I want to make my friend realize something without being mean?

Okay, so im pretty thin and conseqeuntly flat chested and i accept theres not alot i can do about that (not really into pushup bras). Anyway my friend makes fun of me for it, and i just sort of play it down and act like i dont care. However, its starting to get annoying. Shes well-endowed, but she's also overweight. If she didnt weight as much as she did and sit on the couch and eat crap all day she might look alot more like me. I want to point out, as politely as possible, that she shouldnt really be making fun of me for having decent eating habits/exercise routine. I hope im not coming off as a jerk here haha shes my best friend and i luv her, iim just getting tired of the teasing. I dont want to tell her to just stop because i dont want her to know im really sensitive about it. Any advice?