You don't lose fat cells, you only reduce the size of them, and it can take weeks or months after burning fat for the cell to shrink to it's new size. Evidently, water frequently moves in to replace the volume of fat lost and you have to outwait it. BUT - keep exercising, and when the cells do resize, you will see the definition you've worked so hard to achieve. Resistance training is great for this, as is a five minute ab routine three times a week. Keep at it, you're worth it.