Yes, very willful, but I found the longer I went without eating the less willpower it took to continue.
It would kill me to try such a thing these days, but if you are in good physical health and hopefully have some extra fat for your body to deplete, I don't see why it can't be done. David Blaine is no doubt in good shape as well as very willful, and his hunger strike for 45 days is 50% longer than I went, but by no means is it 'magic'. What it is, is being callously brutal to your physical body through a test of your will power.
I think the stunt where he stood on top of a pole would have been more difficult. I think my back would have screamed so loudly that the people on the ground would have heard it!