You’ve taken the plunge and signed up for your first marathon. You’ve sorted your shoes, your gear, your watch and your training plan, and you feel ready to go. Then the questions start creeping in around marathon nutrition. What should you be eating, and more specifically, what do you need to eat during your runs?
I always found marathon training made me ravenous. As the mileage builds week by week, the hunger pangs tend to follow, and suddenly you feel like you could eat constantly. That increase in training volume does raise your energy needs, but it doesn’t automatically give you free rein to eat everything in sight, tempting as that may be. To train well and stay healthy, you need to eat mindfully so your body gets the nutrients it needs to support recovery, maintain energy levels and keep you marathon fit right through the training block.
In this post, we are going to talk about what to eat during the marathon. For advice on what to eat before and after a long run have a look at some of our other blog posts on this topic.
The Role of Glycogen
If you look up any information on exercise and energy you will come across glycogen. Glycogen is your body’s stored form of energy. When you eat carbohydrates, such as bread, rice, pasta or fruit, your body breaks them down into glucose. Any glucose that your body does not require straight away is stored in the form of glycogen, primarily in your muscles and liver.
Muscle glycogen is used by the muscles you’re working, which means your leg muscles rely heavily on these stores when you’re running. Liver glycogen helps keep your blood sugar levels stable, supplying glucose to your brain and working muscles during longer efforts. Together, these glycogen stores act like a fuel tank but as the miles add up, just as with your car the fuel tank level decreases and needs to be topped up. Unlike the empty tank of fuel which prevents a car from continuing, your body can access energy from fat, however this is slower to access and is less efficient means of energy.
This is generally when a runner feels like they have ‘hit the wall’. Energy levels have suddenly dropped, legs feel heavy and you just feel physically and mentally fatigued. This is why taking on nutrition mid run is essential and it is so important to find out what works best for you. Never, ever, leave this until marathon day to work out. This needs to be a huge part of your marathon training, get your marathon nutrition wrong and you either hit the wall or suffer awful Intestinal issues during the run. Getting it right can make crossing that finish line a lot more manageable.
How Much and How Often
On a full glycogen store, most runners can fuel around 90 minutes to two hours of running at a steady to moderately hard pace before those stores become significantly depleted. Exactly how long that lasts depends on several factors, including your pace, fitness level, body size and how efficiently your body uses fuel.
Even elite athletes need to replenish their stores mid run but their bodies are highly trained to maximize the efficiency of fuel storage and usage, enabling them to perform at incredibly high intensities for the duration of a marathon.
The guidelines for marathon nutrition usually state that 30 to 60 grams of carbohydrate per hour is required once you’re out on long runs. For many runners, especially those out on the course for longer than three hours, the upper end of this range (up toward 60–90 grams per hour) helps delay fatigue.
Carbohydrates should be your primary race fuel because:
Your body uses them fastest.
- They help maintain blood glucose levels.
- They reduce the risk of hitting the wall.
Protein isn’t a fuel during the race, it’s more for recovery after hard sessions and building muscle during your training cycle. Fats digest slowly and can make your stomach unhappy if eaten during running. Fibre is tricky on race day because it increases gut activity and can cause discomfort. Both fats and fibre are essential parts of your overall marathon nutrition but you’ll want to avoid them around and during your long runs.
Calculating How Much Carbohydrate is Required for Optimum Marathon Nutrition
A useful way to think about marathon fuelling is to split the race into two phases.
- First 3 hours: aim for 30–60 g of carbohydrate per hour
- After 3 hours: aim for 60–90 g of carbohydrate per hour
The reason for the increase is that glycogen stores are becoming more depleted after around three hours of running, and the risk of hitting the wall rises sharply if carbohydrate intake does not increase. Remember also that it takes about 20 minutes for ingested gels to convert into energy for your muscles. Therefore you need to be ahead of the game.
Below are example totals using mid-range targets that most runners can tolerate with practice.
| Marathon finish time | First 3 hours (30–60 g/hr) | After 3 hours (60–90 g/hr) | Total carbohydrate required | What this might look like |
|---|---|---|---|---|
| 4:00 hours | 50 g/hr × 3 hrs = 150 g | 70 g/hr × 1 hr = 70 g | ≈ 220 g | 1 gel every 30–35 minutes, then every 20–25 minutes in the final hour, supported by sports drink, 8-9 Gels total |
| 4:30 hours | 50 g/hr × 3 hrs = 150 g | 70 g/hr × 1.5 hrs = 105 g | ≈ 255 g | Gels every 30–35 minutes early on, increasing frequency after 3 hours, plus sports drink, 9-10 Gels total |
| 5:00 hours | 45 g/hr × 3 hrs = 135 g | 70 g/hr × 2 hrs = 140 g | ≈ 275 g | Gels every 35–40 minutes initially, then every 25–30 minutes after 3 hours, mixing gels, chews and sports drink, 7-8 Gels Total |
| 5:30 hours | 40 g/hr × 3 hrs = 120 g | 65–70 g/hr × 2.5 hrs = 160–175 g | ≈ 280–295 g | Conservative fueling early, then very regular intake after 3 hours using gels, chews, sports drink or simple sugars |
Important Points to Remember
- These are targets, not rules. Your gut tolerance matters more than perfection.
- Intake should increase after three hours because glycogen stores are running low and fatigue risk rises.
- This strategy must be practised during long runs so your digestive system adapts.
The goal is to arrive in the final miles with energy left to run, not just to survive. Fuel early, fuel consistently and give your body what it needs to carry you all the way to 26.2 miles (42k).
Types of In-Run Nutrition
| Type of nutrition | Examples | Advantages | Disadvantages |
|---|---|---|---|
| Energy gels | SIS, Maurten, High5, Precision, GU | Easy to carry, quick to consume, fast carbohydrate delivery, widely available on race courses | Can cause stomach upset for some runners, texture may be unpleasant, flavour fatigue, often need water to wash down |
| Liquid gels | Maurten Drink Mix, SIS Beta Fuel | Easier to digest for some runners, less thick in the mouth, combines fuel and hydration | Can feel heavy if overconsumed, harder to carry without bottles, taste may not suit everyone |
| Chews and gummies | Clif Bloks, High5 Chews, jelly-style sports sweets | Smaller doses allow steady intake, easier to pace carbs, more variety in texture and flavour | Require chewing which can be difficult at marathon effort, sticky in the mouth, slower to consume |
| Sports drinks | Lucozade Sport, Tailwind, isotonic drinks | Provide carbs, fluids and electrolytes together, easy to sip little and often, good for higher carb targets | Carb concentration varies, easy to underfuel if relying on course drinks only, can upset stomach if too strong |
| Sugary sweets | Jelly babies, gummy bears, wine gums | Cheap, familiar, easy to find, simple carbohydrates | Sticky, inconsistent carb amounts, less convenient to carry, may not sit well when running |
| Fruit | Banana, orange segments | Natural sugars, familiar food, provides some potassium | Contains fibre which may cause gut issues, bulky, slower digestion |
| Real food | PB&J sandwich, pretzels, flapjacks | Feels satisfying, can work well at slower paces, good for very long runs | Harder to chew and swallow, slower digestion, impractical for racing |
| Salt tablets / electrolytes | SaltStick, Precision Hydration tabs | Help replace sodium lost in sweat, may reduce cramp risk | Do not provide energy, unnecessary if already using electrolyte drinks or gels |
Hydration on the Go
Hydration is a huge piece of the puzzle. Fluids help transport nutrients to your muscles, keep your core temperature in check and prevent dehydration.
It is best to go with the little and often method, taking a few sips at every water stop rather than guzzling a large amount in one go. Alternating between water and a sports drink will also help keep electrolytes in check and replace any sodium lost in sweat.
Hydration isn’t just during the marathon either. Being well-hydrated throughout training and in the days before the race makes a big difference. Urine that’s pale yellow is a solid indicator that you’re hydrated. If it’s dark, you need more fluid.
Practice, Practice, Practice!
Every runner is different, and factors such as pace, gut tolerance, body size, experience and environmental conditions will all influence how much carbohydrate you can comfortably take on board. Use these numbers as a starting point, practice your strategy during long training runs, and adjust based on what works best for you.
As you can see there is a huge variety of gels, chews and options for your marathon nutrition, but if you start early in the plan testing various options your future marathon day self will be thankful.
Personally, I know I cannot tolerate more more than 4 gels before my gut starts to rebel. I take a mix of gels and sugary sweets such as jelly beans or cliff blocks. I find the gels unpleasant and require water to wash them down. They can also be difficult to open while running with the result that you open it too much and wear most of it or cannot get it open enough and throw most of it away. Practice makes perfect and possibly I did not do that enough!
The key is to test this all out before marathon day. Once your runs start adding up to 90 minutes it is time to introduce nutrition on the run. Keeping a log of what you consumed, when you consumed it, how you felt on the run and afterwards goes a long way at determining your best strategy for your marathon nutrition that will keep you going through to the finish line.
Putting it All Together
So, what have we learned here?
- The key point is you need to fuel your body during your long runs or you will risk ‘hitting the wall’.
- Your body stores enough energy for roughly 90 minutes of running
- You need to take on nutrition before you need it
- Practice what works best for you
- Do not leave it till race day to become acquainted with gels
- Check out your marathon aid stops as gels and sports drinks are often offered at certain points along the way (if they don’t offer the gels you like, bring your own)
- Nothing New on Race Day!
- Hydrate – little and often
- Know what your gut will tolerate
- Have your Marathon Day Nutrition figured out at least 4 weeks before race day and rehearse on each long run leading up to the big day.
Ultimately, marathon nutrition is about preparation and personal experimentation rather than finding a single perfect product or plan. The goal is to keep your energy levels steady from the early miles right through to the finish, while avoiding stomach issues that can derail an otherwise strong run. By understanding how your body uses glycogen, practising fuelling and hydration during long runs, and keeping notes on what works and what does not, you arrive on race day with confidence rather than guesswork. Use the guidance and tables as a starting point, test your strategy well before the marathon, and trust the process so your nutrition supports your training and carries you through all 26.2 miles (42K) feeling as strong as possible.
If you want clear guidance, realistic training and help getting your nutrition right, Achieve Running Club is here to support you every step of the way. Join the club and keep making progress.
To learn what to eat before and after your long runs, have a look at our other blog posts.
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