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Food and Fluid for Your Marathon

Category: Sports and exercise nutrition
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 (





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 carbohydrates 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:

  • Bread / baps / rolls
  • Breakfast cereal
  • Potatoes / pasta / rice / noodles
  • Scones / crackers / fruit cake / cereal bars
  • All fruit
  • Carrots / parsnips / peas / sweet corn



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:

  • Lean red meat / fish / chicken / tofu
  • Milk and dairy products e.g. cheese / yoghurts
  • Legumes e.g. beans / peas / lentils
  • Nuts, nut butter and seeds 




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.



  • Aim to drink regularly throughout the day and begin each training session well-hydrated.
  • Keep an eye on the volume and colour of your urine as a measure of hydration status.
  • If you are passing less urine or the colour becomes darker than normal, then you may not be drinking enough fluids.



  • For runs longer than 1 hour aim to drink 100-150 ml every 15-20mins or at a rate that is comfortable.
  • An isotonic sports drink may help to replace fluids and provide a source of carbohydrates during longer runs.



  • To assess fluid losses post-exercise, it can be helpful to weigh yourself before and after your run.
  • Remember to take into account any drinks you have consumed. Aim to replace 150% of any weight lost within 4-6 hours e.g. 1kg weight loss = 1.5L fluid.


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




  • Increase the number of eating occasions (6-8 times/day). Base all meals and snacks on foods that are high in carbohydrates (see list above).
  • Eat 5 portions of fruit and vegetables daily to ensure adequate intake of vitamins and minerals
  • Reduce your intake of high fat foods e.g. chocolate, cakes, biscuits, fried foods etc.
  • Training is a good time to experiment with the type and timing of food you consume before running in order to avoid any digestive discomfort like stomach cramps, diarrhoea or wind.
  • It is important to trial different carbohydrate replacement strategies (sports drinks, gels or bars etc.) during training runs to make sure they do not upset your tummy or give you diarrhoea.
  • Training is a good opportunity to practice fluid replacement in terms of timing, amount and type of fluids e.g. water, isotonic drinks or diluted fruit juices.
  • Remember to choose a snack containing both carbohydrate and protein within 20-30 min of stopping training (see post exercise snack list).
  • Ensure adequate rest between your training sessions.




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

  • Ensure your last meal the day before the marathon is high in carbohydrate with a  lean protein source. Eat what worked for you during training and avoid trying new foods at this late stage.
  • Drink enough fluids the day before and morning of the marathon to ensure you are hydrated
  • A high carbohydrate (low fibre) breakfast should be eaten 2-4 hr before a marathon e.g.
    • Breakfast cereal (e.g. porridge / muesli / shredded wheat) + low fat milk and / or toast + low fat spread + jam / honey 
    • Fruit / fruit juice 
    • Low fat yogurt
  • Extra snacks can be taken approximately 1hr before the race to boost your carbohydrate stores e.g. cereal bars / fruit / yogurts / isotonic drinks.
  • Drink 300 – 500 ml water / isotonic drink before the race to ensure you are fully hydrated.


During the Race

  • Drink fluids regularly throughout the race e.g. 100 – 150 ml every 15 min during the race. Water is usually available however isotonic drinks are the most suitable way of getting both fluids and carbohydrate at the same time.
  • Take 30 – 60 g of carbohydrate every hour e.g.
    • 600 – 1000 ml isotonic drink
    • 1.5 - 2 carbohydrate gels
    • 45 – 85g dried fruit


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:

1. REFUEL energy stores with carbohydrate!

2. REPAIR muscle tissue with protein!

3. REHYDRATE body fluids with fluid and electrolytes!

  • Eat a recovery snack high in carbohydrate, with a source of protein within 30 min after finishing the race. Choose easy to digest foods that are low in fibre and fat e.g.
  • 500 ml flavoured milk + cereal bar / fruit
  • 300 – 400 ml milkshake / fruit smoothie
  • 2 pieces of fruit and 200g fruit - flavoured yoghurt
  • Have a follow up meal containing carbohydrates and some protein within 2-4 hrs of finishing the race e.g.
    • 60 g breakfast cereal and low fat milk
    • Half a tin of baked beans and 2 slices of toast
    • Sandwich / roll / wrap + chicken / ham / egg / tuna and salad
    • Jacket potato + tuna / baked beans / low fat cheese
    • Spaghetti bolognaise
  • Make sure to have high carbohydrate meals and snacks for the next 24 hrs after the run
  • Replace fluids and electrolytes by drinking fluid slowly over the next 24 hrs. Don’t wait until you feel thirsty to have a drink.
  • Ensure you have rehydrated before consuming alcohol after the race



Created by  Lauren Delany MSc 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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