They just don't want to believe that is possible :)  I still roll my eyes at my skinny older sister — and all the other girls who were born with fast metabolisms and choose salads over hamburgers —but I'd much rather be the girl that can appreciate a good meal than the hangry girl bitching out the barista in Starbucks, living off of their non-fat, skinny mocha lattes and counting down the minutes until her next cheese cube.  This dichotomy always makes me laugh. I am skinny, yet I love food and I am never 'hangry'. I believed the 'fast metabolism' garbage until I actually started tracking my food intake a year ago and found that I was regularly undereating. I wasn't 'blessed' with a high metabolism, I just didn't stuff my face at every opportunity.