Ironman nutrition: plan for success and nail the fuelling

Make it memorable for the right reasons with our advice for the bike and run legs


Going long this year? Make your Ironman memorable for the right reasons with these tips on how to organise your nutrition on the bike and run legs of a long-distance triathlon.


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Bike leg

Aim for 200-600 calories per hour on the bike (says coach Mark Kleanthous). If you have any special preferences/dietary requirements keep extra food in your transition bags.

Throughout the bike ride aim for 1,000mg of sodium per hour. You need to adapt your race-day strategy to the climate/conditions and what works best for you at Ironman race pace.

Mentally divide the 112-mile bike ride into 3 x 30-mile segments and the final 22-mile section then follow this strategy:

0-30 miles

Drink only water for the first 15-20mins after beginning the bike section, then consume calories every 15-20mins. This first segment is about fuelling up again after the swim and preparing for the miles ahead. This should be the easiest section of the race.

30-60 miles

In this segment focus on consistent calories and hydration. During the tougher terrain focus on consuming liquid calories and then switch to solids for the easier parts.

60-90 miles

If you’ve fuelled well you shouldn’t feel weak or tired. If you do then slow down and consume more. If you’re feeling energised and strong, still hold back until the final 22 miles. During this segment you will need to urinate. If you don’t need to then you’re dehydrated and need to drink more.

90-112 miles

If you’re having mood swings this is likely a sign you’re running low on calories. If you don’t feel like eating ease back and consume more calories. Stick to liquids if you feel tired or weak.

Stay focused as it’s easy to forget your nutrition at this stage. Judge the final 22 miles depending on how you feel, and avoid paying too much attention to just heart rate alone as this can be misleading.

Run leg

Fuelling right for the run can sometimes prove quite challenging as you will be trying to manage dwindling carb stores, taste fatigue and what you can stomach (adds Rin Cobb, a clinical and sports performance coach).

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Here are some pointers to help you go the distance:

1. Carbs are your priority. They are your main source of fuel, but as you’ll have been on the go for many hours by this stage your reserves will be low. Aim for up to 60g of carbs per hour, but if using a mixture of glucose and fructose, 90g per hour is optimal. It’s worth practising eating in training to help the gut adapt to this volume, which will also prevent tummy troubles.

2. A steady supply of carbs will also help to keep your blood sugars in check, thus reducing your chances of hitting ‘the wall’. Those that have experienced this won’t forget it in a hurry; prevention is definitely the key.

3. Try experimenting with real food options, as these can actually be cheaper and also meet your needs. Good foods to try are flapjacks, cereal bars, Jaffa Cakes, fruit  (fresh and dried) and that old faithful, Jelly Babies! When perusing the supermarket aisles, look for total carbs per 100g rather than just calorie content, and avoid products that are high in fat and protein.

4. Sports drinks are a great triathlon fuelling option if you’re struggling to eat enough. They help your body absorb fluid better than just water alone, plus the salt encourages you to drink more without overhydrating.

5. You could also try caffeine, which can reduce fatigue towards the end of a race. Timing is important as caffeine can take 45-90mins to take effect; like all aspects of your nutrition strategy, test it in training beforehand.

So in a nutshell: think carbs and practise your nutrition in training to ensure you get the most out of your programme. Bon appetit!


For lots more performance advice head to our Training section