I had breast reduction surgery in my early 20s. It changed my life, but it was incredibly painful and recovery took a long time.
But, as others have pointed out, they tend to grow back. I am now the same size as before I had it done. And no, it isn't weight gain, because I am no bigger overall than I was when I had surgery, in fact I might even be slimmer.
I am still happy I had it done, but the reality is that when I had it done I simply couldn't get bras to fit. Not that I couldn't get comfortable, or pretty bras, but I couldn't get any. And I was battling utter self loathing due to attitudes like that expressed upthread that only overweight women have large boobs. As a teenager I truly believed that I was the only female in existence who was slim but with big boobs, that I was a freak, disgusting, repulsive etc, because I was bombarded with ill informed teenage, and then women's, magazines writing articles about buying a bra and declaring that anyone wearing a C cup was huge.
Now, the situation has improved so much. There is a huge range of bras available in large cup sizes. And they are pretty, in a variety of colours and styles. And the very fact that there is a huge high street chain dedicated to such bras means that any teenager now in my former situation can see clearly that they are not a freak and hot even particularly unusual - high street chains don't thrive without customers.
So, now I am the same size as before and whilst I'd love to be smaller, I really don't give two hoots overall. I'm not in pain this time, because I can get bras to fit, and I have nice underwear. And best of all, at my age I am confident enough to tell anyone that makes snidey comments about it being impossible to have big boobs when you are slim that they are very much mistaken and they should educate themselves. Which they should.