Your Ultimate Ironman Nutrition Guide

Apr 02, 2024

What are the key nutrition considerations for a full-distance triathlon?

There is no doubt that adequate training preparation is required to be successful at completing an Ironman. However, having the right amount and type of fuel is equally essential for this preparation and for the race day to be successful. I’ve seen how poor nutrition decisions have ruined races for many athletes wasting all the time, energy and money they invested as part of this preparation, and I don’t want that to be your case. This is why I have decided to put this Ironman Nutrition Guide together with the key nutrition considerations for your full distance triathlon to be successful.

Nutrition for Ironman Training

Before we jump ahead and talk about what you’ll need on race day, it is essential to talk about how you will fuel the preparation and why this is important.

The purpose of training is to trigger physiological adaptations in your body that eventually will translate into better performance. Many people don’t understand that nutrition during training goes beyond eating enough calories. The nutrients in those calories are also critical for those physiological adaptations to occur. Therefore the purpose of food during this stage is for your training to be as efficient as possible.

These are the key considerations so nutrition can support your training.

Eating enough

Now is not the time to go on a new diet or try to lose weight. Restricting your energy intake while your training volume increases will only result in catastrophe. Poor performance, higher risk of illness or injury and lack of energy are only a few of the consequences of not getting sufficient calories.

Getting all essential nutrients

Carbohydrates, protein, fat, vitamins, and minerals are all essential for your body to fulfil its core functions, and they all have a role to play in performance enhancement. This is why beyond looking at calories, it is vital to ensure that your diet is well balanced and varied, so all essential nutrients are present.

Eating at the right time

There are critical moments in your day when nutrition becomes even more important. That is before, during and after training.

Before training

You want to ensure that your body has sufficient energy to commence the activity so your body doesn’t need to go under unnecessary stress as part of completing that training session. Carbohydrates are your friends and you will need them at this stage.

During training

Some level of nutrition will likely be required for activities with a duration longer than 90 minutes. The longer the duration and the higher the intensity, the more you will need. This is also the perfect time to try the foods and products you intend to use during your race to get familiar with them and decide which ones work better for you.

After training

The nutrients you consume after your training go straight to where your body needs them the most to stimulate the post-training recovery and start working on those adaptations. Both carbohydrates and protein are necessary during this stage. It is also important that you remember to rehydrate, especially if you’ve been training in the heat.

Nutrition for Ironman Racing

Now that the training is covered, it’s time to guide your Ironman nutrition on the day of the event. The goal is to keep your body energised without disturbing your gut. Easier said than done. Here’s what you need to consider.

Fuelling up your tank

Before heading on to race day, you must ensure that your fuel reserves are full. The best way to achieve this is by following a carbohydrate-loading protocol. I know that pasta parties are pretty popular to increase carbohydrate intake before a race. However, eating pasta the night before your race will not be sufficient to fuel up your tank.

For the carb-loading to be effective, you will need to increase your carbohydrate intake at least two days before your race and preferably three. The guidelines suggest an intake of 7-10g of carbohydrate per kg of body weight. This means that if you are a 70kg athlete, you will need to consume between 490 and 700 grams of carbohydrate per day. In case you were wondering, the equivalent is at least 30 slices of bread or 8 cups of rice.

Now, before you go and stuff your mouth with rice or bread (please don’t), here are some ways to help you increase your carbohydrate intake without drastically increasing the volume of food you consume.

  1. Split your meals into three main meals and three snacks. In each of these, ensure you have high carbohydrate foods (fruits, rice, pasta, bread, wraps, oats, etc.).
  2. Adding energy-dense options such as sugar, jam, or honey to your meals helps increase your carb intake.
  3. Drinks are pretty helpful as well. These days, you can have a glass of juice or sugar-sweetened tea and some Gatorade/Powerade throughout the day.
  4. Try having 1 to 2 extra servings of carbohydrates per meal (i.e. if you usually eat half a cup of rice, try having a full cup).
  5. Reduce your fat and fibre intake to avoid any stomach upset.

Infographic with carbohydrate loading

Race day morning meal

This is the moment when you finish topping up your fuel reserves. Overnight your body uses glucose from your liver as energy while you’re sleeping, so the purpose of that meal is to replenish those energy losses. Ideally, you want to have a meal with 1 to 4 grams of carbohydrate per kilogram of body weight one to four hours before your race starts. As a rule of thumb, I like matching them. One gram if eating 1 hour before, two if 2, etc.

Here are some options to guide your nutrition choices on the morning of your Ironman. Always make sure you’ve tried this meal before during training.

Race day nutrition

Alright, now that we know what you eat months and days before the event matters, it’s time to talk about what you will eat and drink on race day. During the race, we want your body to stay energised for as long as possible and keep your gut from suffering.

Staying energised

While moving, your body is using both carbohydrates and fats. Carbohydrates are your primary energy source, and your body is very efficient at using them. However, you can run out of them very quickly. Therefore, even after following a carb-loading, you still need to eat carbs during your race.

The guidelines suggest that for ultra-distance races such as the Ironman, the carbohydrate intake must be between 60-90 grams per hour. This can come from various sources such as sports drinks, energy gels, energy bars, chews or homemade food. For many people, relying on a single energy source (e.g. getting all carbohydrate from gels or drink) doesn’t go well, but some athletes prefer this method. I recommend choosing a baseline sports drink, gels and a solid option and rotating through them with most energy coming from the drink and gels.

To decide which mix works best, you need to try these combinations and quantities ahead of the race. The long training sessions are ideal for doing this. This takes me to the next point.

Staying hydrated

Dehydration can seriously affect performance and your body’s ability to handle the heat. However, overhydration is equally important and severe, with some athletes developing exercise-associated hyponatraemia due to poor hydration. This is why being aware of your sweat rate ahead of race day will help you plan an adequate hydration strategy that allows you to consume sufficient fluids to keep your dehydration levels within healthy ranges.

Avoiding gut upset

Gut issues during ultra-endurance events are relatively common. Having the proper nutrition strategy and gut adaptation is critical for minimising the risk of this being your case.

Not all foods are created equal, and for those athletes above the 60g per hour intake, looking at the carbohydrate ratio of the food they are consuming is essential to ensure the gut can handle the absorption.

Hydration also plays a significant role in supporting food absorption. It is not uncommon that the prevalence of gut issues increases in races with high temperatures and high levels of humidity. This is due to dehydration's impact on the gut’s ability to absorb food.

Gut adaptation needs to occur during the training stage. To be successful, you will need to practice your nutrition using the type, quantity and frequency you intend to do on race day.

The final remarks

An Ironman is a big commitment. Therefore, working on your nutrition alongside your training preparation and planning a strategy well ahead of the event is indispensable to achieving a successful race.