My mum said that she couldn't see how it works either. I just told her to stop looking!!! Now she can look all she wants - at the weight dropping off, week after week!!!!!
But seriously, reasons it works:
Limits high fat / high sugar foods - Syns available.
Limits cereals / breads - HEX b's available
Limits dairy intake - HEX a's available
By encouraging you to fill up on 'free food' ie food that makes you feel fuller, for not too high an amount of calories. This also gets you out of the 'binge' mentality as you are never 'absolutely STARVING' when it comes to meals.
Basically, it's a low fat/low sugar/reduced calorie diet, that makes you eat healthily, enjoy a range of foods and never feel deprived. ie. Makes you eat like a 'NORMAL' person.
Having said all that, usually I don't think about it and just enjoy the rewards !!!!!!