Endurance athletes know that you have to eat to compete. But ultrarunner David Roche has taken that maxim to the very edge of science, choking down carbs and ketones on his way to setting a course record in the punishing Leadville 100 trail running race. Your mileage (and digestion) may vary, of course—and so Spencer Campbell put his own body on the line to play guinea pig.

As I felt my pace quicken almost effortlessly, I wondered: Was Roche’s prescription finally working? I repledged my allegiance. I bought two cases of Precision Fuel gels because he used them. I chugged 24 ounces of water before each run to acclimate my stomach to all the gel and liquids I’d need to down during the race, just like he did. (Roche copied techniques perfected by competitive eaters.) I visited three different stores to find ketones.

I also got tougher. I completed my longest prerace run, 17 miles, on the last day of May. I posted my fastest paces during the final three miles. Even more astonishingly, I started to welcome the punishment of the path.

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