Ironman Triathlon Calorie Expenditure

Based on a triathlete who weighs 140 lbs (10 stone) the following are the data for an Ironman Triathlon calorie expenditure.
This all depends on the size of the triathlete so calorie requirements can vary considerably by up to -/+ 20%.
Swimming 3.8km
Estimated finish time 55 minutes - 495 calories
Estimated finish time 60 minutes - 540 calories
Estimated finish time 75 minutes - 675 calories
Cycling 180 km
Estimated finish time 5 hours 10 minutes (22mph) – 5,580 calories
Estimated finish time 5 hours 36 minutes (20mph) - 5,376 calories
Estimated finish time 6 hours 40 minutes (17mph) – 5,200 calories
Estimated finish time 7 hours 45 minutes (15mph) – 4,650 calories
Marathon 26.2 miles
Estimated finish time 3 hours 15 minutes – 3,120 calories
Estimated finish time 3 hours 45 minutes - 2,900 calories
Estimated finish time 4 hours - 2,800 calories
Estimated finish time 4 hours 30 minutes - 2,700 calories
Estimated finish time 5 hours - 2,600 calories

Things to consider.
The following will affect the number of calories that are used.During an Ironman triathlon marathon 26.2 miles your calorie requirements will depend not just on the distance but the speed and your efficiency during the last section of the triathlon. If you are tired you run slower and as your form becomes inefficient you sue up more calories to allow you to move forward. In theory you need the same number of calories to run each mile. Running faster however requires more energy hence the difference from a faster to a slower marathon.

How can prepare for an Ironman triathlon?

Training for the Ironman.
You will need to listen to your body more.The main reasons for getting injured, over training or becoming ill are increasing intensity too quickly, mixing long slow distance with fast intensity running.
Ignoring the signs of fatigue, by having an easy day rest day improvements will occur.
There is no such thing as a rigid training schedule.Why? If you are able to stick to it doing exactly what is required never missing a session (Not an ideal world due to distractions etc) then the training plan is not taxing you enough, it's all about find your limit, what may seem hard now could be easy in a few weeks time.
Outside factors effect this like, quality sleep, free from infections stress, quality recovery time, good food (That is ideal for you) as everyone is different and this changes throughout a year.
Mistakes are much less important in training start making them now and learn by them, too little or too much food and how this effects your performance.
The Key Factors to give you peak performance on race day need to be improved all the time.Mental & Physical Toughness, Exact Muscular endurance sessions. Important Back2Back sessions for Ironman, Intensity and Frequency with Feedback. Eliminating errors in training, Progressive Training, Injury prevention, Equipment considerations, Delaying Fatigue, Heart Rate Monitor Training, Race Pace practice.

Time efficient training- you will need to train longer hours per session but not twice as much as a half Ironman for example. Fine line training reduces the chance of over training by doing hard easy sessions in the same week, Total rest days lets your body tell you if something is wrong or likely to happen not by training easy.50% of your Ironman time will be on the bike make sure you spend 60% of training time in the next 6 months on the bike so you are fresh and able to run to your potential.
It’s Ok to spend more time swimming and running December-February? March but then you have to change the way you train. Total fitness also involves core strength when you get tired in training then racing you will draw off these reserves, tired during the bike or run small climb or into a head wind, use that core rather than fitness, this will save your energy levels for longer into the Ironman.

Swim a minimum of 3 times a week even if the total time of only 100 minutes, you need to keep the feel for the water and keep those swim specific muscles firing.

Cycle- Build the miles don't take chances with windy icy days. If you had 24 weeks to build to maximum long bike ride 4-6 weeks before Ironman and started at 30 miles on week 1. Then add 4 miles each week your longest ride would theoretically be 124 miles, this is a simplistic straight line, whereas the line should be up and down with a differential of +/- 15% the week before a long ride drop back 10-15%.

BACK TO BACK SESSION - The Mid Week Back to back session slightly above IM pace Long rides 50% on your own easy, learn to eat and drinks lots watch your heart rate monitor.

RUN - The Long slow distance that MUST BE at predicted Ironman pace. Eat and drink every 20 minutes and monitor your recovery see how much better you feel 2/3 days later. This will get you use to running slow and will strengthen your legs, running slower is actually harder!! Run off road to save your tired legs and build up resistance strength.
Slow recovery runs can be done after a bike ride. Back to back sessions. My suggestion is only ever run up to 60% of the time you cycled before doing a back 2 back sessions. I.e... 50 minute bike 30 minute run or 140-minute cycle 60 minute run. A minimum of eight back 2 back sessions per month during certain phases of the build up are necessary.