As a thin person I hear it all the time. Never mind that I watch what I eat and work out 6 days a week. Somehow I am privileged. It never occurs to them they could do same.

I assure you it is.

Oh it's a thing!

Thin people absolutely get treated better than heavier people, in countries where being thin is the standard for attractiveness.

It is, although I’ve never heard it called that. Anything that translates into “beauty”(and in western and Asian countries thinness does), is an advantage in several situations—and not just social ones.

Yes this absolutely exists. Same as men who are well built and are incredibly muscular