[jelly baby]

This, I think, is the Lighterlife diet. You cannot go on this unless you are a minimum of 3 stones overweight. You have to have your GP's approval, he has to sign a form (monthly, I believe) to say you are ok to do it. You are also required to attend weekly group meetings for counselling and to buy the food packs which cost around £66 a week. The counsellors are fully trained and use cognitive behavioural therapy, (CGT) to find out why some people have a bad relationship with food. The drinks course usually takes 12 weeks, after which you go on a weight management course to maintain the weight loss. I know 3 people who have tried this, and all have maintained their losses 18 months later.
It is similar to the Cambridge diet, which is cheaper, but with little or no counselling. It would seem the counselling is the integral part of this diet, and if you don't attend meetings you aren't allowed the food packs.
The way it works is, your body is getting no carbs and only minimal calories and so goes into ketosis (not to be confused with ketoacidosis) and has to run on stored fat. Whilst in this condition you do not feel hunger pangs. You test weekly for ketones. It claims to burn fat at the rate of one pound per day.
If monitored correctly and followed correctly it can be very helpful for the morbidly obese.