My girlfriends sister, who is 17, used it on her legs and the back of her arms. She said that it made a big difference for her because she was having a huge amount of trouble losing that fat. She was not fat before, but I must admit that losing the fat on her arms made her, on the whole, look a lot thinner.. even though she really lost only a little actual wieght.
I dont really know if there is an age limit, though think that most supplements reccomend 18 for legal reasons. I would say that by 16 most girls are more developed than their male counterparts at 18. I also know that telling someone that is 16 that time will change their body is not the answer. Because when you are 16 its hard not to be concerned about appearance NOW, since it seems like everyone else is.
But I also, in agreement with liftsiron, think that a good lifting and cardio program are essential but that goes for everyone.