A genetic vulnerability is involved in the development of anorexia nervosa. The risk is greatest for female relatives and the incidence is higher in Western culture. The culture or environment does not cause eating disorders but it ‘feeds’ their triggers or symptoms through the promotion of a slim and fi t body physique – the message being that only people who are slim and fi t are desirable and worthy. The combination of genetic and environmental factors means it is not uncommon for two sisters to have an eating disorder. In one out of 14 families, another family member will be affected. This causes additional diffi culties.