I've burnt over 1000kcal in an hour cycling and I'm over 50 and not super-fit. A few hills can make all the difference as it's difficult to be lazy whilst grinding your way up-hill.
1000kcal in an hour is around 277 Watts for an hour. There are very few people who can sustain that without serious dedication and long hours for months/years.
1000 kcal per hour is 278w FTP if using common convention of 1 cal = 1 j of work (assuming ~20% COP). A lot of people who are very fit dream of such an FTP.
Well, looking at average ranges, 278w FTP would put me in the top 40% or so, which I would consider is reasonably average. Also, I'm reasonably heavy (around 100kg), so that probably makes it easier to put out some power whilst also meaning that I'm slow up the hills.
That's a) self-reported and b) among cyclists who track their power i.e. have power-meter equipped bicycle and a head unit to record stats. Self-reporting inflate the numbers by itself but, since most people don't actually have a power meter or/and don't bike, that group is made from quite fit people by selection.
