do a search, it has been debated endlessly in this forum.
basically some say all you will lose is muscle if you don't decrease all the cortisol floating around in your blood with some food first thing in the morning.
Others swear by it and say that is the only way to lose stubborn fat because of lack of substrate in the morning your body is forced to burn your stored energy (aka bodyfat).
Only way is to try and see how you specifically respond. As i said do a search for a more detailed answer.