Ignore what you "lost" the first week, just eating less food (and having less food in your body) will show a 4 or 5 pound drop in the first week, but it is not a "real" weight loss. Everybody gets that the first week.
And once a diet starts then 1 or 2 pounds a week is about right (some weeks no loss) so you should not start worrying.
Remember weight can be put on over many months and years so it is not going to come off in a few weeks.
Any weight loss program should be thought of as a many months or years thing, not a "quick fix".
Just eat well and do some simple exercise and the weight will gradually come off.
I get sick of all these books and fancy diets, there is no "magic" solution.
You put weight on if you eat too much and don't exercise, if you eat less and exercise weight will (slowly) come off. It is that simple.
But DON'T rush it, it can take months or years.