LOL I did it a few years ago and lost 2 stone, mum did it last year and lost 4 stone so it does work. Sadly I put it all on again and some!
You are weighed at your first class and your points worked out eg if you are 12 stone you might be allowed 22 points a day. You then deduct everything you eat from those 22 points. Say a mars bad has 4 points (don't quote me) that would be 22-4=18points left. Some things are point free like fruit, veg and diet drinks.
I found it easy to use as you could eat and drink what you liked as long as you deducted the points so if you fancied a massive cream cake you could have one.
Hope this helps. xxx