Pardon me for saying but this thread has seemed to have become a particularly mean and hostile place in the past week or so.
Lets just assume this thin person has an eating disorder.
And he may not, he may just be a thirteen year old kid. From his picture, it wouldn't surprise me one bit.
And lets take it off the table whether minors should be in the forum for the moment.
Bullying him into compliance isn't the answer- either way.
I posted pictures for my part, didn't even get a response- and perhaps I dodged a bullet considering how others have been treated.