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Eating for IRONMAN

Eating for IRONMAN


The amount of training, time, energy and commitment it takes to get to the start line of a half or full IRONMAN is enormous. You may face months of sacrifice to get to endurance fit, healthy and ready to race. As a practitioner for over 20 years, working with endurance athletes and having competed myself in IRONMAN competitions, I am always amazed at how little attention some athletes put into their fuelling plan. Successful race day nutrition is a combination of science, practice and a bit of an art form, too. Ideally, your nutrition plan will have been fine-tuned with sufficient training in the weeks before the race. So, the day itself will just be a continuation of what you know works for you.

Carbohydrate needs

How much carbohydrate you need during an event depends on you - your body size, personal preferences and the length of the event. In endurance events that last longer than three-plus hours, choose between 60-90 grams of carbohydrate1. Remember, though, that if you consume more than 60 grams per hour, it is best to use a number of different forms or carbohydrate (your body can only absorb a maximum of 60 grams of glucose per hour). So, a combination of sports drink, gels, chews and other solid foods can quickly help you meet this target. It is essential to trial how much carbohydrate per hour that works the best for your digestion. Start slowly and work up to the maximum amount you can tolerate.

Are you fat adapted?
If you are fat adapted, you will need slightly less carbohydrate per hour, but you'll still need to calculate and practice to find the right amount for you. Many fat-adapted athletes I have worked with find that about two-thirds of what they used to ingest when not adapted is about right. But this, like all sports nutrition, is very individual.
Before 60-90 grams carbohydrate per hour recommendation, many athletes would use their body weight in kg as a guide as to how many grams of carbohydrate would be needed per hour. Thus, for a 70 kilogram athlete, 70 grams carbohydrate per hour might be trialled. As a nutritionist, I still like to use this as a starting point and go lower or higher depending on athlete feedback, their energy levels and digestive comfort. It is important to note that the longer the event, the potential for dehydration and the point at which digestive function may start to suffer.

Varied intake
Many athletes I work with consume the most substantial amount of carbohydrate on the bike leg of a triathlon and then drop their intake by 10-15% for the run section for digestive comfort. Similarly, some people prefer a combination of solid foods, gels and sports drinks on the bike moving onto liquids only (such as cola, water, sports drinks and gels) for the run.

Fuel choices
What you choose to eat during racing is as individual as you are. Practising with food during training before the event is vital - never try anything new on race day no matter how great it sounds in the advertising. And, always be flexible about adjusting your plan/intake depending on race conditions and how your body feels.
Most people choose a combination of carbohydrate gels, sports drinks and food during endurance events. For events lasting longer than four hours, consider a small sandwich, banana, some dates, jelly lollies or a sports bar.
In general, the foods you choose during a race should be high glycaemic index - they need to be digested quickly and fuel the body fast. Keep protein, fat and fibre to a minimum (they slow down absorption rates). A small amount of protein is often well tolerated and good for keeping blood sugar levels more stable. If you are fat adapted, you'll probably choose to eat a bit more fat and protein if you have tolerated it well during training.

If you are racing a HALF IRONMAN
You may be able to cope with slightly less carbohydrate per hour due to the shorter distance and you may be going faster, too. Thus your digestive function may be more compromised. Practising the kind of intake you need for each distance is important.

Digestive issues

If you are prone to digestive upsets, bloating or diarrhoea while racing, there are a few nutrition points you need to consider to avoid too much time spent in the portable bathrooms by:

1. Knowing your fuel and fluid plan per hour in advance.
2. Being flexible with your plan depending on how you feel.
3. Limiting fibre intake (oats are a favourite food for triathletes but if you are prone to gastro issues while racing, you may want to re-think them as they are high in fibre).
4. Watching your protein and fat intake, or having practiced the tolerable quantities beforehand.
5. Knowing the fluid/water intake you need per hour and adjusting it depending on heat/cold weather conditions.
6. Not over hydrating; this can be as dangerous as dehydration.
7. Never ingesting food, gels or sports drink together - this may lead to a concentration of carbohydrate that is too much for your stomach to cope with and impede the rate of gastric emptying.
8. Only consuming gels and food with water.
9. Not consuming sports/electrolyte drinks that contain carbohydrates with foods and gels.
10. Calculating fluid needs per hour for your race pace. Sweat rates are not standard, see for more information on fluid needs, sweat rates and sodium intake.

Remember, sodium and electrolyte intakes are vital during racing, and using gels, sports drinks, foods and electrolyte tablets can meet your needs. Many athletes aim for approximately 500mg sodium per hour or slightly more, but this also depends on the individual. So, practice during training.

And, no matter your choice of foods or fluids, it is best to consume them at a set schedule to decrease the chance of gastrointestinal upset. A good starting point is to ingest your carbohydrate along with sufficient water every 20-30 minutes while racing. Be aware that gels and chews must be consumed with sufficient water to be absorbed rapidly. Sports drinks are premixed at a ratio of 4-8 grams of carbohydrate per 100mL of fluid as this is a volume that is rapidly absorbed across the intestinal lining. Never consume sports drink with gels or solid foods as this will cause what is generally known as a 'stomach plug' which means your absorption ability has been limited. Factor in your fluid needs per hour which you need to take into consideration when designing a race plan.

The race plan
So, what does all this look like in a race plan? Here is a sample plan for a 65-kilogram athlete racing IRONMAN using a variety of food, drink and carbohydrate sources.

Pre-race breakfast 1-4g carbohydrate per kg body weight.
2 hours before race start
65kg athlete aiming for 2g per kg = 120g carbohydrate with a small portion of protein and fat.
15-20 minutes pre-race 1 gel plus water or 300mL of sports drink.  
Swim Try not to drink the ocean/lake.  
Transition from swim to bike Sip water only for 10-20 minutes. Flush out salt water and let body settle onto the bike.
Bike 60g carbohydrate per hour plus a small amount of protein and fat if solid foods are ingested like bars etc. Sports drink, gels, dates, bananas, sports bars, sandwiches and other chosen foods.
  Ingest 20g carbohydrates every 20 minutes or 30g every 30 minutes. Set the timer on your watch to beep every 20 or 30 minutes.
Fluid intake as calculated per individual.

having gels or solid food.
Have sports drink by itself. 

Don't forget sodium/electrolyte needs via sports drink, gels, electrolyte tablets and foods.

Run May want to decrease carbohydrate intake or not. 50-60g per hour Sports drink, gels, foods, fruit, lollies and cola
  Fluid intake may drop slightly due to difficulty ingesting while running but is still important! Water, sports drink, cola.


Before you race, make sure you:

1. Work out a race plan.

2. Practice it.

3. Make adjustments.

4. Practice it again.

5. Measure carbohydrate intake per hour/and other foods.

6. Measure fluid, sodium/electrolyte needs per hour.

7. Bring your own foods/ensure foods are prepared.

8. Organise foods and snack size portions.

Do not change your plan because someone gives you a free product. And, most importantly for race day, enjoy the day you have worked so hard to get to and be willing to make adjustments to your nutrition and fluid plan depending on how your body feels.