Why do Athletes Carbo-Load?

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Nutrition Blog

Marathon runners, cyclists and swimmers tend to fill up on carbohydrates before a big competition. This stops their energy levels from plummeting during a race. However, not all carbohydrates are created equally which means that if you’re wanting sustained energy through your race you need to be eating carbs that give you sustained energy levels. Want to know more? Read this article to find out!

Why Carbo-load?


When athletes exercise, their bodies use glycogen. Glycogen molecules function as long-term energy storage. These are stored in the liver and muscle cells. However, this glycogen can be used up which results in a possible drop in performance as fatigue sets in.


Athletes carbo-load to prevent their bodies from running out of energy. During this process they top up their glycogen stores before an event.

During digestion, your body breaks down carbohydrates into sugar. The nature of this sugar depends on the foods which have been eaten. The sugar enters your bloodstream, where it is transferred to individual cells to provide energy.

Sugar is stored in your liver and muscles as glycogen which, as we’ve said before, is your energy source. The body uses carbohydrates to produce glucose which gives athletes the endurance they need to complete a race. It also improves their performance.

How much carbohydrates they consume corresponds with how much glycogen is stored in their bodies.

What can you eat?

Carbo-loading isn’t as simple as stuffing yourself with pasta. Many athletes’ performance is ruined with poor nutrition if they don’t eat the right carbohydrates.

There are two classifications of carbohydrates:

  • Complex carbohydrates like legumes, grains and starchy vegetables (potatoes, peas and corn).
  • Simple carbohydrates which are found mainly in fruits and milk, as well as in foods made with sugar, such as candy and other sweets.

Complex carbohydrates provide more sustained energy while simple carbs provide a spike in energy and then leave you feeling energy depleted.

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The Benefits of Carbo-loading

Experts say that under normal dietary circumstances, athletes have around 80 to 120 millimoles of stored glycogen per kilogram of body weight. Carbo-loaded athletes can have up to 200 millimoles per kilogram. This can improve their endurance by 2 to 3%.

Carbo-loading before a race can improve a runner’s endurance, speed, energy and alertness.

How does it work?

Before carbo-loading you have to deplete you glycogen stores. This tricks your body into thinking there’s something wrong with your glycogen stores. Your body then compensates by storing more when you carbo-load.

Athletes do this by eating a low-carb diet for three to four days, then carbo-loading for three to four days.


Other factors can influence the effectiveness of an athlete’s carbo-loading strategy, including:

  • How fit they are
  • How well they hydrate
  • And how intensely they exercise

When carbo-loading it’s best to consult a doctor, a registered dietitian or nutritionist because this practice can cause some discomfort or side effects. This includes digestive discomfort and blood sugar changes. To prevent digestive discomfort, experts recommend that athletes stay away from high-fibre foods one or two days before an event.

Despite carbo-loading, athletes still need to replenish their bodies’ energy during endurance events to maintain their blood sugar levels. They need to periodically consume sports drinks, gels, bars or fruit during their race. Athletes who experience blood sugar changes usually have to monitor their blood sugar levels during training. This way they can plan the correct meal plan.

Contact Trifocus Fitness Academy

If done correctly, carbo-loading can be the difference between an athlete winning or losing their event. Do it right and they experience endurance and performance benefits. Doing it wrong can potentially result in malnutrition.  Want to learn more about how nutrition affects athletic performance? Check out Trifocus Fitness Academy’s Athletic Nutrition Course to find out more!

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