It's probably mostly water weight and alcohol bloating that you lost. I had the same thing happen. Will happen the first week too on a regular diet like Weight Watchers.
So that's probably about six pounds of it, and the other two are the thousands of calories you are NOT consuming of alcohol. After a while the body gets used to getting its calories for booze. You might think you are eating a lot, but I bet if you actually count calories you will find you are ingesting less than the maintenance 2000/day and will still keep losing weight, just more slowly.