Any drastic reduction in calories (like the cabbage soup diet) will result in weight loss so, yes, it can help one lose weight in the short term...but it will usually be temporary. I'm sure the proponents of this diet all stress the weight loss, but don't say anything about long-term sustained weight loss (because it won't happe
10 pounds weight loss in 7 days does sound tempting to many people, but it's not possible that it is all fat loss, as Dela said. If it were possible to lose and maintain that much weight in that period of time, it would be possible to gain that much in that period of time. That's why it's always recommended to lose 1-2 pounds a week, which is sustainable, and insures that it's mostly fat that is being lost.
Any kind of eating more simply can be used as a cleanse (or way of lightening the load on the body so it can put more energy into cleaning and repairing).
Cabbage soup is a healthy food, and good to include in one's regular diet, but not something I'd want to eat exclusively or long term.