Can eating soup for a week cause weight loss?

Any kind of a strange or fad diet is not advisable when trying to lose weight. The best way that you can take off weight is to ensure that you are following a few simple rules:

1) Eat a well-balanced diet

2) Keep your calorie intake at a reasonable level (this depends on your age/weight - generally 1500 - 2000 calories per day)

3) Exercise, burning more calories than you have ingested for the day.

4) Drink plenty of water and get some rest!