Energy intake during running is crucial, especially for long distances. Much has been written and researched on this topic. How far should I run before taking carbs? How much should I take? How often? In what form? Will this upset my stomach?
Questions abound.
Most agree that consuming some carbs is best when running long distances.
Many believe that taking carbs is key to avoiding hitting the wall during a marathon. However, too many carbs too quickly can cause stomach issues, which is undesirable during a marathon.
Why do we need carbs at all?
While running, we burn both fat and carbs to get energy for muscles. At higher speeds, more energy comes from carb burning. Thus, having carbs available is vital for peak performance.
The body converts carbs into glucose stored in muscles and liver. Most people can store around 500-600 grams of glucose in muscle and liver glycogen stores. Additionally, glucose is available in our bloodstream—known as blood sugar—which changes faster than our glycogen stores.
We could delve deeper, but I’ll move on to the questions posed at the start.
How far should I run before taking carbs? And how much?
We all differ in tolerance and carb-burning rates. However, general guidelines are helpful for most:
- Activities under 45 minutes: No need for carbs
- 45-75 minutes: Some water and carbs (1 gel or similar)
- 1-2 hours: 30g carbs per hour.
- 2-3 hours: 60g carbs per hour.
- Over 3 hours: 90g carbs per hour.
Swedish energy producer Maurten, sponsor of top runners and cyclists like Eliud Kipchoge and Team Jumbo Visma, offers less conservative energy intake advice.
Maurten suggests:
- Under 1 hour: 40g carbs shortly before start
- 1-2 hours: 80g total. 40g before start, 40g during
- Over 2 hours: 80g carbs per hour.
(Spread intake to avoid stomach issues.)
There’s no consensus on how much to take. Test products in training to see what your stomach tolerates. For high carb intake, use isomaltulose or a 2:1 glucose-fructose mix (e.g., Maurten or High-5 Slow Release). Research shows these forms are gentler on the stomach. If sticking to general guidelines, the mix is less critical.
When running in hotter conditions than the ideal 16-18°C, reduce carb intake. Heat makes carb absorption harder, risking stomach issues on a hot day.
Despite these considerations, one thing is clear: Carbs are crucial during activity. A 2019 Brazilian study showed that carb intake during exercise improves performance more than pre-exercise meals. The best-performing group ate breakfast and consumed carbs during exercise.
The last question was about stomach issues. No guarantees, but following guidelines, practicing before events, and spreading intake should keep you on the safe side. Remember, carbs help reach your goal on long distances, but too much too fast can cause problems.
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