If you assume I'm diabetic, I can assume you're anorexic.
Seriously, what right do you have to assume my health just by the way I look? If you assume that because I'm a little overweight, that must mean I have "the diabetes!", I can assume that because you're skinny, that you're "anorexic".
Why would you believe that someone can eat all they want and still be skinny, but if a fat person states that they work out and eat healthy regularly, it's somehow impossible? That's hypocritical.
Not all bodies are created equal, and life is hard enough without size prejudice.