ironman triathlon diet and nutrition tips

These ironman triathlon diet and nutrition tips might serve as a guide if you are unsure what diet will work best for you.

Through my own experiences I can pass along two very important thoughts you might want to keep in mind regardless of what food choices you choose to get you through race-week, race-eve, and race-day.


It can be a huge mistake to introduce food into your diet just before your race if you have not tried and tested them during your months of training.

All foods are not agreeable to everyone and it’s often a case of trail and error in order to find the perfect combination of food that agrees with your digestive system and provides the necessary fuel to propel you to the finish line.

If certain foods do not sit well with you and often cause sluggishness and upset stomach when eaten just before a long training swim, there is a good chance they won’t work for you on race-day when the start gun goes off to begin the 2.4 mile swim. Hopefully, these ironman triathlon diet and nutrition tips will help steer you in the right direction.

If the food you take with you on a 80k-100k bike training ride does not provide you with the necessary energy near the end of your ride, they will most likely not work any better out on the 180k Ironman bike course.


There is no doubt that one of the wisest choices you can make long before race day is to book yourself a kitchenette at the race venue. Your first task when you arrive should be to go the the grocery store and stock up on all the food you are familiar with.

If you are within driving distance of the venue that’s even better. You can bring some of your favorite food from home.

Perfect choice for a triathlete

The closer you can stay to the diet that suited you best at home during all your hard training the better off you will be. It’s a crap-shoot to eat at restaurants the week before the biggest race of your life.

There is far too much at stake to take any chances on this front. Weeks, months, or perhaps years of training, sacrifice, and the expense of simply getting too the start line of an Ironman is too much to risk because of poor food choices in the days prior to the race.


Everything you eat during the week before your Ironman should be considered part of your race strategy and preparation.

If your race is on a Sunday as most Ironman races usually are than Sunday, Monday, and Tuesday before the race would be good days to begin to slightly increase your protein and fat intake. It would also be wise to gradually increase your sodium intake especially if you tend to sweat a lot.

Wednesday, Thursday, and Friday are the ideal days to gradually begin the carbohydrate loading process. Converting carbohydrates into glycogen is done over time and as a result this is best accomplished by having several small complex-carbohydrate meals during the day as opposed to huge meals every evening.

plate of pasta

Eat your favorite pasta meals before the race.

If you have favorite complex-carbohydrate pasta or brown rice meals it is during these three days when you should make them the cornerstone of your pre-race diet.

I remember when I first began distance running some 35 years ago there was this belief that a huge pasta meal the night before the big race was the ticket to success. It is far easier on the digestive system to build up your glycogen stores over several days. There is only a limited amount of glycogen the average person can possibly store, so eating more carbohydrates once your glycogen stores are maxed is overkill and has no added value.

A good balance for these three days of carbohydrate intake would be 60% carbohydrate, 15%-20% fat, and 20%-25% protein. This may be a bit higher intake of protein than you would normally eat, but demands on your body on race-day will cause proteins to break down and increasing your protein intake may enhance your over-all performance.


Personally I always ate my last meal on race-eve between 3-5 p.m. and never later. I just felt more comfortable having the extra time to digest that meal. As my glycogen stores were already topped up this was not an over-sized, huge meal.

brown rice casserole

Brown rice is a great choice as a complex carbohydrate

Perhaps this statement courtesy of Dave Scott, 6-time Ironman champion says it best and reinforces why I feel it is a wise decision to eat your last meal early on race-eve. Who better to get some ironman triathlon diet and nutrition tips from?

Shift your last meal (dinner) to finish at an earlier hour, preferably between 5:00 and 6:30 p.m. This will allow your body to digest and your bowels to eliminate foodstuff in preparation for an early morning race. Eat a small snack of 100 to 200 calories before bed time (8 to 9 p.m.) if desired.

Personally I ate even earlier than Dave suggested as for me 6:30 p.m. was just too late and I also chose not to have a night-time snack.

This is something you should experiment with when you have long training days scheduled. Try eating early one night at an earlier time(say between 4:00-5:00 p.m.) and then perhaps later the next time (5:50-6:30 p.m.) the night before one of your long training sessions and see how your digest system reacts the next day to the early and late meals.

If you find that you are 50k into a 100k bike ride and nature calls, perhaps you ate to late the night before and an earlier dinner the night before would be a better choice.


As your glycogen stores should be topped up at this point, eating a large breakfast the morning of the race is not needed nor is it a good idea just before a 2.4 mile swim.

Personally I preferred being awake between 3:30 and 4 a.m. for a 7 a.m. race start. Breakfast consisted of one banana and two slices of whole wheat toast and a cup of tea.

Again it is a matter of preference, but it would be wise to keep solid food to a minimum with the race only hours away.

Conventional wisdom seems to be that ideally 500-800 calories would be about right on race morning. I always went on the lower side of the scale to prevent any digestive issues during the swim.

toasted whole wheat bread

Whole wheat toast is a good choice race morning.

Here is what six-time Ironman Hawaii winner Mark Allen has to say about breakfast before an Ironman.

Pre-race breakfasts can be one of the biggest questions for people. The answer of what to eat lies in what you would normally consume before heading out for a very long day of training. If you would eat more than a couple of bananas, then on race morning you will also need more than a few bananas. Do what you would normally do. The thing that can be different than on a training day is that you might prefer to get your calories from liquids rather than solids. There are many meal replacement drinks that work perfect for this.

They enable you to drink 500-700 calories on race morning very easily. Eating the equivalent amount of calories from bagels and bananas can be extremely difficult and impractical.


When you exit the water after a long and perhaps physically and emotionally demanding swim that required you to be in the horizontal position for 2.4 miles it will take your body a bit of time to adjust to being vertical once again.

It just adds to the stress if you begin piling on the food and drink the moment you set foot on solid ground.

It would make more sense to wait for 15-20 minutes until you are settled into a smooth rhythm on your bike.

At that point begin sipping on a replacement drink and over the first hour take in about 200-300 calories. As you go beyond that first hour your calorie intake should be increased to 300-500 calories per hour using your complex carbohydrates of choice.

whole wheat bagel with peanut butter

Whole wheat bagels with peanut butter were perfect for the first half of the bike leg.

For some reason it always seemed like this was the ideal time to take on carbohydrates in a solid form as opposed to gels for instance that might make more sense in the second half of the 112-mile bike.

My personal favorite the year I recorded my fastest ever Ironman time was whole wheat bagels with peanut butter. I cut them into halves and put them in individual bags that tucked easily into my cycling jersey.

A large whole wheat bagel with 2 tablespoons of peanut butter contains 550 calories. The peanut butter contains 140 grams of fat which will may also help you through-out the bike.

Three whole wheat bagels with peanut butter over the first 3 hours of the bike will provide 1650 calories which is about perfect. You might have a particular whole wheat sandwich or other complex carbohydrates you prefer.

It’s easy to figure it out. Just try different combinations on long training rides months before your race.

The time to include carbohydrates(like gels for instance)into your nutrition plan would be during the second half of the bike as they are easily and quickly assimilated by the body.

Eating heavier carbohydrates in the late kilometers of the bike is not a great idea as your body will not have time to assimilate them and this may cause you problems out on the run course.

I really believe that if you have a sound nutrition plan on the bike course you will not need to eat very much(if any)solid food at all during the marathon.

Although it may be tempting to try the chocolate chip cookies, grapes, protein bars, bananas, and any other solid food you might have access to at the marathon aid stations, it might be wiser to stick with water and your favorite replacement drink for the duration of the marathon.

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3 thoughts on “ironman triathlon diet and nutrition tips

  1. Thanks , Ray. I made heavy weather of IM South Africa ’09 due to poor nutrition planning. I’m heading back on Sunday to settle the score! Still, it looks like I need to boost my solids beyond what I’d planned, especially for the first half of the bike.

    Any ideas on suitability of chocolate milk drinks on the morning of the race (or even at T1)?

    • Hi Arni

      For the last few years chocolate milk has been promoted as a training and racing “recovery drink” that will help you perhaps perform better next time time out. Low fat chocolate milk does appear to have a great balance of proteins, carbohydrates and nutrients but I would question using it in a race because of the possibility of stomach issues. It would make more sense to be using all through your training for recovery and better performance next time you train, and perhaps in the last few days leading up to the Ironman. regardless it would certainly be something I would try in training first.

      As to eating on the bike, taking in complex carbohydrates in the first half of the bike makes perfect sense. It will help your body replenish glycogen stores for late in the bike and for the marathon. Early in the bike also seems like a time when the body will accept solid food more readily. Early in the bike the goal is to have complex carbohydrates that are assimilated into your system over time, as opposed to a gel for instance that is assimilated quickly for shorter bursts of energy. Gels would make sense later in the race. I would avoid eating anything solid in the last third of the bike because you may cause yourself problems in the marathon as there is simply not enough time for your body to assimilate solids at that point.

      In a six or seven hour bike leg, hour two, hour three, and perhaps half of hour four on the bike are the optimum time to take in solid complex carbohydrates. The first hour out of the water you just want to ease into eating and drinking as your system re-adjusts from being horizontal to vertical and your respiration and heart-race even out.

      Best of luck in Ironman South Africa! Also, it might help you greatly to read my post on the Ironman Triathlon-Negative split strategy. If you buy into the concept, your Ironman result this time around may be far different.

      Ironstruck Ray

  2. Thanks again, Ray! I’m busy writing out my nutrition schedule for the race right now, and am incorporating your recommendations. I’ve read the negative split piece, and will definitely be holding back on the bike…though that was the plan last time too, and I lost my head when people started flying past me. Older, wiser and more disciplined this time, I hope.

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