How long can I go without eating before something serious happens?

Ive been sick for 9 days and I havent held down any food for 3 and a half days now. Doctors told me I just have a cold and sent me home with an inhaler. I have a pretty good fat reserve I guess, I got a decent beer gut.. like nothing huge but I'm husky. I've also been taking vitamins and whatever I do eat seems to get partially digested.. but thats it.