Boobs are mostly fat...lose the fat, lose the boobs. Period. And the skin, well, that doesn't really get any smaller so what used to be big boobs can start looking like cow tongues. But like Maniac said, building the pec muscles does help to give the illusion of fuller breasts, as the muscle beneath helps to make them push out, so to speak. It's unfortunate for girls who do work so very hard to look so incredibly fit, that to remain looking female they feel forced into breast augmentation. I applaud those that don't feel the need to get a boob job. I myself, would love one.