This gives them the opportunity to get used to your nipples, while giving you time to establish a good supply of milk. (mymilkybaby.com)
This will not only help you lose weight, but it will contribute to a better supply of milk for your baby. (howtoadult.com)
This isn't necessarily related to the size of your breasts though, as some women with smaller breasts may have a good supply of milk - making glands, where a mother with larger breasts may have more fatty tissue. (pinkymckay.com)