If I stop eating the way I do, will I lose weight?

I'm 16 and female, I'm 5, 11" and weigh about 10 and a half stone. Which I feel lucky! I have a might metabolism at the moment but am worried about the consiquenses when it dies down. I eat about four packs of crisps, two chocolate bars, 2 litres of coke, cake, ice cream, chips every day. And I have a large mc donalds, dominos, curry and burger take away EACH week. If I cut this out, will it not only help my decreasing metabolism but help me loose weight too?