I might ever heard foodie, but I'm not really sure what it really means or how to use it. If you are specialized in food, like all kinds of activity involving food? I'd say you're a Food Master, or a Foodman, or probably a Food Hero.
Referring to the word Junkie, it probably came from Junk. In my country, Junkie means a person whose attitude and appearence is close to Junk. Therefore if you say someone is Foodie, then it prolly means that the person smells like food and he could have some sort of ability to draw people's hunger once looking at him?