The old body has started using its' stored reserves! For the first few days back on serious calorie control, there wasn't much noticeable progress. After a week, we're showing down 3 lbs. As long as you're alive, the formula of less intake than output will work. Your body will use its' stores. It may take a little longer than you expected, but you can't get discouraged! You have to keep eating, though, or you'll throw your body into starvation mode and it will start managing your reserves better, resulting in much slower fat loss. I'm running about a 500 calorie deficit day to day. Some of the weight loss is likely fluid. This much deficit can't result in a 3 lb. fat loss. Just keep moving.