What is carbo-loading, how to do it, and why? And does it make you better in competition?

Carbo-loading has been an important part of competition build-up for endurance athletes for decades. But it’s been a long time since carbo-loading meant eating bread and spaghetti “ad nauseum” for a week or more. 

Correct carb loading can provide an excellent competitive experience, and it is neither too late, complicated, nor particularly risky to carbo-load with good results to Marcialonga on Sunday. 

But what is carbo-loading, how to do it, and why? This is what the nutrition expert says.

Kristian Grue, a Sports Scientist focused on nutrition, is like most athletes: concerned with nutritional optimization, timing, execution, and details in general. Grue believes skiers, specifically long-distance skiers, have much to gain from well-executed carbo-loading. 

What is carbo-loading?

The body converts carbohydrates from your diet into glycogen which can be stored in the muscles. “Carbo-loading” is an expression used to fill the glycogen stores in the muscles, so they are filled up for the start of the competition.

In short, “carbo-loading” is about prioritizing the intake of carbohydrates in favor of other energy sources for a period of time to ensure that the glycogen stores in the muscles are completely full. This is often done as part of a competitive run-up in endurance sports. 

Why carbo-load?

Carbohydrates are converted to glycogen, the most crucial energy source at moderate to high intensity. After consuming carbohydrate-rich food, the body builds up a store of glycogen in the muscles and liver. If you line up at the starting line with peak glycogen stores, you can maintain the intensity and speed for longer. 

“You can compare car charging with driving an electric car. If you start the travel with a fully charged battery, you have a certain range at a certain speed. If you start with a partially full battery, the range with the same performance will be reduced. You have to slow down to get where you’re going,” explains Grue.  

How to carbo-load?

Carbo-loading is very simple: 

“Eat mainly carbohydrates, eat well and sufficiently, but avoid overeating,” says Grue.

“Before, it used to be that you started carbo-loading a week before the competition. But now we know more about how the body stores glycogen, i.e., carbohydrates in the muscles. What we see now is that you don’t need more than 22 hours to fill up empty glycogen stores, says the nutrition expert, and explains: 

“The muscles have a limited ability to store glycogen. That ability is trainable. But in any case, you cannot fill the ‘storage’ more than full. So 48 hours is more than enough to carry out an effective carbo load.” 

How to carbo-load? 

Grue goes through a typical “carbo-loading” ahead of longer endurance competitions to ensure that you start with peak glycogen stores in the muscles. 

Personally, Grue starts the carbo-loading in the last 72 hours before the start. 

“I usually start the carbo-loading 72 hours before the competition. Then I start cutting back on fat and protein as energy sources in favor of carbohydrates. I also cut down on carbohydrate sources with a lot of fiber,” he says. 

In the last 48 hours before the start, Grue prioritizes carbohydrates even more. 

“The idea is that the carbohydrates should be more refined,’ i.e., white bread, white rice, and plain pasta.” 

For Grue, the main meals can look like this: Breakfast can be oatmeal or slices of bread with toppings such as jam, chocolate spread, or brown cheese, but no cold cuts. For lunch, he eats white rice or pasta with some fish or chicken, but the focus is on carbohydrates, i.e., rice or pasta. Similar to dinner. 

“There will be some protein, and even bread and rice contain some protein. But for protein sources, I choose as light and lean as possible and avoid red and fatty meat products,” says Grue. 

In the last 24 hours before the start, the nutritional intake is almost exclusively about easily digestible carbohydrates: as little fiber as possible and as little fat and protein as possible. 

“On the last day, I only eat white bread. For lunch, there is often pasta, and for dinner, perhaps a pizza, but then with minimal topping. It’s pizza with tomato sauce and just a tiny amount of cheese,” says Grue. 

For breakfast before the start of the competition day, Grue often eats oatmeal made from oats he has brought from home. This is because he wants to be sure that he does not ingest anything that he is not already familiar with. 

“The most important thing is that you eat something you have eaten before competitions and with which you have a good experience,” says Grue. 

In the last hour before the start, you can also top up with a sports gel, preferably with caffeine. 

Are there any typical pitfalls or things you see athletes often do wrong when carbo-loading? 

“Yes. Many people think they must eat a lot. But in the last days before competitions, you usually cut back on the amount of training, so you have a lower energy requirement than usual.”  

And no, it is neither too late nor particularly risky to carbo-load with good results to Marcialonga on Sunday.

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Facts About Carbo-Loading

• Carbo-loading is effective for endurance competitions lasting 90 minutes or longer.
• By increasing the supply of carbohydrates before the competition, the body will have more energy in the form of carbohydrates stored in the muscles.
• Requires adaptation of diet and training during the carbo-loading period, which starts from 72 to 48 hours before the competition. Reduce the amount of exercise while increasing your carbohydrate intake.
• It is recommended to take between 10 to 12 grams of carbohydrates per kilogram of body weight per day. For a person of 70 kilos, that means between 700 and 740 grams of carbohydrates. 
• Reduce the intake of proteins and fats to a minimum. 

(Source: Olympiatoppen, Data Sport )

The upcoming Ski Classics Pro Tour event is Marcialonga, a 70km classic technique event in Italy on January 29.

Ski Classics Pro Tour Season XIV (2022/2023)

• Event 1: December 10, 2022 – Bad Gastein PTT, Bad Gastein, Austria, 15km
• Event 2: December 11, 2022 – Bad Gastein Criterium, Bad Gastein, Austria, 35km
• Event 3: December 17, 2022 – La Venosta Criterium, Val Venosta, Italy, 40km 
• Event 4: January 14, 2023 – Pustertaler Ski Marathon, Sexten, Italy, 62km
• Event 5: January 15, 2023 – Prato Piazza Mountain Challenge, Niederdorf, Italy, 32km
• Event 6: January 21, 2023 – Engadin La Diagonela, Engadin Valley, Switzerland, 48km 
• Event 7: January 29, 2023 – Marcialonga, Trentino, Italy, 70km
• Event 8: February 12, 2023 – Jizerská50, Bedrichov, Czech Republic, 50km
• Event 9: February 18, 2023 – Grönklitt Criterium, Orsa Grönklitt, Sweden, 50km
• Event 10: February 19, 2023 – Grönklitt ITT, Orsa Grönklitt, Sweden, 15km
• Event 11: March 5, 2023 – Vasaloppet, Sälen-Mora, Sweden, 90km
• Event 12: March 18, 2023 – Birkebeinerrennet, Rena-Lillehammer, Norway, 54km
• Event 13: April 1, 2023 – Reistadløpet, Setermoen-Bardufoss, Norway, 40km
• Event 14: April 2, 2023 – Summit 2 Senja, Bardufoss- Finnsnes, Norway, 67km

More information about the Ski Classics Pro Tour you can find at skiclassics.com.

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