The only theories I've seen so far is that the magnetic flux effects the iron in the blood, or that it ionises the glands causing growth.
But iron does not remain magnetised like steel does, so for the first to be true, you'd have to do it 24/7.
You could possibly (but probably not) create eddy currents in the iron with the magnets, but its really not going to be a strong current, and if it worked then you might as well just try some form of electro shock therapy instead.
And then the ionisation theory, you don't want to ionise cells, ionising cells is why people get cancer after exposure to nuclear radiation.
If your breasts swelled from ionisation, you'd need a mastectomy.
Started properly October 2014 - 34A
Goal - 34C/D, which is probably not realistic, but I can dream.
magnets do not ionize anything, all the way down to the atomic level. in order to ionize something, you need to remove or add a single electron from an atom. a magnet neither adds or removes any electrons from any atom. the best they can do is allign the atoms following the magnetic feild until the field is moved away, then they re-allign in random directions as they do normally. basically, any claim that a magnet "ionizes" anything is a complete scam. at best, its placebo and/or self hypnosis, which i have far more faith in than claims of magnetic ionization