🏃♀️ Key Takeaways
- Fuelling during your long runs helps prevent hitting the wall and improves endurance.
- Aim for 30g of carbohydrates per hour to start, gradually increasing towards 60g per hour or more with training.
- Choose from gels, chews, drinks or real food – whatever works for your gut.
- Electrolyte replacement is just as important as hydration, especially for runs over 90 minutes.
- Practice is key – training your gut to tolerate carbs and fluids is part of marathon prep.
Why Fuelling During Long Runs Matters
You might have heard of “hitting the wall” – that sudden, miserable moment when your legs turn to lead and your energy vanishes. This isn’t just psychological – it’s physiological. It happens when your muscle glycogen stores are depleted, leaving you running on fumes.
Long runs are designed to simulate marathon effort and duration, so practising your fuelling strategy here is essential. Proper fuelling helps you:
- Maintain energy and avoid crashing
- Train your gut to tolerate carbs during exercise
- Adapt your digestive system for race day conditions
By fuelling consistently on your long runs, you’re preparing both your body and brain for the demands of the marathon – especially the last 10km when nutrition makes or breaks performance.
How Many Carbs Do You Need During a Long Run?
Let’s break this down simply:
- 🥄 Start with 30g of carbs per hour if you’re new to fuelling during runs.
- ⏫ Train up to 60g or even 90g per hour if you’re aiming for a strong marathon finish.
- ⏱️ Consume something every 20–30 minutes to maintain a steady energy supply.
This approach mirrors professional sports nutrition guidelines and can significantly improve endurance by sparing glycogen (stored carbohydrate) and maintaining blood glucose (sugar aka carbohydrate) levels.
Here’s a handy table to visualise what 30g vs 60g of carbohydrates per hour looks like:
| Fuel Source | Approx. Carbs | Notes |
|---|---|---|
| 1 standard energy gel | 20–25g (some contain 40g) | Most common option, easy to carry |
| 1 large banana | 25–30g | Natural option, harder to digest on the move |
| 6 jelly babies | ~30g | Fast sugar hit |
| 500ml sports drink | 30–36g | Also helps with hydration and electrolytes |
| 1 pack of energy chews | 30–40g | Great for nibbling every 10–15 minutes |
💡 Top tip: Start by taking in 30g/hour for a few weeks, then gradually increase in 10–15g increments as your gut adapts.
What Should You Eat During Long Runs?
There’s no one-size-fits-all answer – what works for your running buddy might have you sprinting for the nearest bush. The key is to experiment during training, not on race day.
Popular Fuel Options:
- Energy gels – Easy to carry, fast-digesting.
- Energy chews – Great for nibbling during slower paces.
- Sports drinks – Combine carbs and hydration; look for ones with 30g+ carbs per 500ml.
- Real food – Small bits of banana, dried fruit, or even a mini sandwich work for some runners, though they’re often harder to digest.
The key is to build a routine and stick with it. Pick 2–3 products and rotate them to prevent flavour fatigue and gut upset.
What Should You Drink on Your Long Runs?
Hydration isn’t just about avoiding thirst – it’s about replacing what you’re losing through sweat. Especially on warm or humid Irish mornings, you’ll need to think about:
- Fluids – Aim for 400–800ml per hour depending on your sweat rate.
- Electrolytes – You lose sodium, potassium, and magnesium through sweat – water alone won’t cut it.
- Caffeine – A low dose can enhance endurance, but test it during training to avoid gut issues on race day.
Drink Options:
- Water + electrolyte tablet
- Carbohydrate + electrolyte sports drink
- Caffeinated energy gels – Many runners take one caffeinated gel half way for a mental lift. But, caffeine 30 minutes before the run is preferable.
🥤 Pro tip: If you’re using gels, sip water with them to aid absorption and avoid stomach issues. Or consume just prior to a water station.
Also, please mind your teeth. Good oral hygiene practices are super important before, after and in between races
Training the Gut to Tolerate More Fuel
You wouldn’t turn up to the start line without running long distances – so why expect your gut to magically tolerate 60g+ of carbs per hour?
Your gastrointestinal system can be trained, just like your legs. Here’s how:
Step-by-Step Gut Training:
- Start small – 30g/hour for your next 2–3 long runs.
- Increase gradually – Add 10–15g/hour every fortnight.
- Space your intake – Every 20 minutes, have a small portion (half a gel or a few chews).
- Monitor your symptoms – Note bloating, cramping, or GI distress.
If things go south (literally), reduce your intake slightly and try different formats (e.g., chews instead of gels, or drinks instead of solids).
Consider booking in with Sports Dietitians Orla or Aoife for more individualised adice by clicking here.
Fuelling Example for a 2–3 Hour Long Run
Here’s a realistic fuelling plan for someone aiming for 60g of carbs per hour on a 2.5-hour long run:
| Time | Fuel | Quantity | Carbs |
|---|---|---|---|
| Start | Water + electrolyte tab | 500ml | 0g |
| 30 min | Energy gel | 1 gel | 25g |
| 60 min | Energy chews | 3 pieces | 22g |
| 90 min | Sports drink | 500ml | 32g |
| 120 min | Caffeinated gel | 1 gel | 25g |
| 150 min | Chews or wine gums | ~5 pieces | 30g |
🎯 Total carbs: ~134g over 2.5 hours = ~54g/hour
Mix and match according to taste, gut tolerance and pace. You can drink more if it’s hot, or substitute some of the food-based carbs with drink-based ones if chewing during running is hard.
FAQs
How many carbs should I take during a marathon training run?
Start with 30g of carbs per hour and gradually train your gut to tolerate up to 60g–90g per hour. This range supports endurance and delays fatigue. Practise this during your long runs to find what works best for your body.
What are the best foods for fuelling long runs?
Energy gels, chews, and sports drinks are the most convenient. Bananas, dried fruit, or jellies can work too. Choose items that provide fast-digesting carbohydrates and that sit well in your stomach.
Can I use real food instead of gels?
Yes – some runners prefer real food like bananas or dates. However, they can be harder to carry and digest, so experiment during training. Always test real food options before race day.
Do I need electrolytes as well as carbs?
Yes, especially for runs over 90 minutes. Replacing sodium, potassium and magnesium lost through sweat helps maintain hydration and muscle function. Use sports drinks or electrolyte tablets.
What’s the best hydration strategy during long runs?
Aim for 400–800ml of fluid per hour, depending on temperature and your sweat rate. Use electrolyte drinks to stay hydrated and support performance.
Should I take caffeine during long runs?
Caffeine can reduce perceived effort and improve focus. If tolerated well, try one caffeinated gel or drink in the second half of your long run. It’ll take 30 minutes to hit your system so don’t wait too long or it’ll hit when showering afterwards! Test it in training before race day.
What’s the difference between 30g and 60g of carbs per hour?
30g/hour is a safe starting point. 60g/hour offers greater endurance benefits but requires gut training. Increasing carb intake slowly over time reduces the risk of GI distress.
Can I drink too much water?
Yes. Overhydration can cause hyponatraemia, which is dangerous. It is rare though. Stick to your thirst and include electrolytes to maintain fluid balance.
What if I get stomach cramps or GI distress?
Try different formats (e.g., chews or drinks), reduce fibre before your run, and space your intake into smaller amounts every 20–30 minutes. Build up tolerance slowly.
How do I train my gut to handle more carbs?
Start by taking 30g/hour, then gradually increase by 10–15g per week. Monitor how your stomach feels and adjust accordingly. The goal is to tolerate race-day fuelling without distress.
