I've been going to the gym for 2 years now with a personal trainer - mostly a wholesome approach and even when doing HIIT intervals, I'm not getting even close to my max of 194 I've seen before starting going to the gym when I tried to climb the tiny hill close to my house on my bike.
His experience seems anecdotal at best and an extreme case of cherry picking alongside that. I do feel some nausea after a decent workout usually and it does suppress my appetite for a few hours, but I know of people that are just ravenous after working out.