Hi, first of all, you will not lose 'weight' it will be water.
For the past 2 weeks I have only eaten on a saturday and sunday and I have lost NO weight (I am 8.11lbs). As ummmm said, your body goes into starvation mode and stops burning calories and stores fat. You can see yourself losing 'weight' as you feel more and more hungry but you are only losing water and muscle. After 3 days I went to about 8.8lbs then saturday afternoon i was back to 8.11lbs! The first day you start eating properly again, you will go back to the same weight.
Trust me, I have an eating disorder and have tried every 'quick fix' in the book. You will be suffering the whole week only to be disappointed. If you want to feel slimmer, don't bother suffering it. Maybe spend a week having only fruit and veg if you feel you want to restrict yourself, but keep your metabolism going and your sanity, by actually eating something. Or, eat the same stuff, but less of it and go for a 30 minute walk every day for a week and see how you get on.