Getting your food and drink intake right on race day morning and during the marathon itself, is one of the keys to success. It is important to stress that each individual's needs vary somewhat, but there are some guidelines that should be adhered to.
During your marathon training schedule it is essential that your body adapts to being hydrated. This means drinking plenty of water continuously; not just when you are running but at all times of the day. It is also a great idea to find out which energy drink will be available at the fluid stations on race day and get used to it by using it to fuel your training in the run-up to the big day. We'll deal with the specifics of exactly how much water you'll need as we go.
A simple couple of rounds of wholemeal toast and a cup of tea are a good option, as are bananas and muesli. Try to avoid anything too acidic like citrus fruits and juices, and always make sure that whatever you eat is familiar to your digestive system. Race day is not the time to experiment with exotic alternatives; stick to what you know.
It is perfectly acceptable to keep on snacking on the journey to the event and up until an hour prior to the gun going off. Energy gels, bars and drinks are fine, as are nuts and fruit. It is also important to drink around a litre of water in the two hours before. Don't overdo consumption of food or drink and make sure that you empty your system in plenty of time.
During the Race
Water stations at the big events like London or New York often stretch for nearly 300 metres, so avoid the crush by running to the latter end of the station where it will be far less crowded. Normally the water is distributed in bottles with no caps, but occasionally it could be plastic or cardboard cups. Take a few sips, then throw the bottle or cup well out of the way to the side, ensuring that you don't cause a hazard for another runner along the way. Continue this pattern throughout the entire marathon.
Most big events will have sponsorship from an energy drink, which will also be made available at various stations (though normally not as frequent as the water stations). The energy drinks are generally available every 5 miles or so and can be a well-deserved boost for any runner. It is vital, as stated earlier, that you get used to the exact brand by training with it. If it is Lucozade Sport that will be available, train with Lucozade Sport, not a similar drink or even another variety of Lucozade. It may seem pedantic, but each brand and variation is made up of subtly different ingredients and your body will need time to adapt. The last thing you want on race day is an unsettled stomach.
Other Energy Sources During the Marathon
Many runners also like to carry a small belt bag with a few supplies to keep them going. Energy bars and gels can be a really useful and much needed energy source, especially in the latter stages of the race. You will need to provide these yourself. Gels in particular can have a real impact on your energy levels and prevent you from hitting a wall, but make sure to drink them along with some water. Because they are made up of highly concentrated carbohydrates, undiluted gels can have an adverse affect on your digestive system. It is wise to cap your intake at around four or five during the course of the marathon; any more can prove counterproductive.
If you really think that four or five hours without consuming anything more than water and energy drinks and gels will be impossible, you can by all means carry some extras. There is no harm in a chocolate bar or a few sweets as a mid marathon reward. But, again don't overdo it and end up feeling sick.
Get your intake right before and during a marathon can be the difference between an enjoyable, exciting and ultimately hugely rewarding experience and one that seems like a tortuous nightmare, so take care and plan carefully. Good luck!
If you're interested in entering an event and want to know if you have what it takes, here's an article outlining the minimum requirements for running a marathon and an overview of what the commitment will be: