Anorexia nervosa is a multidimensional disorder, the causes of which are also numerous. Sociocultural factors play a key role in its etiology, though it is the biological factors that lead to the medical pathology and act as signzficant primary and secondary causal agents. A review of the literature reveals the existence of predisposing (genetic, of maturation) and maintaining (biochemical, gastric, metabolic and growth) biological factors, all of which are related to malnutrition.