Bizi, I wouldn't worry about putting on some weight. Eating a bit too much sometimes happens over the Christmas-New Year period.
I tried AA a couple of times but it did not work for me, maybe because I am not religious. On the other hand somebody who I met when I used to go to a mood disorders therapy group found that it was good for her; she is not religious either.
I suspect that a lot depends on the social dynamics of the group.