What to eat while training for long distance triathlon

The purpose of this post is to give you information about how to fuel your training while preparing for events such as half ironman and ironman distance triathlons. The first thing to take in to consideration is you won’t be doing the same training every day, so why would you eat the same thing every day? You need to think about food as fuel and the how it can effect the quality and effectiveness of your training. No two athletes have the same diet and everybody has different tastes and preferences when it comes to food. This makes it difficult to say exactly what foods someone should eat. Therefore, this post will explain how to think about protein, fat and carbohydrate in relation to training and not say what you should and shouldn’t eat.

Hard/High Intensity Sessions:

Carbohydrate will be the primary fuel source used when training for hard efforts. This means that you need to fuel high intensity sessions with carbohydrate. Our body has a limited/finite amount of carbohydrate stored within in. This is normally around 90minutes worth of exercise but we will never be able to use all of the carbohydrate stored. When glycogen (carbohydrate) levels lower, our perceived level of exertion at a given intensity will go up and our speed/power will lower. This is why carbohydrate intake during races is so important. Please read the article about race nutrition for half ironman and ironman distance triathlons for more information about this. For short sessions (less than 60minutes), you shouldn’t need to take any carbohydrate. You should make your diet have a higher proportion of carbohydrate in the lead up to the session though. The common mistake athletes make when thinking they need more carbohydrate is over eating. All you need to do is shift the balance of what you eat to more carbohydrate and not increase your overall calorie consumption. Sessions that are longer than 75/90minutes and have blocks of high intensity/race specific efforts should be fuelled by carbohydrate during the workout. Again, please read the article about race nutrition for half ironman and ironman distance triathlons for more information about this.

Lower to Moderate Intensity Sessions:

Racing longer distance events like half ironman and ironman require athletes to efficient. The word efficient here is used in relation to the athlete’s ability to metabolise fat while working at a relatively high intensity. As already discussed, we have a finite level of glycogen stored in the body, but we have an almost infinite amount of energy stored as fat. Without going into to too much detail, fat and carbohydrate our metabolised by the body to produce energy. Carbohydrate is the body’s preferred fuel source because it produces energy faster than fat and it yields more energy. However, as stated, this will eventually run out. Fat is harder to metabolise and yields less energy but is stored in abundance. Therefore, an athlete can perform better over longer distance triathlons if they are efficient at metabolising fat for energy. Few people can metabolise fat as the predominant fuel source in exercise where the intensity exceeds 80-90% threshold. Few people, if any, can race a long distance triathlon at more than 90% of their threshold. Most athletes will race a long distance triathlon at 60-80% of their threshold so becoming efficient at metabolising fat as the primary fuel source is paramount. Fortunately, we can train our body to become more efficient at metabolising fat through appropriate training and what we eat. Please read the article about make the easy easy and the hard hard for more information about appropriate training. What we eat before a session will prime our body to metabolise certain energy sources. So, doing easy sessions fasted, such as an early morning run, will typically result in greater fat metabolism. However, think of food as fuel and don’t be afraid of fat. Having a high fat meal before doing an easy session will prime the body to metabolise fat and make us more efficient at using it as a fuel source. This becomes particularly important in longer easier sessions, such as a long easy run done at talking pace. Lot of athletes struggle for energy in longer sessions on the run and bike, even when going easy. This is because most will start to metabolise more carbohydrate towards the later stages of a session. Having a high fat meal will help reduce this and make the body less reliant on carbohydrate. I normally have a four eggs scrambled before doing a long base run or long base bike to prime my body to metabolise fat. It takes time for athletes to get used to get less reliant on carbohydrate and more efficient at burning fat. Some athletes may not be able to go harder than 70% FTP on the bike on a high fat diet initially, but after several weeks of training, they may start to achieve 80% FTP for sustained efforts. This will translate in to greater efficiency over longer distance events as athletes will be able to go harder for longer.


So, think about the intensity of your sessions that you have in a week and plan your diet around them. You do not need to become obsessed about your diet. Just thinking about it in a more logical way can have huge benefits for your training quality and then racing performance. You will know what sessions feel hard and what sessions will feel easier. Most athletes will benefit from having 1-2 high fat diet days per week on easier training days. This is enough to get a benefit and start changing how the body works. Some athletes operate off a completely high fat diet and minimise carbohydrate intake at all times. The evidence suggests that this isn’t as effective as using carbohydrate for higher intensity sessions and racing. Training with carbohydrate is also essential at improving our body’s ability to metabolise it too (Please read the article about race nutrition for half ironman and ironman distance triathlons for more information about this). On a high fat day, an athlete should look to consume at least 60% of their diet from fat. The easy way of working out what you’re eating is by using My Fitness Pal. You can enter all of your diet into this and it will calculate your macronutrients. This means you can find the foods you like to work within these parameters. As with everything, there is some trial and error involved with this and athletes could eat completely different foods within their diet to achieve the same outcome. Once you have grasped these concepts and found the foods that work for you, you shouldn’t have to log it anymore and choices about what to eat will become more automatic but they will based on reason.

Good luck and please get in touch if you have any questions about any of the above information.

Finlay McAndrewComment