Ironman Nutrition Strategy – What to eat during an Ironman Triathlon

Sports NutritionOne of the most important aspects of an Ironman Is Nutrition. What to eat during the race. Weather you are out there for 7hours or 17hours you will need to top up your bodies fuel reserves. For most people eating isn’t normally a big ask. But while cycling and running hard for long periods the body doesn’t really want to take on the fuel it needs. So people naturally neglect their fuelling. Developing an effective Ironman Nutrition Strategy and executing it on the day will see you get round in your best possible performance and stave off the dreaded “bonk”. So This post will examine what to eat during an Ironman Triathlon, and how to develop your own nutrition strategy and why its essential you test it before race day.


The body is able to hold a finite amount of glucose in the Blood and Muscles ITs around 2000 Kcals. As you exercise this is slowly (or Quickly) depleted. When it runs out your performance is pretty much over. It can be a challenge to even walk as you near that level and as you fully run out you will be lucky to keep upright. This is known as Bonking or Hitting the Wall. With a Full tank (200 Kcals)

The human body is good for around 1.5 – 2 hours of hard exercise or a few hours more at more moderate efforts like ironman. This is clearly WELL short of the times required to finish an Ironman so everyone is going to need to eat to replenish the fuel.

The body takes its energy from a few different sources not just the blood sugar so easier efforts utilise more fat as fuel than harder efforts hence why slightly less intense efforts allow longer before you must eat.

Carb Loadingcarbohydrate

Your fueling strategy starts the day before the race. By eating a large amount of calories derived mainly from carbohydrate you ensure you have a full tank. People often take this a little too far though. You only really need eat your usual amount of calories only made up from mainly carbohydrate. There is only so much your body can take on. Any more is converted to and stored as fat. So just aim to eat mainly carbohydrate based foods but don’t over eat or binge. But its perfectly ok to eat quite freely and enjoy your pre race food. Too much over indulgence can lead to “carb-Unloading” a slang term relating to the need to visit the bathroom too often!

Its a very good idea to drink plenty too. Ensure you are well hydrated.

ENJOY: Bread, Pasta, Potatoes Porridge oats, Granola, Flapjack, Rice, Pizza (Low Cheese), Cake, Really anything high in carbs and preferable something YOU enjoy. You have been good for months begin to let your hair down.

AVOID:  FATTY FOODS. Really try hard to avoid fatty foods today. They help “loosen” things downstairs, which can be undesirable. So Cheese, fatty fish, Chocolate, Nuts, Oils, All things that are part of a normal healthy diet are best avoided the day before. In moderation they are fine but avoid too much. Again I try to avoid things that have a higher risk of food poisoning, shell fish for example. Caution is prudent this close. Avoid eating late also, you need time to digest.


The most important meal of the day! Overnight your carb stores have waned, and this is your final chance to get back to FULL. Its probably the last time you will eat properly for a while. Simple sugars are the order of the day. White bread (toast) with honey or jam. Porridge, Granola, Banana, even Pancakes. You might find this a struggle as its normally at a very early hour and nerves are ratcheting up. I also drink a Caffeinated drink. normally Coffee. This helps get things going so you can visit the loo to “loose some weight” before the race. You don’t want your body waking up half way through the swim.

After that just sip sports drink to keep fluid and sugar levels up as you approach the start.

I also use redbull at this stage but ONLY if you have tested it and can tolerate it.

 What to Eat

less than great nutrition

Swim: Nothing, its only an hour and a bit. Just focus on the swim. Its often nice to have a flavoured drink just after the swim (transition Bag) to wash your mouth out.

Bike: The first thing to decide is whether you want REAL food or energy supplements.  Neither is right or wrong and its entirely personal. Most faster athletes tend to edge toward Energy supplements. While Real food tends to used more prevalently near the rear of the field. But that is mainly due to the fact energy foods are “easier” to consume and the faster guys just don’t waste time trying to force down a ham sandwich.

You first need to find out what will be available on the course. Its imperitive you try anything they are handing out before you try it on race day. some energy products just don’t sit well with some people. The last thing you want is to find out on race day you can’t stomach the energy drink they provided that you were going to rely on!

If you are going for real foods you’ll have to find a way to carry them. A Cross bar mounted Energy pack is a great way to take some food but its not going to be enough if you are solely relying on your own food. Most people pre-load pockets of a cycling jersey to carry extra food and also use the special needs station to store a top up in food supplies.

Anything Mainly consisting of carbs is fine to eat. Sandwiches, Wraps, Soreen/malt loaf, Flapjack, Jelly Babies, Bananas are all favourites of mine in the real food world. Basically anything “easy” for you to eat. Both in terms of physically, and mentally. Later in the ride you probably won’t want to eat. so its got to be appetising. Also ensure a selection, you will get bored of one food very quickly.

As for Energy supplements if you can Manage the Course products that’s great. It makes like ALOT easier. Just carry a supply of alternatives in your Cross bar Bag. Simply take whatever is on offer at each aid station. Banana, gel, energy bar. Along with the energy drink.

Example: I personally always pick up one bottle of energy drink to replace my current (empty) bottle. I also pick up a bottle of water but carry it with me While I eat the Banana/Gel/Bar I have picked up. I then have a large drink of water to wash that down. I then ditch the bottle, in the appropriate place and carry on never stopping. I then slowly drink the energy drink before I get to the next Aid station. I also try and eat something from my own stash in between as well. Or take something extra from the station with me as well.

Its important to study the aid stations before hand as well as some can appear further apart than they seem. One aid station at the top of a hill can take an awful long time to get to.

Which ever route you choose Its important to remember you can only take on so many calories. Any more and you risk stomach upset and your body won’t process it anyway. A little and often is the key. The advised amount is 60-9grams Carbohydrate an hour.


High 5 Energy Gel : 90 Kcals 23 g Carbohydrate

High 5 Energy Source 750ml : 174 Kcals 44 g Carbohydrate

Power bar : 199 Kcals 39 g Carbohydrate

Cliff Bar : 254 Kcals 37 g Carbohydrate

Homemade Flapjack 90g: 340 Kcals 45 g Carbohydrate

drops of water

Hydration is hugely important. You must be continuously drinking. You will lose a lot of water and salts through sweat and this must be replaced. Drinking water is not a great idea as you don’t replace the salts. I always drink either an energy drink containing electrolytes (all course supplied drink will have this) or a Zero calorie electrolyte drink such as Nunn or High5 Zero.

Run: By the time you hit the run your body isn’t really going to be keen on taking on much food. And that’s Ok really. During the run as long as you have eaten well on the bike you can get away with only minimal fuelling. The efforts are really quite low by this stage and you will be metabolising a lot of fat. But its still important to eat. And even more important to drink.

I find a Bit of something from every feed station, while taking a walking break is more than enough. Often events have a bit more variety on the run feed stations. I’ve have Crisps, Cake, Biscuits, Jaffa Cakes, Salty Crackers, Even SOUP. At run feed stations. Just take what you fancy along with some drink, walk as you eat it then carry on your day. Its really that simple.

I don’t really advise taking your own food with you, it will get warm and battered. But if the organisers really are not providing anything you like there really is no choice.

Its worth noting that the salty foods provided are often VERY appetising, I always take these, that’s because your body is craving salt to replace your losses. Listen to it!

Note on Special Needs Stations:

Most Events offer what is called a Special Need station. This is simply somewhere you can pick up a bag you have pre packed with anything you think you may need. This is a god send if you are taking all your own food. You simply hand it in before the race and they take it to a designated spot on the course for you to pick up. Depending on the race there will be a bike only or a bike and run special needs Station.

Practicing Your Strategy

It is ABSOLUTELY essential you test your strategy. I just can’t stress that enough. People regularly fail to finish or have terrible days because they couldn’t handle the brand of energy drink on offer. I myself have fallen foul of this pitfall. Whatever you plan on doing on race day make sure you have tried this out in training. Your big rides are perfect. If you plan on using the Course Aid stations find out before what the stations will offer and get hold of some to try during your long training sessions. Make sure whatever you have is Easy to consume and that it sits well in your stomach. Ensure that’s still the case after 5 hours on the bike.

Always remember the Golden rule of Ironman. NOTHING NEW ON RACEDAY!

Test everything and always have a few options. Because sometimes you just won’t want one thing. So it always pays to have a back up fuel to go to if your stomach is rebelling.


Ironman racing is hard. And it puts a large amount of stress in the body. Sometime it can go into shutdown and an refuse to take on any food. Or even be quite happy to return the food you have eaten all over your shoes. Dealing with these issues can be the difference between a good finish and a DNF or trip to the medical tent.

Bike: If you start feeling unwell and unable to eat on the bike its a big worry. My only DNF came from a fuelling breakdown on the bike. About 30 miles in things went wrong and I was unable to recover. The day was hot and I was sufferings from an allergic reaction to mosquito bites. My digestive system shut down and I was unable to eat or drink for over half the bike leg. This meant any chance of running the marathon was off the cards. Its hard to suggest a remedy to such a situation. Less severe stomach issues can be managed. Its normally best to try and take a little bit of food on often. Rather than trying to force a large amount down. If you are struggling to take on the energy drink provided try and water it down more. its hard on the go so you may need to stop and mix some bottles with extra water. Drinking Plain water can be dangerous as you may be loosing so much salt from sweating. Try  to so everything you can to keep eating. Also Remember with time your appetite may come back, so try taking a few miles easier to see is you digestive system recovers.

Run: This is where most people start to feel a bit queasy. The up and down jiggling motion can lead to problems. As there are lots of aid stations on Ironman Runs just try snaking on very small amounts of food with water/energy drink. You may find the flat coke sits quite well too. But make sure its fully flat, fizzy drink are unlike to help here. Also look at the salty snacks as these can be more appetising than another sickly gel.

Post Race

After the race its main a case of eat whatever you can stomach. A feast of post race food is normally laid on for the athletes but all too often No one really fancies anything. But you should try and eat something, but what really doesn’t matter just eat what you can through the evening and drink plenty. Feel free to have a little tipple, but don’t expect you’ll be glugging the champagne. Very soon only one thing will be on your mind. Bed.

Day After

Seriously? You have just done an Ironman Eat what the hell you want. Just make it a treat! whatever the means to YOU.


Hopefully This article is of use to any aspiring Ironman athletes, Its often hard to know exactly what and when to eat while racing. We know there are feed stations but we don’t always know the best way to use them. Hopefully I have clarified most of this but feel free to let me know if you have any questions. The Nutrition side of Ironman racing is a complex business. Also let me know what foods you eat during training and racing?

Stephen James


  1. Great point about loading but not OVERloading on carbs the day before. Also, craving salty things because your body needs to replenish what it’s lost. It seems counterintuitive when you really want to hydrate but makes total sense! Thanks!

    • Hi Toni.

      Yep its a over loading the day before is a common mistake as everyone seems to know the importance of Carb Loading but seem to take it too far.

      The Salt replacement is as you say is counterintuitive. But tis very important as we sweat we lose salt and water. As the natural instinct is to drink water to replace the sweat it starts to lead to an imbalance. This stops our body functioning correctly. This can lead to impaired performance or muscle cramps in the less severe and even full break down or even Death in the extreme.

      Unfortunately there have been a few deaths in long distance sports attributed to drinking too much water without salt/electrolyte replacement.

      Simply replacing your electrolytes with energy drink or salty foods is all that is required.



  2. Being and old jock I really enjoyed your posts ,especially your personal story. Your use of self depreciating humor is very effective and leaves the reader wanting more. No one can say you did not do your homework. I too have run 6-10k’s and know well the work and rewards involved. Great work.

    • Hi Larry,

      Thanks for the comment. Glad you enjoyed reading the post.

      Yep I’ve done plenty of homework. I’ve done the hard miles and made the mistakes so hopefully my readers don’t have to.

      Thanks for reading


  3. Hi Steve, great post, very comprehensive! I was just wondering if you had any particular brand of energy drinks or gels that worked for you in particular? Thanks Sean

    • Hi,
      Thanks for reading Sean. I avoided recommending particular products in this post as really I wanted to get across the point its very personal and what works well for myself would not necessarily work for you or anyone else. However I personally use HIGH 5 Products mainly. They are on the cheaper end but quite effective. I use the “high5 energy gels” and the “High 5 Energy Source” energy drink powder. Also I do like the “high 5 ISOgel” for running as they do not require you take water with them.
      Its very important to experiment yourself though and find a best fit for you.

      Thanks Steve

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