As a teen, how can losing weight make the size of my boobs change?

Loss of significant amount of weight at any age can make the breast lose volume and increase skin laxity. This can lead to "involutional atrophy" or loss of volume and decreased upper pole fullness of the breast. Patients over the age of 18 may be good candidates for breast augmentation to enhance size, shape, lift, and volume. Significant weight loss may cause severe skin laxity requiring a Mastopexy or breast lift as well.