I don't know... It amazes me too! A couple of years ago, my mum screamer when she seen my ribs sticking out of my chest and I decided to get myself checked out. I told the nurse I an concerned because I am underweight, loosing energy quickly and I don't think seeing my own heart beating is normal. So, I got all my tests done, expecting something to solve my answer, days of waiting... Only to be told, 'I didn't know if you knew this, but you are marked as being very underweight'. I am sort of aware of that one, Sherlock... That was an awkward couple of minutes of answers that are still unsolved.