will wegain weight after leaving aerobics

First of all why are you thinking in such a negative way? If you start with aerobics you will see how great it is. And when you start to exercise you will discover that you feel better not just physically but also psychologically. Ok, it is going to be hard at the beginning and there are going to be some sore muscles but after just one month you will feel the difference. You are going to smile more and you will have more energy and these are just few benefits of aerobics and exercising in essence. And you think that you will stop with aerobics and regain weight? Answer to this is no, no. Maybe you will take a break after some time but just be sure that is just a short brake (a month is acceptable). In that period you will realize that you miss that good feeling that only exercising can give you so once you start there is no way you are going to give up that easily. Let me know about the results.