Monkey, it depends on a lot of things, how much you eat, how quick you metabolise foods, what other activities other than running you do and probably a whole host of other things.
I don't think you can really give exact figures. But to give you my own experience, I train for at least an hour every day, 2-2.5 hours on a sunday (if I don't have a race), and one day off in a week. My sessions vary in effort and intensitiy.
Through running (this is the only activity I do now) I have lost three stones since I took up running last year. I was 20% body fat when I started and I am now at 10.5%.
If you are just starting out, then you have to start small, overdoing it will only lead to injury and illness. Start gradually and build up mileage; the golden rule being never add more than 10% of the previous weeks mileage to the current week.
You may find you are getting more hungry as you build mileage, this is fine, as I also eat more now than I did when I was three stones heavier. Although now, like yourself, I eat well.
Good luck with it, let us know how you get on.