if anything if your bra size is a 36 it might change to a 34. if your breast shrink from weight loss it maybe a little reduction.
i've gained weight and the inches and my breast cup increased. i was also taking a birth control pill that states that it can cause an increase in breast size.
Your breasts are made up from fatty tissue. Weight loss (burning fat) can thus affect your breasts but not in any great way. Your breasts are supported by muscles over your breast bone. Exercising these can give you a better posture and lift the breasts a little bit. It is however still the same breasts.
The easiest way to look and feel better about your breast size and shape is to get a bra that fits properly. Many many woman wear the wrong size bras so it is important to get yourself measured properly in a good lingerie store and wear clothes that flatter your figure.
i agree with susan, some bra's are cone shapped, that looks like bullets ready to go.
some are padded push up bras
some are under wire bras-which is the only kind i like.
some bras dont have the under wire.
for some big breasted women they have a criss cross support.
some bras are so thin it allows your nipples to show throuh