What about just printing up some cards with MDA site on it and like Eric said highlighting the success stories? You could say something like here's a site that has a different approach to weight loss and many have had good results with it. Letting them know that this way of eating is based on eating whole unprocessed foods.
I understand how frustrating that would be to be around those that clearly need help and not be able to do something. I think you have to have faith that if you pass on the info some will find their way. My husband is a teacher and he also has constraints on what he can tell his students, there are times when he feels he's not able to reach the kids in a way that he'd like to, but then every now and then he has former students that contact him and tell him how much they got out of his classes.