Ultrarunner of the year for 2018 will possibly will go to Jeff Browning, low-carb, low-key, smart AF and fully fat-adapted.
Arguing what running star eats what is a waste of time.
So why tell us about Jeff Browning?
He does eat carbs, btw, just not as much as most. And he sucks down loads of sugar gels during races.
He's great and deserves ultrarunner of the year. I've listened to him on several podcasts and I like him, but he does have a tendency toward getting into faddish woo.
I tell you about Jeff Browning because he is low-key the smartest and most consistent ultra guy out there, and an example for all runners of how to be persistent in trouble-shooting your own limiting factors. It has allowed him to be one of the best when most have waved the white flag (mid-forties). This is where he separates himself from guys like Sage or even Walmsley. As a result of his evolution , he now qualifies as low-carb by any standards of a running diet (although on back-loading days he may approach 200+g, as does Bitter).
As far as carbs in-race, ALL ultrarunners must do this to be competitive, even keto-adapted athletes. In-race carbs for keto athletes are more like a rocket boost than the dire necessity they are for sugar-burners. The difference is that guys like Zach and Jeff are consuming 60-80% less carbs than guys like Walmsley or Sage (see Volek's brilliant FASTER study for the physiology of why). The result is more long-term efficiency, and fewer gastrointestinal issues (hi Sage!).
The issue isn't carbs v. no carbs, it's excessive carbs v. smart carbs. Jeff has it figured out. Although I don't have his talent by any stretch, his journey from high-carb vegan with constant body comp and GI issues to low-carb ketoadaptation and greater health and performance mirrors mine almost exactly (listen to the podcast for details). I am not an ultrarunner, but I have more than doubled the distance on my long runs (12 to 30 miles) that I can do without any caloric intake whatsoever, and with no bonking or drop in pace or energy. This is just a bonus for me, since my competitive events typically only last 1-5 minutes, 30 minutes at the outside.