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What is Carbo Loading and Is It Effective?


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Carbohydrate or ‘carbo’ loading is probably the oldest nutritional strategy endurance athletes use to improve performance. In a previous post we mentioned that eating a high carbohydrate diet is the most common method athletes use to achieve faster race times. You can read that post here. Today I want to talk about carbo loading, which is also called glycogen loading. If you like you can watch this in a video on my YouTube channel.

What is Cabo Loading?

Carbo loading is a process where you supercompensate your muscles and liver with glycogen (the storage form of carbohydrate) by eating extra carbohydrate in the days leading up to an endurance event.

By topping off your tank (muscles and liver) with carbohydrate you can exercise more intensely and for a longer duration.

Let’s take a closer look at the history of carbo loading and provide some recommendations.

Carbo Loading: The First Nutritional Strategy


Back in the mid-60’s, a pioneer in the field of exercise physiology named Per-Olf Astrand developed a regimen that allowed runners to store maximum amounts of glycogen. His plan instructed athletes to severely deplete their carb stores through very exhaustive training 7 days prior to competition. The next 3 days were spent restricting carb intake by increasing dietary fat and protein.

With three days remaining before competition, athletes would consume a carb-rich diet. This regimen was shown to increase muscle glycogen stores to over twice their normal levels. Thus the term ‘supercompensation.’

Modern Methods for Carbo Loading

In the early 80’s a newer model was developed by Sherman, which eliminated the carb depletion phase and low carb intake suggested by Astrand. Instead athletes were recommended to continue eating a normal diet (~55% carbs) while reducing (tapering) their training time and intensity. Three days before the event athletes ate slightly more carbs.

This regimen can be scary because the additional carbohydrate adds 1-3 pounds of water weight. More specifically, with every ounce of glycogen the body stores 3 ounces of water. For this reason, carbo loading helps maintain hydration and can be good for endurance athletes competing in longer events like a triathlon, marathon, or ultramarathon.

Can You Carbo Load in 24-hours?

The short answer is YES!  Research within the last decade suggests you can maximize glycogen stores with a 1-day protocol. Using this plan, eat normally until 24 hours before your event. Then replace 200-500 fat and protein calories with carbohydrate the day before your event. Eat a small high carb snack/meal for breakfast and you are good to go!

The day before competition your biggest carb meal should be either breakfast or lunch. See what works best for you. Consume a smaller dinner with normal amounts of carbohydrate.

Does Carbo Loading Always Translate to Improved Performance?

No it doesn’t. There are many factors involved in having a great race. You can fuel well but performances may suffer due to factors like lack of mental toughness, poor training leading up to the event, or maybe you went into the race injured.

Ok, let’s talk pre-race pasta parties. Carbo loading parties are popular but truthfully there is NO need to glycogen load for a 5K! There….I said it!   It provides NO benefit at all. I understand it is a social activity and an additional revenue stream for the organizers. Unless your event takes longer than 2 hours to complete, it is simply a waste of time. Truthfully your performance may suffer. I hear racers complaining at the finish line wondering why they didn’t perform well in their 5k race. There is a good chance over consuming carbs the night before was the issue.

What is your experience with carbo loading? Leave a comment and let me know.

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