Pre-event nutrition: How to fuel your body before a race

Whether you take on a running, cycling or trekking challenge, we're here to help you understand how to fuel your body in preparation for your big day.


The basics

The three compounds that the body converts into energy which allow us to move are fats, proteins and carbohydrates. Protein's main function is growth and tissue repair, and is only really used as energy when other sources are depleted, so its contribution to energy production in race conditions is relatively low. It is carbohydrates and fats which are the main sources of energy, with most energy produced by the metabolism of carbohydrates. The body uses these primarily and fats when their storage is depleted. For this reason carbohydrates should feature most in your pre-event nutrition.

There are two main types of carbohydrate: simple and complex. Simple carbs (sugars) such as glucose or fructose are quick sources of “fuel” for the body. Complex carbohydrates are more complicated compounds which take longer for the body to break down. A limited amount of carbohydrate can be stored in the muscles and liver in the form of glycogen. When muscle cells have a high demand for glucose, glycogen is broken down and when the demand is low, they absorb it from the bloodstream rebuilding the glycogen reserves.

One week to go

All your long training runs/cycles/treks are finished and it's time to take it easy. You won't hear "train less, eat more" very often but that's what you need to do to top up your glycogen storage. Depletion of glycogen levels is associated with muscle fatigue during prolonged exercise so the idea is to optimise and prolong your performance to avoid “hitting the wall”.

If you are training for an endurance event such as ironman or marathon, you need to start topping up your glycogen levels up at least a week before the event. If you are training for a sprint event such as 10K, 1-2 days may be sufficient. 

Easy-to-digest foods that will increase your glycogen levels include rice, tortillas, porridge, bread, pancakes, waffles, bagels, baked potatoes, yoghurt, and fruit juice. Watch out though, as many fruits are high in carbohydrates and fibre which can upset your stomach. Choose a low-fibre option like a banana or peel fruit such as apples, pears and peaches to reduced the fibre content. 

Your pre-event breakfast

The goal is to top up your glycogen stores which will have been depleted during your previous night’s sleep.

Your pre-event breakfast should be consumed 3-4 hours before to ensure the carbohydrates eaten have been both digested and absorbed. It should be rich in complex carbohydrates as they facilitate a gradual rise in blood glucose level and thus help to maintain steady energy levels for a longer period of time. Fat and protein metabolism takes longer than that of carbohydrates, plus they are not as effective as a source of energy during exercise and can remain in the stomach for longer which may cause discomfort. Keep the levels of fat and protein in your breakfast low. Fat can be used as an energy source towards the end of longer events; however, there is enough fat stored in your body so no need to consume extra fat before the event!

Great pre-event breakfast foods would be: porridge; cereals with low fat milk; banana; dried fruit; low fat yoghurt; rice pudding, baked beans on toast; toast with low fat jam, honey or marmalade; boiled eggs; lean grilled bacon and fruit juice.

Additionally, a light snack in the form of a cereal bar will be beneficial to competitors 1-2 hours before an event.

During your event

The most suitable form of carbohydrates to take on during an event are simple sugars in the form of a sports drink or gel. They provide a fast source of energy and help to decrease the glycogen to glucose conversion rate and hence provide energy for the latter stages. Most big events are well organised with water and sports gel stations along the way. We recommend you try gels before the day to avoid any unpleasant reactions or surprises!  


It is vital to keep hydrated during any event to keep all body functions working well. It is generally advised that 400-600ml of water should be consumed 3-4 hours before an event (together with your pre-event breakfast). This allows time to excrete any possible excess. Up to 300ml should be consumed 20 minutes before the start and you should drink regularly throughout to prevent dehydration.

Hope you've found our whistle-stop tour of pre-event nutrition helpful... to find out more about race/event nutrition, we recommend these articles:

How to carb load for marathon week

Carb loading diet

Carbohydrate Loading: 3 Effective Methods to Increase Your Chances of Marathon Success


Tomas Bittner
Osteopath  |  Sports Massage Therapist
The Rebalance Clinic 


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