Meetings do help, although they aren't for everyone. But statistically speaking, those who attend meetings lose a LOT more weight than those who do not. It is the idea of being accountable and having to weigh in. Honestly, most people have enough nutritional knowledge and know to avoid high-carb, high-fat foods and to try to eat more fruits and vegetables. If that is the case, then why join WW at all, KWIM? Part of the effectiveness of the program is going to meetings and getting weighed once a week. It is so much easier to skip a week online or just not to log in if you had a bad day.
Obviously, people lose weight on WW online, too, but I think that perhaps those are people who either need the information or who have the drive to lose the weight regardless of the program or diet. WW works for me when I have to hold myself accountable and go to meetings. I KNOW what I need to do, and how I need to eat and increase my activity levels, but the issue is DOING it. If I could do it on my own, why would I join WW?