Why a diet rich in carbohydrate is essential for sports nutrition

How the body makes energy

The body uses energy in the form of something called adenosine triphosphate, or ATP for short. ATP is the primary currency of energy for high-intensity and intermittent sports as it is “quick-release”, but is also relied upon in endurance activities. Your body has very limited stores of ATP (only about 1500 calories worth in total) so it must be regenerated.

Carbohydrate is important for ATP production and is therefore an indispensible source of fuel for an athlete. There are various factors that affect fuel use, such as the intensity and duration of the sport; whether there is an opportunity for replenishment of glucose; training adaptation; and the level of glycogen stores.

Your body can produce ATP from carbohydrate, although only in small amounts (approximately 2-3mins of activity before fatigue), via a rapid metabolic pathway. This is essential for high-intensity exercise when the rate of ATP production is important. This is in contrast to other energy systems which can produce large amounts of energy but much more slowly. These slower pathways are used more in low intensity exercise.

The primary carbohydrate we are talking about when we talk about energy metabolism is glucose. Most of the carbs you eat like bread, potatoes, pasta etc. are broken down into this simple sugar which can then be used by the body to make energy. Glucose is stored as glycogen in the muscles and liver, and a small amount remains in in your blood circulation, and glycogen is the starting point for producing this quick-release ATP. These stores are limited so an adequate intake of carbohydrate is necessary to maximise and replenish them.

Maximising your glycogen reserves

Maximising your glycogen stores is absolutely essential to achieving optimum athletic performance.

Stores should be replenished during training and competition if the sport allows.

If glycogen stores are not replenished after training, initial levels will be too low at the start of the next session. There are several factors affecting replenishment. The time it will take to replenish stores will vary on the amount of activity. It can take up to two days post-training and up to seven days after a marathon.

There are practicalities of a high carb diet to consider, however. A significant amount of carbohydrate is needed but it is important not to gain weight. Therefore the fat in the diet should be reduced. A high carbohydrate diet can be bland and unpalatable, and it can be filling so difficult to eat a lot.

The views expressed in this article are those of the author. All articles published on Nutritionist Resource are reviewed by our editorial team.

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London W1G & EC1V
Written by Jo Travers, BSc RD (The London Nutritionist)
London W1G & EC1V

Jo Travers, The London Nutritionist and author of The Low-Fad Diet, is a state Registered Dietitian with a First Class BSc (Hons) in Human Nutrition & Dietetics. She has been in private practice for ten years, She has carried out over 1500 hours of one-to-one consultations with more than 600 cli...


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