I'd have to ask how you are losing weight. If you are trading off fat for lean body mass your energy level should increase. However, if you are not excercising and building muscle but rather focusing...
How much you can lose depends on how much you have to lose. Weight watchers use charts for allowable weights vs lengths vs serving sizes, so if you follow the guidelines there's a limit for how thing...
Oddly not too much (at first anyway). Your body goes into starvation mode and conserves energy anyway that it can. When you do eat again, the body will pack most of that away as fat because it...