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Science of Carbohydrate Loading for Running

What is carbohydrate loading and why should you do it?

Carbohydrate loading is the process of maximising your muscle and liver glycogen stores by consuming a large quantity of carbohydrate before endurance exercise. Consuming such a large amount of carbohydrate will increase body mass; which could be concerning for runners, however the benefits of greater glycogen stores appear to outweigh the negatives of greater body mass as carbohydrate loading is shown to improve endurance running performance[1,2]. Your body has a limited capacity to store glycogen and it will be broken down and utilised as fuel during high intensity exercise, therefore to optimise performance it is important to maximise your glycogen stores, particularly before competition.


When and how should you load carbohydrate?

Carbohydrate loading should take place the day before an endurance event that lasts longer than 90 minutes[3]. One day of carbohydrate loading is shown to be as effective as three days of loading[4]. For optimal glycogen storage the day before the event you should aim to consume 3.6-4.6 grams per pound of body mass (8-10 grams per kilogram of body mass) of primarily high glycemic index (GI) carbohydrate on this day[5]. Ingestion of high GI carbohydrates such as rice, bread, pasta and cereals appears to result in greater glycogen storage than low GI carbohydrates[6] due to being rapidly digested and absorbed. For example an individual weighing 154 lbs (70 kg) should aim to consume 560-700 grams of carbohydrate the day before an event. Ideally this quantity of carbohydrate should be consumed at evenly dispersed periods throughout the day, i.e. every 2-3 hours. Fat content should be kept relatively low in order to aid digestion of carbohydrate. For an example carbohydrate loading day see the table below.


Time of Day Food (grams of carbohydrate)
Breakfast 100g low fibre breakfast cereal with milk (90g)
1 medium banana (20g)
300ml orange juice (26g)
Morning snack 1 serving of GO Electrolyte (36g)
1 average pot of low fat fruit yoghurt (16g)
50g raisins (35g)
Oats and honey snack bar (27g)
Lunch Ham salad sandwich with butter (4 slices of white bread) (66g)
Afternoon snack 1 serving of GO Electrolyte (36g)
1 GO Energy bar (44g)
1 medium banana (20g)
Dinner Spaghetti Bolognese (250g white pasta, 150g tomato & basil sauce, 85g turkey mince) (97g)
3 slices of garlic bread (32g)
Evening snack 1 white bagel with jam (55g)
40g porridge oats with 1 tablespoon of honey (20g)

Total calories: 3570 kcal
Carbohydrate: 620g
Protein: 120g
Fat: 70g





  1. Brewer, J. C., Williams, C., & Patton, A. (1988). The influence of high carbohydrate diets on endurance running performance. European Journal of Applied Physiology and Occupational Physiology, 57(6), 698-706
  2. Karlsson, J., & Saltin, B. (1971). Diet, muscle glycogen, and endurance performance. Journal of applied physiology, 31(2), 203-206
  3. Hawley, J. A., Schabort, E. J., Noakes, T. D., & Dennis, S. C. (1997). Carbohydrate-loading and exercise performance: an update. Sports Medicine, 24(2), 73-81
  4. Bussau, V. A., Fairchild, T. J., Rao, A., Steele, P.,&  Fournier, P. A. (2002). Carbohydrate loading in human muscle: an improved 1 day protocol. European Journal of Applied Physiology, 87(3), 290-295
  5. Burke, L. M., Hawley, J. A., Wong, S. H. S., & Jeukendrup, A. E. (2011). Carbohydrates for training and competition. Journal of Sport Sciences, 29(sup1), S17-S27
  6. Wee, S. L., Williams, C., Tsintzas, K., & Boobis, L. (2005). Ingestion of a high-glycemic index meal increases muscle glycogen storage at rest but augments its utilization during subsequent exercise. Journal of Applied Physiology, 99(2), 707-714
Written By

Ted Munson (Performance Nutritionist)

Ted is a Performance Nutritionist here at Science in Sport.