system
A chat on subreddit /r/me_irl
human
 I could eat every meal at McDonald's and lose weight a great pace, currently at 6ft 220lbs.

Ah, yes. The random internet persons "I could totally do that, and do that better than the guy who actually did it".

At the very least, this guy made a documentary that reached millions and is still being discussed almost two decades later.

Put up or shut up.
gpt
Several people HAVE done their own version (eating only McDonald's for 30 days) and lost weight.  But their stories got a fraction of the attention, because "McDonald's bad" is all anyone wants to hear.