This seems like a dumb question but I have this nightmare I'm going to lose the weight but the moobs stay the same size, making them impossible to hide. Moobs will shrink with weight loss, right? Otherwise I'm half willing to stay fat (even though fat itself sucks.)
they'll most likely deflate - how much will depend on how naturally endowed you are to begin with; and even then they'll still be smaller over all.
losing weight makes binding soooo much easier, regardless
also - losing weight will make top surgery results a ton better, if that is something you plan on doing eventually.
I've lost fifty pounds (about 22.7 kilos) and my chest has shrunk quite a bit. There is still the glandular tissues, but over all I went from a very large B cup to barely filling up an A cup. There are obvious bonuses of being overall healthier and feeling better about myself as far as losing weight is considered. In some cases I pass less than I used to, but the overall trade off has been worth it. Also, with fat redistribution, despite the fact that I naturally have Marilyn Monroe's figure, my curves are much less noticeable even with being fifty pounds lighter.
If you're comprised of a lot more fatty tissue than is necessary, then losing weight is never a bad idea. It might also get rid of some excess fat in your chest that wouldn't be there if you weighed less.
Even if I don't get too much loss from my chest, I know that if I can get a bit thinner, binding will be overall more comfortable- too much belly for that double front :P So that alone would be worth it, at least for me.
Though I haven't heard of a single case where they stayed the same after weight loss :)
I'm not 100% sure what's at fault here but a combination of being on T and losing weight has made my chest next to nothing (at least when compared to my gut). I had one friend tell me that I could probably walk around not binding with just a T-shirt because my chest looks like that of a chubby guy.
I think it could depend on how much weight you loose, and what your size would be at your proper BMI, and probably a ton of other factors. I used to do track in high school, and while I didn't loose any cup size despite getting in better shape, my gf (who was thin and healthy to begin with from doing dance) went from a D to a C, and some other girls went down about 2 cup sizes.
I don't know my cup size, but in the past year or so I lost about 5 inches off the fullest part of the moobs. Granted, I also lost 5 inches off my chest under them, so I believe that makes the cup size stay the same, but to me they still look and feel a lot smaller and they definitely bind better.
They're mostly made of fat, so if you lose a good amount of fat, you're most likely going to lose from there along with the other places-- but like others have said, it depends how much fat you have on them to begin with. People are genetically disposed to carry their fat in different places and generally you'll lose it first where you gained it last and those places it accumulates first will be the slowest to give it up (for me it seems to be my thighs... blech) . Our genetics choose where that is-- we don't have control over it (so you can't "spot reduce" like some people claim). So if you already have a good amount of fat on them and aren't genetically disposed to hold on to the fat there for dear life, if you lose fat all over, you'll most likely lose at least a little there.