How Much Carbohydrate Do Endurance Athletes Need During Exercise?

Endurance athletes are often told to consume more carbohydrate, but the right amount depends on the session.

A short recovery run does not require the same fuelling strategy as a long ride, marathon or Ironman. The goal is not simply to consume as much carbohydrate as possible, but to match intake to the duration, intensity and demands of the session.

Why do carbohydrates matter for endurance performance?

Carbohydrates are an important source of energy during moderate- and high-intensity endurance exercise.

The body stores carbohydrate as glycogen in the muscles and liver. However, these stores are limited. As exercise continues, carbohydrate availability can decrease, making it more difficult to maintain your intended intensity.

Consuming carbohydrate during prolonged exercise can help maintain blood glucose, reduce reliance on stored glycogen and support carbohydrate oxidation. Together, these effects may help athletes sustain their pace or power for longer and delay fatigue. Without it, stores become depleted, blood glucose falls, and fatigue increases.

Carbohydrate also has a role beyond providing energy directly to the working muscles. During shorter, high-intensity exercise, even small amounts of carbohydrate in the mouth may influence the central nervous system and support performance.

This does not mean that every training session requires aggressive fuelling.

An easy 40-minute recovery run has very different demands from a three-hour ride, marathon-specific long run or Ironman race. Your carbohydrate strategy should therefore follow the principle:

Fuel for the work required.

How much carbohydrate do you need during endurance exercise?

Carbohydrate requirements depend on several factors, including:

• The duration and intensity of exercise

• Your body size and training status

• The sport or activity

• Your performance goals

• Your opportunities to eat or drink

• Your gastrointestinal tolerance

• The conditions in which you are training or competing

  
  

General starting points are shown below.

Exercise duration	General carbohydrate target (in grams per hour (g/h))
<1 hour	Usually not required Small amounts (~30g/h) or a carbohydrate mouth rinse may help during high-intensity sessions
1-2 hours moderate	30-60g/h
1-2h hard/race-like	60-90g/h
2-3h endurance event	60-90g/h, generally using a mixture of glucose and fructose
2-3h high-demand race or 3+h prolonged race	Some trained athletes may work towards approximately 90-120 g per hour

Traditional guidelines have recommended 30-60 g per hour for longer exercise and up to approximately 90 g per hour during events lasting more than 2.5 hours. At higher intakes, combining carbohydrate sources such as glucose and fructose can improve absorption and oxidation compared with relying on one carbohydrate source alone.

More recent research suggests that approximately 90-120 g per hour may represent a practical upper range for many athletes attempting very high carbohydrate intakes. However, this is not a universal target, and more carbohydrate is not automatically better. These amounts are most relevant to selected athletes completing long or demanding events who have progressively trained their gut to tolerate them.

The sport also matters

It may be easier to consume and tolerate carbohydrate while cycling than while running.

Running involves repeated impact, fewer convenient opportunities to eat and a greater likelihood of gastrointestinal discomfort.

The best target on paper is not necessarily the best target for the individual athlete.

Your plan must also be realistic enough to execute while moving at race intensity. If increasing your carbohydrate intake causes bloating, nausea, reflux or an urgent need to use the toilet, the issue may not simply be the total number of grams.

Read our guide to gastrointestinal symptoms and gut training during endurance exercise.

Practical Guidelines

Don't wait until it is too late to start fuelling during a key training session or race. Instead:

• Start consuming carbohydrate early during longer sessions

• Spread intake throughout the hour

• Combine drinks, gels, chews and foods where appropriate

• Match fuelling to the demands of the session

• Practise the strategy before competition

• Avoid copying another athlete’s intake without considering your own needs

References

Burke, L. M., Hawley, J. A., Wong, S. H., & Jeukendrup, A. E. (2011). Carbohydrates for training and competition. Journal of sports sciences, 29(sup1), S17-S27.

Morton, J. P., Fell, J. M., Gonzalez, J. T., Hearris, M. A., Podlogar, T., Pugh, J. N., & Wallis, G. A. (2026). From Metabolism to Medals: Contemporary Perspectives and Revisiting Carbohydrate Guidelines for Fuelling Endurance Athletes During Exercise. The Journal of nutrition, 101442.

Naderi, A., Gobbi, N., Ali, A., Berjisian, E., Hamidvand, A., Forbes, S. C., ... & Saunders, B. (2023). Carbohydrates and endurance exercise: a narrative review of a food first approach. Nutrients, 15(6), 1367.

Plews, D. J., Booth, P. D., Krieger, T., & Maunder, E. (2026). Fuelled or Fooled? Examining the Evidence and Mechanisms Behind Ultra-High Carbohydrate Intake in Endurance Athletes. Sports Medicine, 1-22.