Would fat make breasts bigger?

Yes: Since breasts are largely composed of fat, then any increase in fat would certainly make them bigger.

Yes, Breast size is : Likely to ^ w puberty, pregnancy, breast feeding ; possibly prior to your period. You can build up chest muscles w exercise ; weight lifting but it will not ^ the amt. Of fatty tissue. There are no pills, herbs or machines that will ^ breast size. Breast augmentation is surgical enlargement. A padded bra will ^ appearance of volume. A supportive, well fitting bra can also enhance appearance.