Hey dude, I'm new here aswell I weighed around the same weight as you when I was 15 although It wasn't down to over eating. Rather i was consuming around 2 litres of Coke a day =\ anyway if you got msn then add me if you ever need to talk or anything.
P.s Gratz for starting to do somthing now I started at 14/15 and failed now I'am going to have to do it into college and late teens get yourself fit and confident because the older you become the harder it gets m8.
-jack