What are the nutritional recommendations when training and competeing in Ironman?

Hi Rhett,

If you're doing the full Ironman - 2.4 mile swim, 112 mile bike and full marathon, then you'll probably be training at least 5 days per week and probably at least 1 hour per day (some days longer, some days no training). I can further assume that an average daily training session would have you burning the best part of 1000 calories.

Generally, the first thing I do to quickly calculate requirements is multiply your weight in kg by 2-3 to get your protein needs in grams (2 would be minimum), then multiply by about 0.9 to get your "minimum" fat recommendation in grams. For carbs, you would multiply by from 6 to 8. If you go with the higher protein recommendation and you like to eat more fat, then closer to 6. If you like your carbs, go closer to lower protein recommendation and keep fat near to the 0.9.

Example - 80kg person:
3 x 80 = 240
0.9 x 80 = 72
7 x 80 = 560

So that's about 3850 calories. Some people would need/want more than this but this is probably pretty close to what a lot of triathloners actually eat. Certainly add more calories if you are losing weight or you feel your blood sugar is going low during training and if you are having trouble getting in this many calories remember, as long as your diet has a good amount of fruit, veg, meat, fish, dairy. etc, it's fine to add some junk like crisps/chips, Mars bars, etc.


Some official recommendations don't recommend quite so much protein and/or recommend higher calories and carb intakes but my experience with high-performance athletes is that they usually don't eat as much as the recommendations suggest and I find that the higher protein helps with recovery, minimizes injuries and can help with better glycogen storage if used correctly.

For the day of the race, if you are a fairly organized and motivated person, you can carb load, which requires depletion of carbs about 3 to 6 days from the race and then re-introduction of the high-carb diet but with about 50% extra carbs per day in the last 3 days. If you try this, feel free to ask a new question and remember to only eat carbs that your body tolerates well.

As far as what to eat prior to the race, go for a very high carb meal the night before the race (eat as much pasta or rice or similar as you can comfortably handle but nothing high in fibre or anything), lower in fat and with a good source of lean protein. On the morning, again, high carb meal that's easily digested, with lean protein (depending upon when the race starts).

As far as drinks and gels, learn which one works best for you in training and go by the rule of thumb that you should start drinking an isotonic sports drink (gel, whatever) every half hour or so in the race starting at the first hour into the race. A drink is best if you are racing in a hot environment.

This diet is specifically for endurance athletes.