The Cabbage Soup Diet is a quick fix diet for those people who only have a few pounds to lose. Unlike most other dietary programmes, it does not encourage a change in the way you eat, long term it is more a way of shifting surplus pounds in the short term.
Many people go on the Cabbage Soup Diet in the week leading up to a big event where they want to that little bit svelter.
The diet program lasts for seven days (and must not be exceeded) and, for many people, a week on a strict diet is something achievable if they dont have mammoth amounts of weight to lose.
A lot of the weight loss you see will be water, but many people find they do drop a dress size after having been on the seven day programme.
Basically, you eat as much cabbage soup as you want for a week, plus a very limited amount of other foods. To stay on the programme for longer than a week will be counter-productive and will affect your health and energy levels. Source