Fuel your marathon

The importance of carbohydrates to marathon runners

Carbo-loading is vital to long-distance runners, especially those intending on running a marathon. Carbs provide energy which is slowly released during the course of a run, so stocking up on them is a must.


Fuelling up on carbohydrates is crucial to your chances of marathon success. Ideally for the runner, the training diet should consist of:

  • 60 per cent of energy from carbohydrates
  • 20 to 30 per cent from fat
  • 10 to 20 per cent from protein

Why carbs for running?

Carbohydrates are broken down in the body and stored in the muscles and the liver as glycogen. Glycogen is broken down into glucose and is used to fuel the early and later stages of exercise, and during high intensity activities.

If your regular diet while training is low in carbohydrates and you are involved in running for over an hour each day, then your glycogen stores will deplete over time. This may cause you to feel more tired and incapable of training at the level you had been previously. During a long run you may well experience 'hitting the wall' when your glycogen levels are seriously depleted. Having well stocked glycogen stores will help you train longer and harder.

How much carbohydrate should I be eating?

If training between five to seven hours per week, you should take approximately 5 to 6 grams of carbohydrate for every kilogram of body weight (or 2.27 to 2.73g for every pound of body weight).

For example: a 70kg runner training six hours per week will need:
70kg x 5 to 60kg x 6 = 350 to 420g of carbohydrate per day.
To calculate your carbohydrate needs per day:
Body weight _____kg (there are 2.2lb to a kg)
Multiply your body weight kg (___kg x 5) to (___kg x 6) = ___ to ___g

What type of carbohydrate is the best?

There are two types of carbohydrate — complex carbohydrates and simple carbohydrates. Complex carbohydrates should make up a large proportion of the diet because they tend to be more nutritious and release energy slowly. They also contain B vitamins, which are important for energy production, iron (essential for making red blood cells to transport oxygen to cells) and fiber; essential for a healthy gut. Simple carbohydrates are generally found in more sugary products and are quickly released into the blood stream. They can be of use when the body needs a quick injection of energy, either before or during exercise.

How soon before I train should I consume carbohydrate?

A carbohydrate rich meal should be consumed around three to four hours before exercising. This tops up your store of carbohydrates. If running for longer than an hour, have a snack around an hour before running. If you are planning to exercise for longer than an hour, take some food or drink containing carbohydrate.

Options to take with you on a long run can include sports drinks, energy gels, energy bars, dried fruit, or bananas. You will need to make sure you've tried these in the run up to your event as many runners can suffer from stomach upsets.

What should I eat after training?

After training make sure you restock your carbohydrate levels. If possible, try and eat within the first couple of hours following your run. Ideally you should take about 60 to 70g of carbohydrate in the first half an hour, then every two hours until you have your next carbohydrate rich meal.

Remember to drink 500ml (16.9oz) of fluid immediately after your run and continue to re-hydrate. Ideally try taking some protein with carbohydrate to aid recovery.

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