Ask Stacy: How Do I Fuel for Longer Distances?

Fueling is key when it comes to “going long”—here’s how to get it right with expert advice from Dr. Stacy Sims.

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Although races might still seem like a long way away, practicing your race nutrition in training is key to getting it right on the big day. There are many things to consider here, but the main concept is that the body’s ability to absorb fuel changes with the duration of exercise. When you approach fuel for longer distances, it’s best to think about your fuel in stages: What do I grab in T1 to help me recover (partially) from the swim? What do I eat in the first half of the bike to help fuel me for later? What do I eat when I feel I can’t stomach anything? What do I have in T2 to help get my legs under me—and what do I consume on the first third, middle third, and last third of the run?

Remember that a full Ironman is a completely different beast from a 70.3 when it comes to your fuel. While you can typically get away with poorer fueling habits when racing a 70.3, having a good back half of a full-distance race means you need to nail some important strategies to help your body as it becomes increasingly stressed from metabolic demands. Here is a brief outline to get you started:

How to Fuel for Longer Distances

  • Fluid intake goal per hour on bike and run: a minimum of 16oz, a maximum of 2 x 20oz bottles of functional hydration (e.g. Nuun Performance). Note here that for longer races, drinking just to thirst may not be optimal as there are inherent biochemical changes that occur while exercising that will mute our thirst. The best way to determine what your fluid needs are is to do some bio-hacking using pee sticks and experiment a lot in training—figure out what works for you. We are all unique here. 
  • Calorie intake goal per hour on bike: 3-3.5 food calories per kg of body weight per hour (you can afford to eat more on the bike, but not on the run due to higher impact). Based on a projected body weight of 135 lbs, this would be around 180-210 food calories per hour (this does not include hydration mix calories).
  • Calorie intake goal per hour on the run is ~2 food calories per kg per hour, (for 135lbs it is ~120calories per hour). For the first third of the run, ideally you want to eat a bit of solid food (e.g. soft bars, figs, smooshed soft pretzels), then move to chews/soft jelly candies, and for the last four to six miles, use glucose tablets and cola, where the goal is to keep blood sugar up—it is no longer about digesting fuel.
  • Solid food ideas: protein bites, mini protein-power cookies, white bread peanut butter and jelly sandwich bites pinched into balls, small salted potatoes, Bounce energy balls.
  • Semi-solid food ideas: energy chews, jelly beans, glucose tablets, fruit chews.

Remember that you never want to try to eat a lot at once: sip sip, nibble nibble goes very far here! Be sure to test everything thoroughly in training (in key longer duration sessions) and aim to mix up what you’re consuming to help minimize the potential for nausea and gastro-intestinal problems.

Featured image by Neil Kerr/Getty Images

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