One crucial task of early childhood is for a child to develop a secure sense of who they are or, as psychologists call it, a sense of self. This ordinarily occurs naturally through a child's continuing interactions with their parents but if these were inadequate, the child's poorly developed ego capacities are unable to cope with severe stress, particularly when the powerful feelings of adolescence arise.
Then, symptoms occur with low self-esteem being the least severe. More troubling symptoms can include confusion about their identity or even personality disintegration (psychosis).
Anorexic symptoms typically arise in adolescence when there is a need to integrate powerful feelings within the personality. Feeling vulnerable and the loss of control over their body, which the ego's Executive Function provides, the teenager attempts to bolster their self-esteem and gain a sense of control over their body through concrete actions: obsessive focus on their body and diet, and constant exercise.
Because the anorectic person lacks awareness of the connection between these behaviors and their underlying fragmented personality, they tend to resistant psychotherapy. This, despite anorexia having the highest death rate of all the mental health conditions.