A coworker of mine called me on my 'issue' a while back.
One afternoon, I was going up and she was going down the stairway and we got to chatting a bit. Nothing major, just general pleasantries. All of a sudden, she took my hands in hers, started examining the fingers/nails and said quite decisively, "you're bulimic, aren't you."
Flustered, I blurted out, "why'd you say that?"
She blushed, apologized, then said that she was, and that she noticed the ridges and spots on my fingernails. (I used to paint my nails to hide it but gardening, typing and piano-playing rendered maintenance too high.) She showed me her nails (almost totally bitten down, but spotty) and said that it was a constant struggle for her. Also told me that she'd had to have all her teeth capped, too, because of this.