it's like a food diary, but slightly stricter - you still write down everything you eat, but you MUST measure your syns and healthy extras accurately.
By following an SAS log, you should find out your potential danger areas. I found i eat when I'm bored/tired.
They are good for focussing you again. I found them to be extremely helpful - the first time I did one, I lost 2lbs, and last week, I lost half a pound (but I couldn't really get into it last week and wasn't as strict as I ought to have been!:break_diet