Fatshits in my office are constantly asking me "How do you stay so skinny/thin?"    I used to explain it to them very simply.  "Eat Less & Exercise More."    Every single time I would say this I would watch their eyes glaze over & they would never ask me to elaborate... until a few years later when the same person would again ask me how I stay so thin.  (Because fats are stupid).    Now I no longer bother to educate them, I actually just shrug as if I have no idea, or I'll say "Well I COULD tell you, but what's the point?" (I actually really like this one as they sort of can't really tell if I'm being insulting or not).