I know anorexia is a complex phenomenon. I've been reading on Wikipedia that:
Sociocultural studies have highlighted the role of cultural factors, such as the promotion of thinness as the ideal female form in Western industrialized nations, particularly through the media. There is a necessary connection between anorexia nervosa and culture; culture may be a cause, a trigger, or merely a kind of social address or envelope which determines in which segments of society or in which cultures anorexia nervosa will appear. The strong thesis of this connection is that culture acts as a cause by providing a blueprint for anorexia nervosa. A moderate thesis is that a specific cultural factors trigger the illness which is determined by many factors including family interactions, individual psychology, or biological predisposition. Culture change can trigger the emergence of anorexia in adolescent girls from immigrant families living in highly industrialized Western Societies. People in professions where there is a particular social pressure to be thin (such as models and dancers) were much more likely to develop anorexia during the course of their career, and further research has suggested that those with anorexia have much higher contact with cultural sources that promote weight-loss.
It seems that the mass media can contribute in the diffusion of anorexia. But I wonder if statistics suggest that this disease has got a boom of cases of in the last years.