by Eliza Barcla January 28, 2011 NPR   Bacon is cut from the pig's belly, and is one- to two-thirds fat.     Recently, an old friend who's been a vegetarian for more than 15 years shocked us with a story: Last weekend, she ate bacon. Several strips. Straight out of the frying pan where her boyfriend was cooking it.   This wasn't the first time she'd encountered it sizzling there, in all its…