At a glance
WHAT IT’S REALLY ABOUT
Ultrarunner Zach Bitter Explains Fat-Fueled 100-Mile World-Record Performance
- Joe Rogan interviews elite ultramarathoner Zach Bitter, focusing on his transition to high-fat, low-carb nutrition while running and winning extreme-distance races. Bitter describes how he became hooked on ultras, culminating in a 100-mile American record of 11 hours 40 minutes on a track, averaging about seven minutes per mile. They dive deeply into metabolic flexibility, fat adaptation, carbohydrate timing, and how he uses nutrition to avoid bonking and stomach issues over 100+ miles. The conversation also covers training structure, mental toughness, gear, the culture of ultrarunning, and how different bodies thrive on very different diets.
IDEAS WORTH REMEMBERING
5 ideasFat adaptation can dramatically reduce fueling needs during ultras.
By becoming highly fat-adapted, Bitter can run 4–5 hours on just water and electrolytes, and in races he typically only needs 100–200 calories per hour, about half of what he used on a high-carb approach, which lowers the risk of stomach problems.
Metabolic flexibility beats strict ketosis for high-performance training.
Bitter uses very low-carb/keto phases to build fat-burning capacity, then strategically adds back carbohydrates (often 200–300 g/day in peak weeks) to replenish glycogen so he can still hit high-intensity workouts and race efforts.
Recovery time between sessions may dictate carb needs more than workout intensity alone.
He suspects athletes training once per day can stay very low-carb, but when he stacks two-a-days with speed work, he needs more fast-acting carbs to restore glycogen quickly enough between efforts.
During races, carbohydrate is the smart supplement to body fat, not dietary fat.
Since even lean runners have ample body fat to fuel the ‘fat-burning side’ of the effort, Bitter opts to sip carbohydrate drinks during events to top up small glycogen stores rather than ingesting additional fats, which are already abundantly available from his body.
Mental strategy and logistics are as crucial as fitness in ultrarunning.
Bitter emphasizes pacing by perceived effort, planning aid, hydration, and gear, and using smaller races as “moderately hard long runs” to rehearse race-morning routines and logistics without blowing his peak performance on a B race.
WORDS WORTH SAVING
5 quotesIn 100 miles it’s almost not a matter of if something is going to go wrong, it’s a matter of when and how you respond to it.
— Zach Bitter
If I can go for a four- or even five-hour run with no fuel other than water and electrolytes, then I’m fat-adapted enough.
— Zach Bitter
Even the leanest endurance athletes have enough body fat to get through an endurance race.
— Zach Bitter
There’s something about the mind of an ultramarathoner. The type of person that can run 100 miles, 200 miles… those type of people, they’re different people.
— Joe Rogan
I’m not trying to say everyone should switch to doing what I do. If you feel great, do what you’re doing. If you don’t, then probably look to change something.
— Zach Bitter
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