Carb Loading for Marathons and Ultramarathons

January 22, 2023
3 Minutes
Nick Hancock

Carb Loading for Marathons and Ultramarathons

Have you spent months training and preparing for an upcoming marathon or ultra run, only to hit a wall during the race? If so, you're not alone. Runners constantly suffer from "bonking", aka hitting a wall and gassing out mid-race.

But what if there was a science-backed way to improve performance that had nothing to do with running?

Enter carb loading! Carb loading is a popular practice among long-distance runners, and for a good reason. But what is carb loading, why is it important, and how can you do it correctly before race day?

What Is Carb Loading?

The goal with carb loading is simple: to improve performance by having more energy in your muscles as you start the race. It involves increasing your carbohydrate intake in the days leading up to your race while tapering off other foods.

Why Is Carb Loading for Runners Important?

Carb loading helps runners by allowing the body to store more glycogen (a fuel source). Glycogen is the primary energy source used by our muscles during intense exercise, so it's crucial to ensure adequate amounts are available during your race.

This gives the body a reserve of energy to tap into during long runs, helping you avoid hitting the wall and powering through until the end. When done correctly, carb-loading before a marathon can give you an edge over the competition.

How to Carb Load for a Marathon or Ultra Run

Carb loading isn't about eating a massive bowl of pasta the night before your race. It's a gradual process, and it takes planning. Here are some tips for successful carb loading:

  1. Increase your carb intake gradually, starting 4-5 days before the race.
  2. Focus on complex carbohydrates. Three days before the race, aim to eat around 7-12 grams of carbohydrates per kilogram of lean body weight per day. 
  3. Drink lots of water to stay hydrated. Drink around 8-10 glasses of water throughout the day before race day. This will help your body to flush out any toxins.
  4. Avoid excess fibre and protein, as these will slow carb-loading.
  5. Avoid high-fat foods as these will not provide enough long-term energy.

Foods To Eat When Carbohydrate Loading

When carb loading, it's important to focus on complex carbohydrates since they will provide a steady supply of energy. Some great foods to include in your carb-loading diet are:

  • Whole wheat bread and other whole grains (some sources will suggest white bread and pasta, but personally I find it bloating and its also less nutrient dense!)
  • Potatoes
  • Oats
  • Legumes such as beans, peas, and lentils
  • Fruit such as apples and bananas
  • Starchy vegetables like sweet potatoes, squash, and carrots

One final tip is perhaps seen as an unconventional one. Try introducing some sugary foods around three days before a race, as it's one of the best ways to get your glycogen stores up quickly!! A personal favourite of mine is carb loading with Oreos! A bag of Haribo are also a nice treat!

Stay Fuelled on Race Day

Carb loading isn't guaranteed to land you in first place, but if done correctly, it can give you an edge over other runners that don't utilize it. With proper nutrition and hydration in the days leading up to a marathon or ultra race, you can ensure that your body is well-fueled and ready to go on race day.

For more information on carb-loading or if you're ready for expert coaching to improve your running performance, contact me at

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