Zach Bitter's 100-mile World Record

Unless you were lost at Burning Man for a whole week, you would have heard that Zach Bitter set a new world record for the 100-mile run in 11:19:13, crushing the previous record by almost 10 minutes. He went on to break his own world record for the 12-hour run by running 104.8 miles in that time frame. Perhaps the most impressive (other than that whole world record blah blah) was that he ran negative splits, which meant that his second 50 miles was faster than his first.


I first met Zach at Low Carb USA 2018 in San Diego, and you can guess where this is going (it’s not because he’s a typical sugar-addicted endurance athlete out trolling low-carbers at conferences). Among the kudos and adulation for his WR run, there was nary a peep on his diet which is, of course, one of my primary focuses.

If anyone wanted to know - and it’s probably the worst-kept secret in the world - Zach trains low carb and has been mostly carnivore in the last year or so. His macros average out to be about 10% carbs overall, which varies based on his training volume. Zach co-hosts the Human Performance Outliers podcast and has recorded over 150 episodes with carnivore promoter Dr. Shawn Baker, of which he has interviewed pretty much all the big names in the field. There’s a lot of focus on not just the diet, but of athletes who perform at extremely high levels, doctors who remedied a host of illnesses using low-carb diets, and scientists studying how grazing ruminants can improve land use and fight climate change.

After having followed Zach since even before we met (coming off my first and painful marathon in July 2018), I significantly improved my body of knowledge on how athletes should fuel. It isn’t because low carb athletes always perform better or that burning fat generates more ATP than burning carbs (neither of which are true). Rather, it is because fat metabolism lowers inflammation and therefore the risk of injury. Zach said more than once that he had been blessed with only one significant injury in his running career that prevented him from training and I echo pretty much the same. I get sore but rarely hurt myself, and recovery never takes longer than two or three days even after a major race.

I weigh 20+ lbs more than Zach, so this is clearly a power/weight ratio issue.

I weigh 20+ lbs more than Zach, so this is clearly a power/weight ratio issue.

The physiology behind this makes simple yet perfect sense. Exercise can reduce stress in the long run, but actual exercise tears down the body and induces acute inflammation (which is a normal process of how the body repairs itself). Fueling with sugar raises the base level of inflammation which is chronic, and this prolongs the recovery cycle. The longer the runs, the more sugar one consumes (the run clubs are particularly guilty of this as they are full of young people going out and blowing up the bar/buffet after a 3-mile run), and runners are taught to frequently fuel with sugar. Thus, they never develop the ability to metabolize fat well and are reliant on sugar, and sooner or later this worsens insulin resistance. Some develop diabetes.

The one other thought about this is that I don’t think Zach was an accident, nor do I believe he is a prodigy. He had been consistently working toward the 100-mile goal for 6 years and all of his training, diet included, contributed to that. He mentioned more than once that someone better-situated could probably come in and break the 11-hour record. It was disappointing how little the press mentioned his diet or the podcasts he hosts (virtually no coverage in either the Runner’s World article linked above, or the Washington Post), but as any semi-serious endurance athlete knows or should know, having the ability to train injury-free could make all the difference between you and your competitors.

Follow Zach Bitter on:
Twitter @zbitter
YouTube @ZachBitterUltra
Instagram @zachbitter