It's the circular ham-logic. "I eat 500 calories a day and still manage to maintain a regular 5lb-per-week weight gain.  It's obviously not calories, it's [insert excuse]."  "That bitch is so skinny!  Hey someone tell that skinny whore to eat a hamburger so men will want to fuck her!!  I'm so empowered."  "Fuck society.  I'm a fat cunt and if I want to eat a dozen cupcakes at once then no one can stop me.  I love my fupa."  "Ugh, my genetics make me gain weight by just looking at candy.  I haven't eaten over 500 calories a day in months." etc, etc.