Ironman Race Nutrition Plan

I’m 2 weeks away from my first Ironman and I’m a bit worried about my nutrition plan. I’ve trained with the Enervit energy bars / liquids, which will be available during the event, and I’m comfortable with it - I’m eating way less calories than recommended though.

Here is what I do on long sessions:

  • bike:
    • 1 energy bar every 1h (106 Calories)
    • around 400ml of isotonic drink (about 85 Calories)

Assuming I’m doing a bit less than 6h (I will aim around 5h30-5h30), this gives 6*191=1146.

  • run:
    • 1 energy bar every 1h (106 Calories)
    • around 300ml of isotonic drink (about 65 Calories)

Aiming for 4h, it gives (I don’t count the last hour) 3*171=513.

This is only about 1650 Calories total, and definitely less than 250 Calories / hour, which I read everywhere is a lower bound of what I should eat.

That being said, on 5-6h workouts, I’m comfortable with this - I’m quite hungry at the end but not excessively. I feel like I can increase the intake and eat 1 energy bar every 45 minutes (tested it already - works OK), but I didn’t found it necessary nor improving my pace.

I’m planning to stick with current plan, but I’m just fearing than on a full Ironman distance I will lack energy towards the end. Common fear I guess… Any thoughts and experiences appreciated !

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This is part of the “science experiment” that is Ironman racing, the optimal thing is to do as you’ve done - train your race day nutrition before race day.

The common approach is to consume 60-100g carbs/hour (this is measured in carbs only because you won’t really process fat you consume on the day in time to use it unless your are already training fat-adapted).

People don’t discuss this much but it’s worth considering your own exertion rate if your intensity factor is at the top of bottom of what’s recommended at IM distance.

Ironman races tend to provide around that at each station, but you need to be aware that bottles will not always be full, and mixes may be weak or strong, and bars are often provided in halves…and High5, 226ER and Powerbar all have different carb content. :sweat_smile: (36g, 45g, 44g)

Then you need to take into account weather, particularly heat and wind which dehydrate.

At Ironman Lanzarote on the day my pace was slow, the bottles were on average just over half full and the coke was weak, so I necked the coke at the station, grabbed two half bars/bananas and put the electrolytes or water in the cage. Probably got me to around 70-80g of carbs, ~800ml fluid per station.

I think we had a chat in the other thread as I was concerned too - it is absolutely a common fear. My last race was the only full distance I think I got it relatively right.

You can’t replace everything you burn at the rate you’re burning it, so you have to be continually topping up a bit as you can’t catch up…worth having a gel in T1 and T2, and carrying a spare bar from T1 in your jersey.

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Thing with Ironman is that after the swim you have to ride a bike and after the bike ride you then have to run a full marathon. It’s quite easy to do 112 mile bike ride on a reasonable amount of half-arsed eating and be able to finish it ok. The trouble here is that you really need to finish the bike ride ready to go and run 26.2 miles…

I would plan on aiming for 80g of carbs per hour. That is like 2 bars or 4 gels.

Practice this beforehand as it’s a lot for your stomach to get used to…

By the look of it it sounds like you should take a bit more calories in the bike. The rule of thumb is 200-300cal/hour with 60-90g of carbs/hour and it is in the bike that most people buffer for the day.
Also, don’t get too focused in calories intake and forget about sodium and electrolytes. Make sure that whatever you’re taking will have enough minerals.

That’s what I like to hear, because switching things up now is just asking for a disaster. I personally get in around 400 Cal/hour but I’m bigger and have trained that for the last couple years and did my first IM on around 250 Cal/hour. Don’t get all worked up reading things on the Internet. You put in your training, you did the long workouts, you’re going to be fine.

Seriously my biggest piece of advice to you is to disconnect from the Internet for the next two weeks (at least in terms of reading triathlon forums/blogs/websites) and remind yourself that you’ve got this.


While there are some general guidelines like many things it can be very individual. I tend towards the lower side of the nutrition and probably isn’t that different to what you are planning to do.

For my last IM during the bike I had 5 gels, 1.5 Clif bars and and a half and a pack of jelly babies which works out at around almost exactly the amount of calories you are taking in and around 55-60g carbs per hour.

On the run I used 3 gels over duration and a couple of mouthfuls of whatever energy drink was available at each aid station and a bit of coke towards the end. In my experience the IM marathon really just about survival so while you have a plan be prepared to be flexible with it if your original plan isn’t appealing at the time!

@JoeX is right that the intensity you are racing at will dictate to a degree the number of calories you need as well as how you plan to take them in - the higher the intensity the less likely solid foods are less likely to be digested easily and your weight will also play a part. A 60kg athlete who rides round on relatively small watts will burn through far fewer calories than a 90kg athlete who needs much higher power for the same ride.

One other thing to bear in mind is that if you under fuel and bonk it’s fairly easy to get going again after taking in some form of sugar. If you over fuel there’s nothing to do but to slow down and allow the body to digest the food that’s already been ingested and that’s not a quick process.

Trust your own plan and experience if you’ve practised it and if it doesn’t work out, change it next time.


Thanks ! That sounds like a great advice to me and that’s what I will do :slight_smile:

Thank you all for the advice - I appreciate a lot.

I’ve did a small test, on a 2h workout (1h30 bike, 30min run) with a bar every 30mins and it worked pretty well - no problem ingesting it, nor stomach pains on the run. But it was a short workout so not really significant.

I’m sticking to initial plan (knowing myself, I will probably be too tempted to eat a bit more, so it will end at 1 bar every 50 mins or something :slight_smile: )

There is good recipe for dinner & supper
low calorie and tasty do not be afraid for weight))

Been here. It’s awful. GI distress, walking on the run, bloat, the whole 9. Go with what’s worked in training. If it doesn’t work in the race, you’ll know better next time. But changing things at the zero-hour is a recipe for disaster. Good luck!

If you choose to do a second Ironman and for others here is what I do for reference. I’ve played around with different ratios of liquid, gel, and solid food over a couple of Ironman’s with lots of cracking but never really any stomach distress. In training I like to choose more intense race pace like rides to test what kind of product agrees with me and how much of it I can consume. The run portion is usually where I fall apart nutritionally and am trying to iron out. I like to go with something as follow though.

Pre Swim:

Gel and sip on some diluted drink mix.


Setup includes hydration system on the aerobars, 1 water bottle holder behind the seat, and small storage compartment on the top tube as the Felt IA series provides.

Water only between the bars.

Powder or big serving GU gel bag (15ish gels worth) divided between 2 bottles giving around 750 calories per bottle. Freeze bottles night before. 1 goes in special needs other goes into rear bottle holder.

In storage couple favorite bars of whatever I’m craving, last race was 2 Bonk Breakers cut in half for easy access, 2 caffeinated gels. More solid food and gels in special needs if needed - dropped, hungry, or whatever other reason.

Throughout the ride sip on the rear bottle followed by sipping on water. Try to ration out the bottle throughout the first half, if wanted you do dashed timing markers on the bottle to see if you’re on track. Solid foods are also spread throughout the ride. I try to rely moreso on liquid/gel rather than solid if possible. At special needs replenish everything.

Total Calories

Liquid: ~1500
Solid: ~500
Gels: ~200

Total: 2200+ for a bit over 5hrs got me off feeling pretty good.


Couple gels in the tri suit and then a free for all at aid stations. As mentioned this has caused some cracking issues.

In the future going a flask with ~400 cals with some Maurten gels in the trisuit and at half way needs bag if needed

Best of luck on your upcoming race!