While eating disorders have long been thought of as having a sociocultural origin, more and more research have proved this to be wrong. While social and cultural factors surely do play a role, the most interesting factor is by far genetics. For this question, I will be focusing solely on the disorder \textit{anorexia nervosa} (AN) as the information I found was largely based on it.
European studies have consistently shown that genetics play a major part in whether a person will suffer from anorexia nervosa. Only 0.5\% of the general population is likely to develop the disorder, but this number increases by eleven-fold when a family member has the illness. Women are also more likely to have it.