"...But that can't just be with. What specific have you done?"  At work I used to get asked that, still do by some of the same people. I have just given in and told them what they wanted to hear, "I've been starving myself for the whole week just so I could eat today." After going out to eat with the guys, "Food coma, I think it's time to purge." When they say, "You better watch what you eat or you'll look like me." My favorite come back is, "I'll be fine. Liposuction runs in my family."