How long will it take for the cabbage soup diet to ...

It works almost immediately, sending you to the washroom for hours, and causing a pretty severe diarrhea. You will see an immediate weight loss (provided you stick with this diet) within a week, but be advised that most of the weight is water and not fat.

You might want to consider any saner diet.

No, it doesn't work.  You need an eating plan you can stick with for a lifetime, not a week.  Don't waste your time on these fad diets. 

Instead, I would recommend: www.thepaleodiet.com

I think that a really important thing that you should look at is this paragraph.  I think that you should maybe seek another diet, because this looks fake, first of all, and secondly, very dangerous.  Look at this paragraph:

Nutritionists argue that the pounds shed are more likely attributed to the dramatic and dangerous loss in calories and not the proposed fat-burning power found in the cabbage. This diet deprives your body of essential nutrients and has been correlated to difficulty concentrating, feeling light-headed and weak.

If you really want to lose weight in a safe way, try working out at least 3 times a week, and eat 25% less in every meal that you would normally eat.  Another way to do this is like what my father did:  Take every portion that is put in front of you, and eat half (or a little bit more than half) of each portion... this way you will be in shape, and HEALTHY.  Don't forget the working out part though Good luck and stay healthy.