I think it can definately start in childhood. And I think if it does it's a much more difficult habbit to break because it's so ingrained. The problem with choosing food as your 'drug' of choice is that it's the only 'drug' we have to have. We can't live without food, but we can live without, say, alcohol. So someone can kick the habbit of alcohol cold turkey and not have any near them, but with food we have to eat to live so that's why it's so much more difficult.
My addiction started when I was young and left alone alot at home when my parents worked. I used to come home to an empty house and eat to do something, keep myself busy, try to stave off the lonliness. I do it all now. I can recognise it better nwo, but it makes it no easier to stop doing it at the moment.