This is an old bar trick, but I have never heard of it with only one piece
of bread - usually the amount is 3 or 4 pieces. Moreover, it works with
just about any bread. It can be done, but out of the 20 times I have seen
people try (and there was alcohol involved) only 2 could actually eat three
pieces in 60 seconds.

Try it for yourself. Buy a loaf of bread.