Anorexia nervosa (AN) is a serious eating disorder characterized by a persistent restriction of energy intake, which leads to a significantly low body weight. Individuals with this condition demonstrate an intense fear of gaining weight or becoming fat, even when they are severely underweight. To better describe the diverse ways this disorder presents, clinicians and researchers classify AN into two distinct subtypes based on the specific behaviors used to prevent weight gain. Understanding these different behavioral patterns is important for both accurate diagnosis and the development of effective, personalized treatment strategies.
Shared Diagnostic Criteria for Anorexia Nervosa
Regardless of the behavioral subtype, all individuals diagnosed with anorexia nervosa must meet three core diagnostic criteria. The first criterion involves the restriction of energy intake relative to the body’s requirements, resulting in a significantly low body weight for the person’s age, sex, and developmental trajectory. This low body weight is a defining physiological feature of the disorder.
A second defining feature is an intense fear of gaining weight or becoming fat, or exhibiting persistent behavior that actively interferes with weight gain, even though the individual is already at a significantly low weight. This fear often intensifies as the person loses more weight.
The third criterion is a disturbance in the way one’s body weight or shape is experienced, often including a denial of the seriousness of the current low body weight. This body image distortion means that self-evaluation is unduly influenced by body shape and weight, and the person may not recognize the medical severity of their physical state.
The Restricting Type
The Restricting Type of anorexia nervosa (AN-R) is diagnosed when, during the last three months, the individual has not engaged in recurrent episodes of binge eating or purging behavior. Weight loss in this subtype is achieved primarily through stringent methods like dieting, fasting, and/or excessive exercise. These individuals often exhibit highly controlled, rigid eating habits, focusing on meticulously counting calories and minimizing food intake.
The medical complications associated with AN-R are typically consequences of chronic starvation and malnutrition. These can include severe low blood pressure (hypotension), low body temperature, and a higher risk of conditions like osteopenia and osteoporosis due to prolonged nutritional deprivation. The psychological presentation of AN-R is often characterized by high levels of control and perfectionism, with a focus on self-discipline regarding food and activity.
The Binge-Eating/Purging Type
The Binge-Eating/Purging Type (AN-B/P) is diagnosed when the individual has engaged in recurrent episodes of binge eating or purging behaviors within the last three months, despite meeting the core criteria for anorexia nervosa. Purging behaviors are actions taken to compensate for food intake, such as self-induced vomiting or the misuse of laxatives, diuretics, or enemas. Individuals with this subtype still exhibit severe food restriction, but they also experience cycles of binging and/or purging.
The presence of these compensatory behaviors creates a profile distinct from AN-R. Purging can lead to unique and acute medical risks, including severe electrolyte imbalances that can cause life-threatening cardiac arrhythmias. Other physical signs of this subtype may include dental enamel erosion from repeated vomiting and swelling of the salivary glands.
Differentiation and Tailored Treatment Approaches
The distinction between the two AN subtypes informs the anticipated health risks and the necessary focus of therapeutic intervention. Individuals with AN-B/P often exhibit higher rates of co-occurring conditions, such as impulsivity, mood instability, and substance use disorders, compared to those with AN-R, suggesting a need for specific psychological approaches that address these behavioral and emotional complexities.
For AN-B/P, treatment plans must address both restriction and the impulsive behaviors associated with binging and purging. Therapeutic interventions may prioritize emotion regulation and distress tolerance strategies, sometimes incorporating principles from Dialectical Behavior Therapy (DBT) alongside specialized Cognitive Behavioral Therapy (CBT-E). Conversely, treatment for AN-R often focuses on challenging rigid, perfectionistic thought patterns and normalizing eating behavior to restore nutritional health and weight. Medical complications also dictate the immediate clinical focus, with AN-B/P requiring close monitoring for electrolyte disturbances, while AN-R may necessitate a focus on bone health and cardiovascular stability.