Some people are just blessed with high metabolisms (downside though is one guy I met would almost pass out suddenly when he got hungry because he burned through it all..kind of scary).
I get a bit frustrated too with people who say they're on a diet then eat all sorts of junk food and take out then complain about not losing any weight. Or the ones that insist they need the junk food then blame everyone else for bad foods.
I do get really depressed by the skinny girls who say they're fat but when I'm in a patient mood I'm able to remind myself that we've all got our own body issues...it's just frustrating when you're sitting next to a girl that literally wears a size 0 and she says she "sooooo fat, such a whale" because it makes me feel like wow...if you're a whale then I'm apparently the size of a planet
Hmm, this may sound random but I've actually had a few guy friends get after me for NOT eating because my body gets stuck in starvation mode so I can't lose weight.