolate milk (or soy chocolate milk)
  • Carb total: 150 grams

Mid-afternoon snack

  • Medium sweet potato (microwaved), topped with cinnamon
  • 1 ounce dark chocolate
  • 8 ounces coconut water
  • Carb total: 80 gram


  • 1.5 cups cooked white rice + 1.5 cup cooked butternut squash + 4 ounces tofu or tempeh
  • side salad (about 1-2 cups of lettuce and veggies combined)
  • 16 ounces sports drink
  • Carb total: 155 g


  1. Ann

    As a vegan, my diet consists of approximately 70% of carbohydrates. At my last marathon I felt as though my carb loading wasn’t very effective.
    How do you carb load prior to a marathon if your diet already consists of so many carbs?

    • Natalie Rizzo, MS, RD

      That is a GREAT question! You can increase your carbs even more in the 3-7 days leading up to a marathon. Aim for 80-90% carbs, if possible. It’s difficult to do, so try adding in carbs in beverage form, like juice, sports drink, coconut water, etc. And you can also add a little bit of extra sugar to your meals, like honey or maple syrup.


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I’m Natalie Rizzo, an NYC-based Registered Dietitian.

My mission is to help everyday athletes fuel their fitness with plants.

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