Beer is not only caloric, but contains alcohol. When alcohol is ingested, the body's fat metabolism practically stops until it's out of your system. Drinking a beer each day would almost make it impossible to lose fat efficiently.
It wouldn't matter if you were eating under, because your body would not be able to easily burn fat for fuel. Instead, it would burn other things, acetate (from the alcohol), carbs, your own muscle, then fat, etc.