I think most guys on T that report losing weight do so because they are more comfortable in their skin, happier to work on their body (because there's finally an end goal to their means—a masculine figure), and often get out more once they feel like they're passing and such. T probably won't help you lose weight without effort, same as without T. When I lost weight (I'm now 32 lbs lighter than I was in November) my chest shrank significantly, I went down 3 inches or so on my waist, and I just generally started feeling better about everything, trans-related or not. At my highest I sat at about a (tight) 38D at around 183 lbs, 36-38 waist, and I am only 5'4. When I went into my consultation for top I was measured at around a 36C, I believe. I'm not too bummed the number didn't go down much, as I'm barrel-chested like my father, but yes usually weight loss will drop your chest size significantly, depending on how much you lose. Weird they won't do surgery if you're too hefty, it's totally not like that in the states, as far as I'm aware (to a point).