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Carbohydrate Loading

Endurance athletes, e.g. marathon runners, rely on their stores of glycogen as a source of energy during competition. Carbohydrate loading is a legal method of boosting the amount of glycogen in the body prior to a competition. The information provided is from personal experience in following the process in preparation for a number of marathons.

What is the process?

Six days prior to a competition, the process begins.

  • For the first three days, the athlete consumes minimal carbohydrate and exercises so as to deplete the bodies glycogen stores
  • In the last three days, the athlete consumes primarily carbohydrate and reduces the training load

So, what is the theory?

At the end of day three, the body will think that there is a problem with its glycogen stores and that it should store more glycogen than normal.

In the last three days, when the athlete consumes carbohydrate, the body will replenish the glycogen stores and top them up with a little bit extra.


In the first three days, ensure adequate carbohydrates (about 60grm per day) are consumed to maintain the functioning of several important systems in the body.

In the last three days the diet should be primarily carbohydrate, do not overeat, but you do need to consume adequate protein, minerals, vitamins and fluid.

You will find that you will need to consume larger amounts of fluid than normal. Monitor your urine, it should be clear, to ensure you are drinking sufficiently.

If you decide to try carbohydrate loading, then try it in stages during your training. Start with depletion, low carbohydrate diet for one day, high carbohydrate diet. If no adverse effects, then extend the period of the low carbohydrate diet to a maximum of three days. Keep a detailed log of what you do and what happens.

Horwill (1996)[1] suggests that serve depletion is no longer necessary. If carbohydrate is increased and training reduced by two-thirds during the week before competition muscle glycogen will be increased without any of the above discomforts.

Sheridian (2015)[2] suggests you consume low fibre, easy digested carbohydrate e.g. fruit and vegetables (remove skin and seeds), white bread, white pasta, white rice, honey, jelly and refined cornflakes like cornflakes.

The bad news

Some potential side effects are:

  • Muscle stiffness
  • Diarrhoea
  • Chest Pain
  • Depression
  • Lethargy



  1. HORWILL, F. (1996) Twelve things you should know about carbohydrates. Athletics Coach, 30 (2), p. 14-15
  2. SHERIDAN, H. (2015) Loaded and Ready, Athletics Weekly, 23rd April, p. 60

Related References

The following references provide additional information on this topic:

  • BOSCH, A. et al. (1993) Influence of carbohydrate loading on fuel substrate turnover and oxidation during prolonged exercise. Journal of Applied Physiology, 74, p. 1921-1921
  • BUSSAU, V. et al. (2002) Carbohydrate loading in human muscle: an improved 1-day protocol. European journal of applied physiology, 87 (3), p. 290-295
  • HAWLEY, J. et al. (1997) Carbohydrate-loading and exercise performance. Sports Medicine, 24 (2), p. 73-81

Page Reference

If you quote information from this page in your work, then the reference for this page is:

  • MACKENZIE, B. (2001) Carbohydrate Loading [WWW] Available from: [Accessed

Related Pages

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