I'm not a teenager (!), but to answer your question: about a year ago, I did Tae Bo for a whole year. Can't remember how much I lost, but it did make me stronger! Not only that, by doing it reg. (@ least 20min. a day), I felt more focused (I have ADD), & more confident! Try it! I'm trying to get back into shape, too....I recommend Tae Bo Basic, &/or CRUNCH/Tae Boxing. Also try a Pilates Video....