Not true ... the real reason guys get moobs is if they drink a lot of tap water or anything that comes from tap water. When a woman pees or anything and flushes the toilets, they release Estrogen into the sewers. This is then transferred to a purifying plant where the water is separated from the human waste, rubbish, etc. leaving plain water that is then used in taps and places as drinking water. Problem is that Estrogen (the female hormone version of Testosterone) can't get taken out with the rest of the stuff and is left in the water. The resulting estrogen-rich water can biologically nudge our bodies into certain directions (ie getting moobs) if enough is built up over a long time.
Incidentally, in some places where they just wash sewage out to sea instead of recycling it, various types of fish are well known to switch gender.