> Combining this with the fact that Everest climbers are apparently eating 10K+ calories a day and then up to around 20K on summit day, I have to wonder how these facts jive...if they can really temporarily push the limit, for how long, etc.

Yeah, I'm not convinced the article passes the smell test.

Michael Phelps discussed his diet extensively, suggesting he ate 10k a day while training. Other athletes talk about similar meal sizes. This suggests that once they stop exercising (thus eventually losing lean muscle mass and requiring less calories) that they would not see a change in their weight, yet there are a lot of old fat athletes (possibly just of a certain generation) out there.