Is it true?

Is it true that if you breastfed your breasts are just "gone" ? I've heard that from a lot of people. My cousin used to have double d's and now they're so much smaller. She said it was because she breastfed.. when im ready to have a child in the future I want to be able to nurture my babies naturally without that disadvantage. But no matter what I hear I will do it anyway. Was this true for you?