I've been wearing mine since August, and I've already noticed that my chest is much flatter than it was when I first began binding. However, I have also noticed that some days, my chest is flatter while binding than others. If you keep estrogen-inducing foods out of your diet (for the most part), you might be able to get flat with a sports bra. I saw something in the section a while ago about how milk produces estrogen, which makes your breasts appear more "plump", I guess? So I try not to drink too much milk.