In contrast to other mental health disorders, eating disorders have a high prevalence of concomitant medical complications. Specifically, patients suffering from anorexia nervosa (AN) have a litany of medical complications which are commonly present as part of their eating disorders. Almost every body system can be adversely, affected by this state of progressive malnutrition. Moreover, some of the complications can have permanent adverse effects even after there is a successful program of nutritional rehabilitation and weight restoration. Within this article we will review all body systems affected by AN. There is also salient information about both, how to diagnose these medical complications and which are the likely ones to result in permanent sequelae if not diagnosed and addressed early in the course of AN. In a subsequent article, the definitive medical treatment for these complications will be presented in a clinically practical manner.

The pathogenesis of an increasing number of chronic diseases is being attributed to effects of the immune system. However, its role in the development and maintenance of anorexia nervosa is seemingly under-appreciated. Yet, in examining the available research on the immune system and genetic studies in anorexia nervosa, one becomes increasingly suspicious of the immune system’s potential role in the pathophysiology of anorexia nervosa. Specifically, research is suggestive of increased levels of various pro-inflammatory cytokines as well as the spontaneous production of tumor necrosis factor in anorexia nervosa; genetic studies further support a dysregulated immune system in this disorder. Potential contributors to this dysregulated immune system are discussed including increased oxidative stress, chronic physiological/psychological stress, changes in the intestinal microbiota, and an abnormal bone marrow microenvironment, all of which are present in anorexia nervosa.