Study says non-elite marathoners fuel at 21.7g of carbs an hour
The race-day gap is not physiology, it is how little actually gets swallowed.
Non-elite marathoners take in an average of 21.7 grams of carbohydrate per hour on race day. That is the headline number from a 2025 study by Lanpir and colleagues, flagged by sport scientist Jonah Rosner (@jonisportsci), who measured it against the usual advice of 60 to 90 grams an hour.
21.7 grams is not even half the low end of that target. Rosner says the pattern in the data is that athletes both under-consumed and overestimated what they took in. In other words, runners are eating less than they think, and a lot less than the number they would quote you at the start line.
What the target actually is
Rosner's own guidance for race efforts over two and a half hours is 60 to 120 grams of carbohydrate per hour using a glucose and fructose blend (two sugars your gut absorbs through separate channels, so combining them raises total delivery compared with glucose alone). Most runners land in the 60 to 90 gram range. He says the upper end, up to 120 grams, is mostly for elites and the highly experienced, and he cites SiS-funded research by Ravikanti and colleagues in 2025 that found elite marathoners can use up to 120 grams an hour with improved running economy.
For context on how fast those numbers are moving, we covered a earlier study arguing 100 grams an hour beats 60.
The fix is a scale, not a bigger number
Brady Holmer (@brady_h), sharing the thread, put it in one line.
The practical point is that a 21.7 gram average is a behavior problem rather than a gut-capacity problem. Rosner's advice is to pre-plan every fueling window mile marker by mile marker, and he lists three mistakes to avoid, waiting too long to start fueling, trying anything new on race day, and ignoring individual variation in body weight, pace and temperature.
He also says to pair gels with water rather than sports drink so you are not overloading your gut with carbohydrate from two directions at once. On product, he notes SiS BETA Fuel gels carry 40 grams each in a 1 to 0.8 glucose to fructose ratio, so two an hour gets you to 80. He is clear that none of this gets invented on race morning.
What it actually means. The gap between what runners say they fuel and what the research measures is large enough that chasing 90 grams an hour is pointless until you have weighed and timed what you actually swallow on a long run.
This is why you gotta measure your carbs, people!
race-day nutrition is not invented on race morning. It's built in training.
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