So they have a new system and declare proudly "we're so confident in our new approach, if you lose 10lbs in your first 8 weeks, we'll give you your money back"
This just doesn't work as a money back guarantee does it? Money back guarantees are supposed to work on the basis of "we're confident that this event is so unlikely, if it happens, we'll lose profit by giving you your money back".
I understand that ww can't say "if you don't lose 10lbs, we'll give you your money back", which would be the normal way to do it, as everyone would just carry on eating donuts! But switching it round doesn't work either. Just makes me think that you won't lose that much as they wouldn't want to lose all that money. Drives me nuts every time I see the advert.