Will i lose weight by doing this?

Hi I'm fifteen and a little bit chubby, i'm probably around 12 stone (bare in mind i have big bones). I recently decided to cut out all junk foo (which I used to eat a lot of) and I've started eating more fruit. I've also cut down to one meal a day, with the occasional snake of a muller yogurt. For the time being I can't exercise because i'm studying for my junior cert but i will be able to start going in the summer. I'm just wondering right now will I lose much weight?