Why do you lose your breasts first when you lose weight?

Answer 1

This is just an educated guess, but I'm betting that you lose the same percentage (say, 10%) of fat everywhere in your body when you lose weight. In a place where you have little fat and lots of muscle, 10% of fat loss wouldn't be very obvious. Because your breasts are mostly fat, 10% of fat loss would be much more obvious, making it seem like you're losing more weight/losing weight first in your breasts.