That's why a proper dietician-supplied diet will go for a calorie deficiency of a few hundred, max 500 below your maintenance; any lower and your body will go into hunger mode, and simply use less calories. Eat less, but not too much less. Losing a pound per week is about the maximum you should aim for. It'd probably be more if you're obese, but along with the fat you're losing a lot of water. (also, carbs cause more water retention)