Energy Guide for Marathon

Are you one of the many thousands signed up for a Marathon in 2025? Then you are probably already well underway with your marathon training. But something many people overlook is the importance of energy and fluid intake – and starting with it early in training.

A well-planned energy strategy helps you not only on race day itself, but also during your long training sessions, where you can optimize your performance and recovery.

You can find all PurePower products for running here!

Why is energy important during a marathon?

During a marathon, you will burn a lot of energy, primarily from carbohydrates. However, the body only has limited glycogen stores, which typically last for approx. 90 minutes at high intensity. If you do not top up your stores along the way, you risk hitting “the wall,” where your energy runs out and your pace drops drastically. By consuming carbohydrates along the way, you can keep your energy level stable and perform your best all the way to the finish line.

In addition, fluid intake is crucial for your performance. Even a small degree of dehydration can lead to reduced performance, an increased heart rate and greater strain on the body. During a marathon, you lose fluid through sweat, and if you do not replace it continuously, it can result in fatigue, cramps and dizziness. Therefore, make sure to drink regularly along the way, either from the aid stations on the route or by bringing your own fluid in a softbottle.

How to get started in training

Carbohydrate: 

We recommend that during your training you start by consuming 20-30 g of carbohydrate per hour, which corresponds to approx. 1 gel or 1 bag of chews. This way, your stomach gradually gets used to absorbing carbohydrates, and you avoid stomach issues. The goal should be to build up to 30-60 g of carbohydrate per hour, corresponding to 2-3 gels per hour for your marathon. So if you have training runs of + 1 hour, remember to bring energy with you for training. Also remember to start early. If, for example, you are going to run for 2 hours, it is too late to only take something after 1.5 hours when you begin to feel tired. Timing your energy intake is something you need to test, but we recommend starting around 30 minutes and then consuming something continuously every 30 minutes. It may also be easier for you to think in km, so find out whether it should be after every 5 km or something else.

Options for carbohydrate intake:

• Energy Gels – Fast-absorbing carbohydrates, easy to consume.
• Energy Chews – A bag with 12 gummies that provide fast-absorbing energy
• Carbo Race Electrolyte – Combination of fluid, electrolytes and carbohydrate.

Fluid and salt

The body can absorb up to 1 liter of fluid per hour, but most people should aim for an intake of 0.5-1 liter per hour during a marathon. During the race itself, this will primarily happen by drinking at the aid stations, as very few people bring their own fluid – but it can be an option if you prefer it.

It is important to train fluid intake during your long training sessions, as for many people it can feel uncomfortable to drink a larger amount of fluid that bounces around in the stomach. Therefore, it is an advantage to distribute your fluid intake into smaller portions along the way.

When you train, there are of course no aid stations, so here you can practice by carrying a softbottle in your hand or using a hydration vest. This way, your body gets used to absorbing fluid continuously, which can make a big difference on race day. You can find the PurePower softbottle here 

If you find that you sweat a lot or it is very hot when you run, you may want to consider taking salt capsules along the way to avoid dehydration and maintain a good salt balance. 

Energy guide for the Copenhagen Marathon

Now you have trained with both energy and fluid during your training sessions and are ready to make an energy plan that will help you safely through your marathon. Here are our recommendations for what you should focus on – from the day before the race, to during the race and to your recovery after the finish line – so you can have the best experience and perform optimally. We have used the Copenhagen Marathon as the basis in terms of aid stations, but these can simply be adapted to the marathon you are participating in. 

 

The day before the race – prepare your body for performance 🏃♂️💨 

To give your body the best conditions for a marathon, it is important to focus on both energy and fluid:

Fill up your stores – Increase your carbohydrate intake (carboloading) to maximize your glycogen stores, so you have energy for the entire distance. This does not mean you should overdo sugary foods. Instead, focus on eating a larger amount of carbohydrates with your meals. You can also consider several good carbohydrate-rich snacks or small meals. Aim for your diet to consist of 60-70% carbohydrate, preferably from sources such as rice, pasta, oats, bread and similar foods.

Choose easily digestible meals – Eat food that is easy to digest, and avoid heavy or very high-fiber foods that can cause stomach discomfort on race day.

Fluid balance – Make sure to drink plenty of fluid and get enough salt, so you start the race well hydrated. However, avoid overdoing your fluid intake, as it can lead to unnecessary fluid retention.

 

Morning before the race – make sure you have the right preparation

Eat your breakfast approx. 3-4 hours before the start of the race. This meal should primarily consist of carbohydrates and be easy to digest, so you have time to digest it before the start. Choose something you are used to eating and running on – something that gives you stable energy without causing stomach issues. Feel free to drink 0.5 liters of water with the meal and consider adding an electrolyte tablet if it is going to be hot. Find electrolytes here 

After the meal, you should only sip a little fluid up until the start, and stop drinking 1 hour before the start. This will help you avoid having to pee during the race, so you are ready to go all out from the start! 

Eat a light, carbohydrate-rich snack 30-90 minutes before the start – for example an energy bar, a banana or a white roll with honey. If you are the type who does not want to eat right before the start, you can take a small amount of sports drink or a gel.

During your marathon – keep your energy up 

During the marathon, the most important thing is to maintain the body’s fluid balance.  This is because dehydration will have a far greater effect on your performance than hitting the wall, as dehydration can cause you to stop completely, while the wall only results in a slower pace. Therefore, it is important to drink continuously and make a strategy for fluid intake. You should drink regularly and preferably 0.5-0.8 L per hour. Therefore, make sure to stop at every aid station – do not wait until it is too late. The good thing about the big marathon races is that you often come to an aid station. At the marathon in Copenhagen, you encounter an aid station almost every 3 km. So if you happen to miss one, fortunately it is not far to the next aid station.

Aim to consume 30-60 g of carbohydrate per hour. A typical gel contains 20-23 g of carbohydrate. Remember not to start consuming more energy than you are used to handling. Stick to the amount you have trained with during training. But also follow your plan consistently throughout the entire race to ensure that you have the necessary energy and fluid to reach the finish line.

If it is hot, or if you sweat a lot during the race, it can be an advantage to add a little extra salt to your fluid strategy. When you sweat a lot, you lose not only fluid, but also electrolytes, especially sodium, which can negatively affect your performance and increase the risk of cramps. 

To avoid this, you can bring salt capsules and take one capsule per hour during the race, especially if you notice that you are sweating a lot or running in hot conditions. Salt helps maintain fluid balance and support muscle function, which can help keep you on track throughout the entire marathon.

Remember that it is important to find the right balance – you do not want to overdo your salt intake, but if the conditions require it, including it in your strategy can give you an advantage.

 

After the marathon – focus on recovery through nutrition

Once you have completed the marathon, it is important to focus on replenishing both fluid and energy stores to optimize recovery. After a hard race, you are probably slightly dehydrated, and your glycogen stores are depleted, so the body needs quick energy and fluid to recover.

Make sure to get something carbohydrate-rich and quickly digestible within the first 30 minutes after the race. This helps replenish the empty glycogen stores. Choose light meals such as an energy bar, a banana or a smoothie that can quickly give the body the necessary energy. Feel free to drink a sports drink or water to restore fluid balance.

A good main meal should be eaten around 1-2 hours after finishing. Make sure it contains both carbohydrates and protein, which helps rebuild muscle tissue and refill glycogen stores. 

 

Here you get an example of an energy and fluid plan for the Copenhagen Marathon. Fluid is planned according to aid stations, and energy and salt intake according to the distance you have run. This is only an example, and we recommend that you try to make your own plan adapted to your needs and your marathon’s aid stations. It may also make more sense for you to plan energy intake according to time.

Is this your first marathon? Read our blog post Get through your first marathon written by PurePower ambassador Jonas Manley