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Fueling During A Half or Full Ironman Distance Triathlon

Nutrition for 70.3 and 140.6 is super critical for maximizing performance. I always say “don’t let nutrition get in the way of your fitness or competition, like finishing an Ironman strong”. With regular practice and experimenting with what and how much you need to fuel during your longer bike, runs, and brick training sessions, then using that information to develop your nutrition plan for competition, leaves NO guess work on race day.


If possible get your sweat rate tested. After my visit to the Gatorade Sport Science Institute in 2007, I found out that I don’t have a lot of sodium in my sweat and can get all I need from Gatorade. I also learned that I was ingesting too many carbohydrates, 1 power bar plus gatorade and water to total about 400 calories / hour. Based on the sweat rate test, I was able to dial in my nutrition plan to 200 calories and 40 ounces per hour. 1 gel plus 20 ounces of water and gatorade.

Keep it simple is the name of the game when it comes to Ironman Race Day Nutrition

  • When you log your  training, include a log of your  nutrition next to it. Include how you felt and continue tweak it if something is not dialed in.
  • Plan the details of your fueling strategy in advance. Will you rely on aid stations or your own supply? Will you take advantage of the special needs bags that you get around the half way point of an ironman and mile 18 of the run?
  • Liquid calories are easier to digest then solids and if you tend to get a nervous stomach race day try out varies products in training.
  • When planning out the time between when you eat breakfast and when your swim start is, if is important to have some calories if your wave start is more then 3 hours after breakfast. Decide if you will consume an energy bar, gel, sports drink to top off  your energy tank as race start gets closer
  • Keep a log of  how many calories you eat before and during for your longer workouts
  • Research recommends an intake of 40-60 grams of carbohydrate, or 150-250 calories per hour. I recommend starting with 200 calories and adjust it based on their body size/weight. Smaller athletes may need 100-150 calories, larger athletes as much at 450 / hour. Take to a local Registered Dietitian.
  • Dialing in your pace/power/heart rate on the bike will affect your nutritional needs which will impact your run. Even if you follow your planned number of calories, if you ride too hard, you will struggle in the run. So be mindful of pace and nutrition while training.
  • Liquid vs solid is a personal preference and I have done both over the years with no GI distress. If you relay on solids, do so in the early stages of the bike course. I like to break a sport bar in 4 pieces and eat one every 15 minutes and drink water with it.
  • Eat your solids, if any, early during the bike (first couple of hours). Aim to keep the rest of your fuel intake liquid.
  • Food of choice: Find the brand of bar and gels you like, and get used to using them. Remember, gels and bars are only one option — dates, PB&J sandwich, snickers, coke and bananas are another. Find what works for you!
  • After you find what you like, stick to one brand of electrolyte drink and one brand of sports bar or gel.
  • Travel with more then you need.  You don’t want to be buying different brands the day before the race.
  • Rely on an electrolyte drink throughout the day and keep water intake to when you eat dense carbohydrate sources (gels, bars, cookies, etc.), because mixing electrolyte with food will only make the solution denser.
  • Never skip and aid station on the bike or run. Grab water, sip it, dump it over your head if the conditions are hot to cool off
  • If you get stomach trouble, slow down! Your problems will resolve if you give your body the chance to recover. You can cruise easy for 10-15 minutes and only “lose” a couple of minutes on the day, or you can continue to carry on hard and lose hours!! Or worse, DNF!!
  • With practice will have your race day breakfast, before your wave start and during the bike and run portion dialed in

A nutritional strategy for race day should be simple and right for you. Make every long training session a practice run-through of your IM fueling and pacing. By the time race day rolls around, it should be second nature what you eat and drink.

It is important to know what your body needs and that will vary from person to person. It is important to practice.
Author: Wendy Mader is the co-founder and owner of T2Coaching and has made a lifelong commitment to fitness, sports, coaching, and triathlon. From her youth as a competitive swimmer to her current career in the fitness industry, her dedication shines. Wendy is a former collegiate swimmer and has 25 years experience in triathlon including 15 Ironman’s. Wendy is also an Ironman University Certified Coach, an 8x Kona finisher and author of “Ironman Training For Beginners.  Wendy recently moved to Georgia with her husband and dogs after nearly two decades living in Colorado.

Post Author: Dave Erickson