Eating disorders are serious mental illnesses characterized by persistent disturbances in eating behaviors and associated distressing thoughts and emotions. These conditions extend beyond the more commonly known diagnoses of Anorexia Nervosa (AN) and Bulimia Nervosa (BN), often presenting with varied and complex symptom profiles. Historically, clinicians used the label Eating Disorder Not Otherwise Specified (EDNOS) to categorize presentations that caused significant distress or functional impairment but did not meet the full diagnostic criteria for AN or BN. This categorization described a different clinical pattern that still required specialized treatment.
The Evolution of Terminology: From EDNOS to OSFED
The term EDNOS was a category used in the fourth edition of the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders (DSM-IV). It served as a catch-all for patients who exhibited symptoms of an eating disorder but whose presentation was “not otherwise specified.” EDNOS became the single most frequently diagnosed eating disorder, suggesting the official criteria for AN and BN were too narrow to capture clinical reality.
This high prevalence highlighted the need for a more descriptive diagnostic system. The term was officially retired with the publication of the DSM-5 in 2013, replaced by Other Specified Feeding or Eating Disorder (OSFED). This change aimed to reduce the number of people in the “not otherwise specified” category by creating more specific sub-threshold diagnoses.
OSFED is the current clinical term used in the United States. The diagnostic category of OSFED requires the clinician to specify the reason why the presentation does not meet the full criteria for another disorder, making it a more informative label than EDNOS. This refinement acknowledged that partial-syndrome eating disorders are just as medically and psychologically serious as full-syndrome conditions. Individuals diagnosed with OSFED experience similar levels of psychological distress and medical complications as those with AN or BN.
Diverse Clinical Presentations
OSFED acts as a descriptive category for various forms of disordered eating that do not fit neatly into other diagnostic boxes. The DSM-5 outlines several specific examples that fall under the OSFED umbrella, demonstrating the breadth of this condition. These examples emphasize that an eating disorder does not have to meet every single criterion to be a serious mental illness.
Atypical Anorexia Nervosa
One common presentation is Atypical Anorexia Nervosa. The person meets all the behavioral and psychological criteria for AN, such as intense fear of gaining weight and restrictive eating, but remains at a weight that is within or above the normal range. The diagnosis is assigned despite significant weight loss, underscoring that medical instability is not limited to individuals who are underweight.
Purging Disorder
Another example is Purging Disorder, which involves recurrent purging behaviors (such as self-induced vomiting or misuse of laxatives) to influence weight or shape, but occurs without binge eating. This differs from Bulimia Nervosa, which requires the presence of both binge eating and compensatory behaviors.
Night Eating Syndrome
Night Eating Syndrome is another distinct presentation classified under OSFED, characterized by recurrent episodes of eating after awakening from sleep or consuming an excessive amount of food after the evening meal. Awareness of the eating is typically present, which differentiates it from a sleep-related eating disorder.
The OSFED diagnosis is also applied to subthreshold presentations of other disorders, such as Bulimia Nervosa or Binge Eating Disorder (BED). In these cases, the frequency or duration of the episodes is lower than the full criteria require.
Diagnostic Process and Formal Criteria
A diagnosis of OSFED is assigned when a patient presents with a clinically significant eating disturbance that causes distress or impairment but does not meet the full diagnostic criteria for Anorexia Nervosa, Bulimia Nervosa, or Binge Eating Disorder. The process requires a comprehensive assessment of the patient’s eating behaviors, physical health, and psychological factors. The clinician must systematically evaluate the presentation against the full criteria of the other eating disorders.
The key distinction in the OSFED diagnosis is the requirement for the clinician to specify why the full criteria were not met. For instance, a diagnosis might be “Bulimia Nervosa, low frequency,” meaning the patient engages in binging and compensatory behaviors less than once per week. This systematic approach ensures that the diagnosis is a precise description of the sub-threshold presentation, not a vague default.
This focus on specification helps differentiate OSFED from Unspecified Feeding or Eating Disorder (UFED). UFED is used when the clinician chooses not to specify the reason the criteria are not met, or when there is insufficient information. The severity of the symptoms warrants the OSFED diagnosis and the subsequent need for treatment. OSFED acknowledges that the full spectrum of eating disorders includes many forms that are equally severe.
Treatment and Recovery Pathways
OSFED is a serious condition that carries significant medical and psychological risks, but it is highly treatable with specialized care. The approach to recovery involves a multidisciplinary team, reflecting the complexity of the disorder’s impact. This team typically includes a medical provider, a dietitian, and a mental health professional.
Treatment goals are individualized based on the specific OSFED subtype, such as restoring weight in Atypical Anorexia or addressing purging behaviors. Common therapeutic modalities include Cognitive Behavioral Therapy (CBT), which helps modify the thoughts and behaviors that maintain the disorder. Family-Based Treatment (FBT) is often a first-line intervention for children and adolescents. Recovery focuses on normalizing eating patterns, addressing underlying psychological factors, and developing healthy coping strategies.