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Food and Fluid for Your Marathon

Posted in Sports and exercise nutrition

Running a marathon distance of 42.2km requires extensive training and preparation to enable your body to be physically and mentally ready for the challenge. Whether you are a first timer or a veteran distance runner, the importance of optimal nutrition is the same. The right diet can support the body through high training loads and help to prepare for and see you through the big event.

With your marathon on the horizon, the next few months of diligent training will challenge your body both physically and mentally. It is vital to support your training with good nutritional practices and this factsheet will help to answer your questions in the lead up to the big day. Remember for more detailed expert advice you can contact a sports dietitian through the Irish Nutrition and Dietetic Institute (link).



Distance runners require high energy intakes to allow the body to undertake long, intense training sessions. Carbohydrate is the most critical fuel source for marathon training and is stored in the liver and muscles as glycogen. These fuel stores are limited and need regular replenishment. A diet high in carbohydrate is essential to keep these levels topped up.

The recommendation for carbohydrate intake for runners is between 5-10g carbohydrate/kg body weight/day. As training load increases and you start running longer distances, the amount of carbohydrate you eat also needs to increase. In order to meet these high carbohydrate demands, it is important to base all meals and snacks on foods that are high in carbohydrates.

Good sources of carbohydrate include:


Moderate amounts of protein are important to support and repair your muscles, in particular during intense training periods and to optimise recovery (see ‘after the finishing line’ section below). The recommendation for protein intake in distance runners is 1.2-1.4 g protein/kg body weight/day. Protein intake is usually proportional to total calorie intake, so the more food you eat the more likely you will meet these needs.

Aim to include a good source of protein at lunch and dinner; consume milk regularly throughout the day and include sources of protein in some snacks.

Good sources of protein include:


During training you lose fluid through sweating. Unless these fluid losses are replaced by drinking, you run the risk of becoming dehydrated, which can cause fatigue and impair your performance. Fluid requirements are different for everyone and it is important to develop your own hydration strategy in training and for races. If the weather is warm and/or humid you will need to drink more than usual to replace the extra fluid you have lost through sweating.




You can make your own isotonic drink using the following recipes:

Option 1: Option 2:

50 – 80 g sucrose

1L warm water

Pinch of salt

Sugar-free squash for flavour

500 ml water

500 ml unsweetened fruit juice

Pinch of salt



Time Sample Menu

60g wholegrain cereal (e.g. porridge / bran flakes / muesli) + low fat milk

Fruit e.g. banana / apple / dried apricots / raisins

200 ml fruit juice

Training run

Isotonic drink

Post training

500ml flavoured milk


Cereal bar


Wholemeal roll / bap / bread + low fat spread

+ Chicken / ham / tinned fish / egg / low fat cheese

+ salad

Fruit / fruit juice

Slice of fruit cake / cereal bar

Afternoon snack

Yogurt / fruit / handful of nuts and dried fruit


Meat / fish / eggs / beans

Potato / pasta / rice (50% of plate)

Side salad + low fat dressing

200ml low fat milk

Fruit salad

Evening snack

60g wholegrain cereal + low fat milk


Before the marathon

During the race

NOTE: Experiment with what works for you during training. Try and avoid last minute changes to your fluid and carbohydrate strategy by race day free promotional products.


After the finishing line

The 3 rules of recovery are:

REFUEL energy stores with carbohydrate!

REPAIR muscle tissue with protein!

REHYDRATE body fluids with fluid and electrolytes!


Created by  Lauren DelanyMSc Sport and Exercise Nutrition, BSc (Hons) & PG Dip Human Nutrition and Dietetics, ISAK1 October 2013, updated by the SNIG April 2016.

Review date: April 2019

© 2016 Irish Nutrition and Dietetics Institute, INDI. All rights reserved. May be reproduced in its entirety provided the source is acknowledged. This information is not meant to replace advice from your medical doctor or individual counselling with dietitian.  It is intended for educational and informational purposes only.

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