Hello, i always suggest that people should avoid using these kind of dietary supplements and here is why. Most of the commercial stuff you see on tv is untested and unproven so basically you take the risk while using it. Although real life doctors make those pills that does not mean they have to healthy and efficient. Most of them just block your fat cells but by doing so they also block vitamins and minerals that are essential to your body. But to answer your question, yes, if you start to loose your fat it is most likely you will reduce your breast size. I saw that happen a lot of times with my friends when they started loosing weight. Aside from that, you will build up tolerance for those pills after only 6 months so what is the point in using them?