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How to Fuel During the London Marathon

Written by James Fleming MSc, SENr

Fuelling the body is a bit like putting fuel in your car. If you add the wrong type of fuel, or worse, no fuel at all, then your performance will be severely affected. A bit like your car, during the run your ‘fuel tank’ will be draining away. We only have limited energy stores within the body (enough for roughly 90 minutes to 2 hours of exercise) so we need to make sure we keep it topped up to help complete the event itself.

Therefore, the purpose of this article is to provide you with advice around what you should eat and drink during the race itself.


Some runners like to run with hydration packs but on the course itself you will have access to a range of nutrition resources at regular intervals throughout the event.

Nutrition available on course:

  • Water is available every 2 miles in 250ml bottles

  • Energy drinks are available at miles 9, 15, 21 and 23 (note it will be in cups, not bottles)

  • Energy gels are available at miles 19 and 22

In your remaining training runs, I would recommend trying the products on offer on the course as they are sweeter than some of the girls or drinks you may have used previously and are not to every runner’s taste.


Providing you have consumed plenty of carbohydrate in the days leading up to the event itself, the muscle stores will be topped up ready for the start of the race.

On your way to the start line and holding pens, it would be beneficial to sip on water or sports drinks or maybe a small carb-based snack such as a gel, sports drink, or fruit such as a banana. At the start of any race, all runners are very nervous so once your race starts focus on getting into a good running rhythm and hitting your target pace for the rest of the course. As you are running, your ‘fuel tank’ will be starting to deplete so you need to think about nutrition sooner rather than later. A good guideline is to start fueling after about 30 minutes and then at regular intervals throughout the race.

It is recommended to consume around 30 to 60g carbohydrate per hour during prolonged exercise. There is further evidence to suggest higher amounts closer to 90g per hour however this is a lot to take in and can increase the risk of ‘runner’s gut’ if not practiced before during training. This is why it is so important to practice your race day nutrition during training where you start with small amounts and gradually increase it.


Carbohydrate is found in a whole range of food and drinks. Some examples of options that contain 30 grams of carbohydrate includes:

  • 500ml sports drinks

  • 1 large banana

  • 1.5 energy gels*

  • 1 x cereal bar*

  • A handful of jelly babies

  • 1 scoop of powdered carbohydrate mix

*Please be aware carbohydrate content between sports drinks, cereal bars and gels depending on brand.

After completing the first 30 minutes of the event, I would recommend starting taking on some fuel. It is up to you what you use but make sure you practice with it in training and then stick to it on race day. I have worked with several runners where they have mentioned that in previous events, they have tried different foods and as a result struggled to perform in their event.

The key to a successful nutrition strategy and successfully completing an event is to focus on consuming small amounts on a regular basis. If you were using gels on the day and trying to hit around 60g carbohydrate per hour, this would be the equivalent to consuming one energy gel every 20 minutes.

Some runners are happy to consume the same thing over the duration of the event but some runners experience food fatigue where they get fed up with the same thing. A simple way to help manage this is to mix up your snacks with different flavoured gels or swapping to other carbohydrate sources such as a handful of jelly babies.


In the previous article, I mentioned two: Caffeine and Nitrate.

As mentioned, caffeine takes around 60 minutes to be absorbed within the body and can be maintained for a few hours. Consuming caffeine during the latter stages of the marathon may help with sustaining your pace as caffeine helps reduced fatigue and perceptions of pain.

In terms of nitrate, as mentioned this takes around 2 to 3 hours for the body to digest and can last for up to 6 to 12 hours. There will be no need to consume additional nitrate during the marathon provided you have consumed your nitrate (1 to 2 shots of Beet It Sport Nitrate 400) 2 to 3 hours before the race as well as in the days leading up to the event for further enhanced benefits.


Staying hydrated during the race is just as important as consuming carbohydrate. Prolonged exercise can result in you becoming dehydrated which will start to make it harder to sustain your running splits and you will begin to slow down.

You can work out your sweat rate during your training runs using the following equation:

Body weight pre run (kg) – Body weight post run (kg)

Example: Record your weight in minimal clothing before completing your run. Once finished weigh yourself again in minimal clothing. If your weight has reduced by 1kg you know your sweat rate is around 1 litre per hour (1litre = 1kg). Please note sweat rate calculations are not 100% accurate but give you a much better idea of what is happening.


Practice your nutrition strategy for on the day during your training runs over the next few weeks so that you have time for your gut to adapt.

Depending on your finish time target you may be running for several hours and as a result trying to take more than 10 gels with you can be difficult to store and adds extra weight. Therefore, ask your friends, family, and any supporters you have coming on the day to hold onto extra drinks, gels and resources. That way you can pick some extras up if needed. When I ran the London Marathon last year, this worked very well for me.

In the next blog I shall discuss the nutrition recommendations for after the race itself.


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