I have, to be honest with you. And just like everyone else, I think the forum's focal point will be limitting, and a little tough to converse on since I lack proper knowledge on health issues...especially sensitive health issues like weight loss. Am also a fat person by the way, so am more on the side of learning actual tips that will help defat myself. I guess I might be pitching one or two answers and comments once in a while.
My personal thoughts and recommendations on the site will be:
Defat is quiet a good idea and given how new the site is, I think it needs compromising. They forum's topics should not be limited to just weight loss. Very few people have actual bases and facts on how to loose weight, which in my opinion should be left mostly for professionals to give tips and advice. Other people with knowledge of weight loss asides health experts are exercise trainers and people who have personally experienced weight loss. Hence, how many trainers and ex-fat people will be available to contribute on the site given how new it is. It needs to get popular before adjusting to specific rules.
Drawing from the above, I will recommend, if asked, that the site focus on general health issues regarding the entire human body instead of weight loss alone. This is the only way it can generate more contents and increase the number of users - the desired goal of every forum.