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
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