Since I moved up to the Ironman distance, I have realised how important nutrition is for both training and racing. With the increased training volume and increased race duration, energy demands are significantly higher than shorter distance racing. Most of my learning has been based on many years of trial and error, but being fairly new to the Iron-distance I am sure I still have a lot to learn.
Training for an Iron-distance race at any level requires long training sessions, and proper fueling around these sessions can make a world of difference. Calculating your energy demands is the first step; this is normally done for you through your cycle computer or running watch, however many free apps can give you an estimated calorie expenditure. Knowing your expenditure allows you to ensure you do not create a large energy deficit, which would inhibit recovery. Aim to consume the majority of those calories expended throughout and post-session. Not only will this help recovery for the session, it will also help you maintain your energy levels throughout a training block.
Race nutrition becomes even more important during the longer distance races. It is almost impossible to replace what you burn as the gut cannot process energy quick enough. Hence your race intake is limited by your gut's processing rate. A general rule that many follow is to aim for 90g of carbohydrate per hour, however the actual ideal amount will differ for everyone. For a more detailed look at optimal race nutrition, take a look at the article, 'Prepping for your Big Race,' by The Link's nutrition and health writer, Tim Davis. For the optimal rate of energy consumption for you, it's a good idea to visit a doctor or nutritionist to determine what your individual needs are, and then you're best to learn through trial and error (unless you have access to a lab to test). If you have too many carbohydrates per hour than your gut can process then you will feel quite sick and bloated - this indicates you need to reduce your consumption for your next trial. However, if you have no gut problems in your initial trial, you could try to increase the consumption rate.
This is a short summary of my approach to basic everyday and race nutrition that may be a useful starting point for beginners. I would recommend to get your own individual plan personalised to your needs by a qualified nutritionist.
By Mike Phillips - Pushys Sponsored Athlete