By now, it’s more or less common knowledge that you should “fuel” during marathons and ultramarathons by taking carbohydrates. For marathoners, this means sports drinks, energy gels, or energy blocks; for ultramarathoners, “real” food like granola, pretzels, potato chips, and peanut butter sandwiches are popular as well—your stomach can only handle sugary syrup for so long.
Knowing that you should fuel leads, naturally, to an obvious follow-up question: how much should you be fueling? In other words, what should your fueling rate be? I’ve been digging into the research on this question lately as it applies to carbohydrate intake.
For a long time, the default recommendation from sports nutrition experts has been 60 grams of carbohydrates per hour (60 g/hr) for events lasting two to four hours [1].
This is still a reasonable starting point for first-time marathoners, but I want to cover some of the latest developments on fueling, and especially the concept of multiple carbohydrate fueling—consuming sources of both glucose and fructose to sustain a higher rate of fuel oxidation.
Multiple carbohydrate fueling is the key to understanding why very long races like ultramarathons (as well as long cycling races, like Tour de France stages) have seen major breakthroughs from the more systematic application of scientifically-based fueling strategies.
