protein shakes??
from my experience, the answer to your question, is yes. If you consume less calories than you burn, you'll lose weight. That's just plain biology and math. And if those calories are primarily protein, it'll be that much better.
I think that if you try it for maybe 3 days, you should be able to see the numbers drop, then you'll have a better idea of how your body will do it.
Also, you might want to take a good look and make sure you haven't added any empty calories to your diet. If you've upped the carb or sugar intake, then eliminating those things alone may help a great deal.
good luck!!