The Top 8 Race Fueling Mistakes Made By Ironman Triathletes

Pin it

Couer D' Alene Ironman commenced this past week. As a triathlon coach, I have a myriad of athletes competing in the race. Some did well. Others struggled.

But with each athlete, a few days after the race (before post-race amnesia sits in) I sit down with a notepad, via phone, text, or face-to-face, and discuss the highs and lows of their long day.

Believe it or not, 99% of my coached athletes that did Ironman CDA performed their race day pacing *exactly* as planned. Unfortunately, close to half “fumbled” on the fueling, and it came back to bite them.

Here are the top 8 fueling mistakes that they made, and the lessons you can learn.

#8: Not adjusting salt intake to weather. Ironman CDA was cold, wet and windy – but hot for several weeks leading up to the race. As a result, many athletes were prepared with race day fueling plans that including several electrolyte capsules per hour or “pre-mixed” salt in their drinks. But without the anticipated amount of sweating, they experienced bloating, water retention and upset stomachs. Lesson: be flexible with your salt plan.

#7: Not accounting for water in liquid calories. Do you mix your calorie in powder form with water, or get it pre-mixed? Although you should be taking in the equivalent of 1-1.5 bottles of water per hour, this *includes* the liquid that you take in from these calorie sources. Two athletes forgot this fact, and ended up with an extra 16oz of water per hour, and the subsequent stomach distress and sloshing! Lesson: calculate how many ounces of water are in your liquid fuel, or use solid fuel (i.e gels/gummies) and plain water.

#6: Getting tired of their chosen fuel source. Sure, you practiced with your brand of choice for 5, 6, 7, maybe even 8 hours during training. But did you plan and prepare for how many gels you'd want at 10 hours? 11? 12? If you're not ready for the time in Ironman when your body says, “ENOUGH ALREADY OF THE LIQUID SUGAR!”, then you can crumble, and begin grabbing other fuel sources. Sources you haven't practiced with. And sometimes the stomach doesn't like that. Lesson: Ironman is not a buffet restaurant. Stick to your fueling plan, have iron-will and self-control.

#5: Losing track of what was eaten. As I rode my mountain bike around the Ironman run course, I would occasionally shout out to athletes, “How much have you eaten/drank?” Often the response was a shoulder shrug or throw-up and confused hands. If you want to have zero guesswork in Ironman, you must know, at any point in the race, exactly how much you have eaten and drank. You cannot turn your brain off and just shuffle along. Lesson: math, math, math. Add up those calories, and break it up between swim, bike and run, which leads to #4…

#4: Not replacing calories/salt/water loss from the swim. You're out there exercising for 1 to 2 hours. In normal circumstances, you wouldn't get out and walk away without replacing all that fuel you burnt, salts you sweated and water you lost. This is asking for an early bike bonk. Lesson: in the first transition tent or in the first 5 minutes of the bike, make sure that you eat as many calories, electrolytes and water *as you would have consumed had you been able to eat while your were swimming*.

#3: Eating too much before getting off the bike. Several athletes experienced sloshing, gurgling, and gassy guts within a mile into the run. There are two reasons for this, and the first is obvious: eating or drinking too much on the bike. The second is not so obvious: eating or drinking too much in the last 30-40 minutes of the bike. Lesson: taper your calorie and water consumption in the final 5-8 miles of the bike to as little as possible to avoid a full gut feeling on the run.

#2: Forgetting to eat during the run. This completely destroyed the marathon for one athlete. Getting carried away with what started off as a fantastic race, he set his pace and got into his zone on the run, and began hammering away excellent splits. He ran through every aid station focused completely ahead. And at 10 miles, he crumbled. Lesson: no matter how good you feel, remember to eat. Do not fear the almighty gel.

#1: Mixing sugars. This was the biggest mistake and caused more trouble than anything else. Without getting into the science of it in this post, let's just say that fructose sugar is “selfish” and very easily competes with other sugars for transport from the small intestine into the bloodstream. Consumption of a pure fructose beverage with other long-chain sugars (i.e. Maltodextrin) typically found in gels will draw extra water into the GI tract and can cause stomach upset and diarrhea, especially if you haven't trained with fructose sugars. Athletes who had never taken Gatorade in training took a sip here and there on the bike, and 80 miles in, they were hunched over their aerobars with twisted stomachs. Lesson: stick to one fuel source as much as possible, and preferably one “type” of sugar.

It is now my job as an Ironman triathlon coach to sit down and create a roadmap for these athletes that ensures the same mistakes are not made twice! Please learn from their errors, take some notes, and have a smart and enjoyable race. Just shoot me an e-mail if I can help, or check out the new book, “Holistic Nutrition for Ironman Triathletes”, over at

Ben Greenfield is recognized as one of the top fitness, triathlon, nutrition and metabolism experts in the nation. In 2008, he was voted as the Personal Trainer of the Year by the National Strength and Conditioning Association (NSCA), an internationally recognized and respected certifying agency for fitness professionals. Ben hosts the highly popular fitness, nutrition and wellness website at, which features a free blog, wellness podcast, and fitness product reviews from Ben. Pacific Elite Fitness ( is an online portal where Ben coaches a wide range of triathletes and assists people from all over the world with personal training for nutrition, fat loss, muscle toning, and general fitness. Ben also oversees the physiology and biomechanics laboratory at Champions Sports Medicine ( which offers metabolic-based weight loss, bicycle fitting, running gait analysis, swim stroke analysis, VO2 max testing, blood lactate testing, resting metabolic rate analysis, and other cutting-edge procedures for weight loss and human performance. Ben holds bacheler's and master's degrees in exercise physiology and biomechanics, and is a certified personal trainer, strength and conditioning coach, sports nutritionist, and bike fitter.


Log In or Create an account