It is very possible to lose weight following CFG. It all has to do with portion size. You would probably be very surprised to see an actual "portion" size. I can't remember off hand (I don't follow portion sizes and hence I am overweight!) but a serving of meat should be about the size of your fist, I believe. I have an appointment with dietician next month and will be able to offer more info then. My coworker has already seen her and her weight loss strategies are based on the CFG, caloric intake and exercise.
I know I was recently put on the diabetic diet due to GD, and let me tell you, it really worked as I have lost tons of weight. No one would tell I just had a baby (until they look at my tummy that is, lol). Either way, my doc was telling me that this is a good diet to follow even if not diabetic. Having a hard time following it now with a 3 month old, but I can say that my portions have indeed been reduced.