If you’ve trained for a marathon, you’ll know that fitness alone isn’t always enough. Somewhere in the final third of the race, the body starts asking harder questions: Can I hold this pace? Why does this suddenly feel so difficult?
Much of that experience comes down to fuel availability, particularly carbohydrates.
This article looks at how marathon fuelling works, why carbohydrate intake matters, and how energy gels including real-food based options like Purendure fit into a practical marathon nutrition strategy.
What Happens to Your Energy During a Marathon
At marathon pace, your body is working aerobically, using a mix of fat and carbohydrates to produce energy. While fat stores are large, fat alone can’t support faster running speeds. As pace increases, your body leans more heavily on carbohydrates.
The challenge is that muscle glycogen stores are limited. For most runners, they begin to run low after 90 minutes of sustained effort. As this happens, you might notice:
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Your pace feels harder to maintain
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Effort rises even if speed stays the same
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Concentration slips
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Small discomforts feel much bigger
This isn’t a lack of willpower it’s physiology.
Why Runners Fuel During a Marathon
Taking in carbohydrates during the race helps in a few important ways:
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It supports blood glucose, helping both muscles and the brain
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It slows the rate at which glycogen is depleted
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It helps maintain a steady energy output over time
This is why marathon fuelling is usually proactive. Waiting until you feel exhausted is often too late to fully recover.
How Much Carbohydrate Do You Actually Need?
You’ll often see general recommendations of 60-90 grams of carbohydrate per hour for long-distance running. Some runners can tolerate more, but higher intakes usually require practice and gut training.
What works best depends on:
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Your pace and race duration
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Body size and training background
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How well your stomach tolerates fuel while running
The key takeaway is that fuelling is individual, and your long runs are where you learn what suits you.
Why Energy Gels Are So Common in Marathons
Energy gels are popular because they make fuelling manageable while moving. They’re easy to carry, quick to consume, and provide a known amount of carbohydrate.
That said, not all gels feel the same when you’re 30 km into a marathon. Texture, sweetness, and ingredient choice can all affect how a gel is tolerated, especially when digestion is already under strain.
Ingredient Simplicity and Gut Comfort
During a marathon, blood flow is directed toward working muscles, not the digestive system. This means digestion slows, and the gut becomes more sensitive.
Some runners find that simpler, familiar ingredients are easier to tolerate under these conditions. Real-fruit based gels, such as Purendure®, use fruit-derived carbohydrates and minimal ingredients, which some runners prefer for their texture and taste. As always, tolerance varies, and testing in training is essential.
Practicing Fuelling in Training
Fuelling isn’t something to “figure out on race day.” Long runs give you the chance to:
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Practice taking fuel at marathon pace
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Learn how often you prefer to fuel
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Notice how your stomach responds under fatigue
Many runners aim to take fuel every 20-30 minutes, keeping intake steady rather than taking large amounts all at once.
Race Day: Keeping It Simple
On race day, most runners aim to:
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Start fuelling early, before energy dips
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Stick to what’s been practiced in training
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Take gels with water when possible
Late in the race, when fatigue sets in, familiar flavours and textures can make a real difference to whether fuelling stays manageable.
Clean Sport Considerations
For runners competing in organised events, supplement choice can carry extra responsibility. Products certified by Informed Sport have been tested for a wide range of substances prohibited in sport using ISO 17025 accredited methods, offering additional assurance around contamination risk.
This doesn’t change how a gel fuels the body, but it can matter for peace of mind.
Finding What Works for You
There’s no perfect fuelling strategy that suits every runner. The most effective approach is usually the one that:
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Fits your pace and race plan
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Sits well with your stomach
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Has been tested repeatedly in training
Fuelling is part of the marathon learning curve. The more you practice it, the less it becomes something you have to think about on race day.
Final Thoughts
Marathon fuelling is ultimately about supporting your body as it works hard over a long period of time. Understanding how carbohydrates fit into that picture can make fuelling feel less confusing and more intentional.
Energy gels are simply a tool and like any tool, they work best when you’ve learned how to use them in a way that suits you.
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