2:09 marathoner Tom Nobbs fuels at 114 to 120g of carbs an hour

Thomas Nobbs, a Canadian pro with a 2:09 marathon best, laid out his fueling on episode 500 of Zach Bitter's podcast, and the number is 114 to 120 grams of carbs an hour on long runs and quality sessions.

Bitter's episode notes list the rest of the setup. Polarized training (mostly easy running with a few protected hard sessions), very long long runs, VO2, 10K and 5K work carried through the marathon block, and a public Strava profile that shows all of it. Nobbs went from a 2:19 debut to 2:09, and Bitter says he is targeting a two to three minute PR at Chicago in a couple of months.

Bitter followed up with why he thinks the profile is worth reading.

What the amateurs are doing

The same week, kofuzi posted a Berlin build long run where he alternated regular carb and high carb bottles over four laps and finished with 268 grams of carbs in two hours and 26 minutes, a personal high. He says his stomach was gurgling about an hour and five minutes in, at 139 grams, but he called it one of his best long runs in a long time.

At the other end, a r/Marathon_Training poster ran a 2:57 marathon debut on about 50 grams of carbs an hour, blew up at mile 21 after going through halfway in 1:22:30 in heat and humidity, and wrote that he had heard the body can only absorb 60 grams an hour, so he is not sure how more would even work.

The myths still doing the rounds

Believe in the Run's Fuel for the Sole hosts spent episode 140 knocking down carb load advice. Doing three days of keto before a carb load comes from 1960s research that is now debunked, they say, and the claim that you should skip bread and eat only potatoes and rice has no scientific basis. They also told a listener chasing sub 3 at Berlin on 60 to 90 grams an hour to bring their own electrolytes, since the course has frequent water stops and Maurten drink mix but no electrolyte.

Nobbs's number is one athlete's self-report, not a study, and nobody is telling a 2:57 runner to jump to 120 grams. The gap between what pros are taking and what most amateurs believe is possible is the fueling argument of this marathon season, and Nobbs is unusual mainly in publishing his numbers.

Zach Bitter

@zbitter

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He doesn’t just run slow all the time and as a result plateau early, but rather runs much slower than he could most of the time, so when it is time for quality work, strides, and races he can rip.