Congratulations on your great weight loss! It's terrific to get such a boost after the first week, isn't it? Makes it all worthwhile.
After the first week on a new diet the weight loss can be quite big, this is because the body has gotten rid of quite a lot of water but some of it should be fat being gone too of course! Usually the weight loss is a bit smaller as you get into your diet and plod along, but don't let this discourage you - if you lose weight at a reasonably "normal" pace (1-2 lbs a week) you're much more likely to keep the weight off!
/Ann-Charlotte