How To Carb Load For A Race

Greenletes / Sports Nutrition / How To Carb Load For A Race

Learn how to carb load for your next half marathon, marathon or triathlon.

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 give you a license 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 something called glycogen, which is in the liver and muscles.

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 stored glycogen. The point of carb loading is to train your body to store up as much glycogen as possible so you have energy on reserve.

Usually, glycogen stores only last for about 30 minutes during exercise. The purpose of carb loading is to try to extend that 30-minute window and make sure you have as much glycogen stored as possible. It’s essentially filling up your gas tank with energy in order to reduce time to fatigue.

Well-trained athletes have higher glycogen stores than less-trained athletes. That means they can really reap the benefits from carb loading.

various whole grain examples in bowls

What is the best food for carb loading?

Quite simply, the best foods for carb loading are easy to digest and rich in carbs (obviously).  Some of my top recommendations for what you should eat when carb loading are: 

  • Whole grains: Pasta, bread, oatmeal, rice, cereal & granola
  • Starchy vegetables: White potato, sweet potato, corn, squash  
  • Fruit & fruit juice 
  • Legumes & beans 
  • Milk & yogurt 

How much carbs should you eat when carb loading?

About 80% of your daily calories should come from carbs. The average carb intake is 45-60% of daily calories, so that’s quite a bit more. Although chowing down on bread and pasta may sound fantastic, eating 80% of calories from carbs is more tedious than you think.

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

Another slightly different recommendation suggests eating 4 grams of carbs per pound of body weight. For a 120 pounds person, that’s 480 grams of carbs per day. That means most of your diet will consist of grains, fruits, vegetables, legumes and beans. Drinking juices, sports drinks or coconut water can also help reach this high level of carb intake.

Avoid the unhealthy types of carbs, like fried food, desserts and soda. That said, it’s not the end of the world if you want to add a cookie or piece of candy to your daily carb loading routine.

When should you start carb loading?

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.

The other rule to keep in mind is that exercising depletes glycogen stores, and this counteracts your carb loading efforts. That means you need to rest during the 2 to 3 days leading up to the race.

For what events do I need to carb load?

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 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.

Do I need to 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 surely 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, the body turns to any dietary carbs to fuel for the first 60-90 minutes of a race. 

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 will need to take in mid-race fuel, but carb loading has been proven to boost energy levels during a marathon.  

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.


  • 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
  • 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


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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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