Please help, i want to lose weight real bad?

Im a 17 year old girl, and i really wanna lose weight in my two months i have off from school. Im really interested in doing the 2 month insanity program, im outta shape but im willing to work out hard. I was wondering how much weight one can lose on this program and also is it true that inches come off faster than pounds? I also want to if u guys recommend any supplements for me while on this program. Please lemme kno! Thanks