The diagnosis and treatment of anorexia nervosa (AN) in children and adolescents has some commonality but also differs from that of this condition in adults. A new understanding of AN is emerging: research data from the fields of epidemiology, genetics, and brain biology, suggest that there may be an underlying brain diathesis predisposing towards AN. It is now proposed that that what starts as a harmless diet, once it turns into a more prolonged food restriction may trigger an eating disorder in a genetically neurobiologically predisposed population. The condition may be then perpetuated by the biochemical changes induced by weight loss, ketosis, and the impact of the ensuing malnutrition on the brain (starvation illness). This change of paradigm from a psychological understanding to a neurobiological conceptualization calls for an early intervention to assure nutritional rehabilitation as soon as an eating disorder is suspected in children, without needing to wait for all the classical features of the diagnosis as seen in adults. This new model is agnostic about the origins of the disease and questions the classic assumption of "an underlying family pathology". It gives strong support to treatments such as Family Based Treatment, also referred to as the "Maudsley method". Essentially this consists of empowering parents to monitor and supervise the nutritional rehabilitation of their children. Hence pediatricians no longer need to be bystanders when treating these children and adolescents. They now have a clearly defined role: early diagnosticians, clinical monitors (of potential medical complications), nutrition advisors, and as members of a multidisciplinary team, patient and family advocates and educators.