Background: Etiological hypotheses of eating disorders, anorexia nervosa and bulimia nervosa have not produced informative research for predictably effective treatment. Methods: The rationale for applying a model of allostasis, a dysregulation of reward circuits with activation of brain and hormonal stress responses to maintain apparent stability, is developed for eating disorders. Results: The neurotransmitter systems involved in the allostatic state of a reward system in anorexia nervosa and bulimia nervosa may be similar to those present in drug addiction. Conclusion: The biological vulnerabilities underlying the unique features of eating disorders should be intensively investigated with the advancing techniques in genetics and neuroimaging. Preventing chronicity with early diagnosis and adequate treatment before age 18 is necessary.