Source: Abnormal Psychology Textbook (University of Florida)
Difficulty: Intermediate | Prerequisites: Basic understanding of DSM-5 diagnostic framework
Tags: anorexia nervosa, bulimia nervosa, eating disorders, DSM-5, binge-purge, restricting type, compensatory behaviors, body image distortion, amenorrhea, abnormal psychology chapter 12
Eating disorders sit at the intersection of biology, psychology, and culture. This chapter covers the major diagnostic categories in the DSM-5, their causes, and how they are treated. If you are coming in cold, know that eating disorders are not simply about food. They involve distorted thinking about body image, deep emotional distress, and serious medical consequences, including death. You should already be familiar with basic DSM-5 structure (how disorders are categorised, what "criteria" means) before diving in.
Anorexia nervosa involves self-starvation and an intense fear of gaining weight despite being dangerously underweight. Bulimia nervosa involves cycles of binge eating followed by compensatory behaviours (vomiting, laxatives, excessive exercise) in someone who is typically at or near normal weight. Both are more common in women, tend to begin in adolescence, and carry serious medical and psychological risks.
Most people who meet the criteria for one eating disorder will migrate between diagnoses over time, meeting the criteria for two or more disorders at different points. Some individuals show behaviours and concerns characteristic of eating disorders without meeting the full diagnostic threshold for any single one. These individuals may receive a diagnosis of "other specified feeding or eating disorder."
Anorexia nervosa
A disorder characterised by self-starvation, significantly low body weight relative to age and height, intense fear of weight gain, and distorted body image. In simple terms, the person restricts food intake to a dangerous degree and still believes they need to lose more weight.
Bulimia nervosa
A disorder defined by repeated episodes of binge eating followed by inappropriate compensatory behaviours (purging, fasting, excessive exercise) to prevent weight gain. Think of it as a cycle: eat large amounts in a short period, then try to undo it.
Amenorrhea
The absence of menstruation. In anorexia, starvation can cause periods to stop. DSM-5 removed this as a required criterion because some individuals with anorexia still menstruate.
Binge eating
Eating an amount of food in a discrete period (typically one to two hours) that is clearly larger than what most people would eat in similar circumstances, accompanied by a sense of loss of control. In simple terms, it is not just overeating at a meal; the person feels they cannot stop.
Compensatory behaviours
Actions taken to prevent weight gain after eating. These include self-induced vomiting, misuse of laxatives or diuretics, fasting, and excessive exercise.
Body mass index (BMI)
Body weight in pounds multiplied by 703, then divided by height in inches squared. Used clinically to gauge severity of anorexia and to define obesity thresholds.
Restricting type (anorexia)
A subtype of anorexia nervosa where weight loss is achieved primarily through dieting, fasting, or excessive exercise, without regular binge-purge episodes.
Binge/purge type (anorexia)
A subtype of anorexia nervosa where the individual periodically binges or purges. The key distinction from bulimia is that the person remains substantially below healthy body weight.
Individuals starve themselves or subsist on very little food for extended periods, yet remain convinced they need to lose weight
Body weight is significantly below the minimum expected for age and height
Distorted body image: the person often believes they are large even when dangerously thin
Intense fear of gaining weight or becoming fat drives the restriction
Self-worth becomes tied almost entirely to control over eating and weight loss
Despite chronic fatigue from weight loss, many continue to exercise excessively and maintain demanding schedules at work or school
Elaborate rituals around food are common (cutting food into tiny pieces, eating in a specific order, hoarding food)
Mild: BMI greater than or equal to 17
Moderate: BMI 16 to 16.99
Severe: BMI 15 to 15.99
Extreme: BMI below 15
Severity is also assessed using clinical symptoms, degree of functional disability, and need for supervision.
Restricting type
The person refuses to eat or engages in excessive exercise to prevent weight gain. Some go without food for days; others eat only very small amounts to stay alive or to satisfy pressure from others.
Binge/purge type
The person periodically binges or purges (induces vomiting). Crucially, the binges are typically small amounts of food that feel excessive to the individual, unlike the objectively large binges seen in bulimia. The distinguishing feature from bulimia is that body weight remains substantially below healthy range.
More common in women than men
More prevalent among white populations than Black or Hispanic populations, partly linked to greater acceptance of the thin ideal promoted by Western media
Cultures that do not emphasise thinness as a female ideal have lower rates
Higher incidence since the early 20th century
In some Asian countries, individuals with anorexia do not report distorted body image (they acknowledge being very thin) but still refuse to eat. DSM-5 expanded criterion B to include persistent behaviour that interferes with weight gain, not only expressed fear of gaining weight
Typical onset in adolescence or young adulthood
Median time from onset to remission: 7 years for women, 3 years for men (even with treatment)
At 10 to 15 years after onset, roughly 70% no longer meet diagnostic criteria, but many continue to have eating-related difficulties or comorbid conditions such as depression
Binge/purge type is associated with more comorbid psychopathology than restricting type, including impulsivity, suicidality, self-harm, and a more chronic course
DSM-4 required the individual to be at least 15% below normal body weight and required amenorrhea in women
DSM-5 loosened both criteria (removed amenorrhea, broadened the weight criterion), so prevalence rates under DSM-5 are expected to be higher
Death rate of 5 to 9%
Cardiovascular complications: bradycardia (slow heart rate), arrhythmia, heart failure
Acute stomach expansion that can lead to rupturing
Kidney damage
Impaired immune system, increasing susceptibility to illness
Higher suicide rate
Amenorrhea leads to low oestrogen, which weakens bones
Defined by uncontrolled eating (bingeing) followed by behaviours designed to prevent weight gain
A binge occurs over a discrete period (one to two hours) and involves an amount of food clearly larger than what most people would eat in that time
Caloric intake during a binge varies: some consume 3,000 to 4,000 calories, others 1,000 to 2,000
Even smaller amounts count as binges if the person feels they have violated their own dietary rules and cannot control their eating
The DSM-5 includes lack of control as a diagnostic criterion for this reason
Compensatory behaviours: self-induced vomiting (most common), laxative abuse, diuretics, purging medications, fasting, excessive exercise
Self-evaluation is heavily shaped by body shape and weight
Unlike anorexia, people with bulimia do not tend to show gross body image distortion. They see their reflection relatively accurately but remain intensely dissatisfied
Mild presentations: average of 1 to 3 episodes of compensatory behaviour per week
Extreme forms: average of 14 or more episodes per week
Much more common in females than males
Men with bulimia tend to focus on a lean, muscular look rather than thinness, and are more likely to use excessive exercise as their compensatory method
More common among white populations and in Westernised cultures
Rates increased after the second half of the 20th century but have been roughly stable since 1990 in the US, Europe, and Australia
Onset is most often in adolescence
DSM-4 required binge/purge behaviours at least twice per week; DSM-5 reduced this to once per week, so future prevalence figures are expected to be higher
Electrolyte imbalance from chronic vomiting, laxative abuse, and diuretic abuse, which can lead to heart failure
Dental erosion from repeated vomiting (often discovered by dentists)
Death rate roughly double that of the general population (lower than anorexia, but still elevated)
Suicide rate 7.5 times higher than the general population
Tends to be chronic: about 50% show remission, the other half continue to experience symptoms
Frequent purging is a predictor of poorer outcomes
Students often think bulimia and the binge/purge subtype of anorexia are the same thing. They are not. The key distinction is weight: people with the binge/purge subtype of anorexia are significantly underweight, while people with bulimia are typically at or near normal weight.
Students sometimes assume amenorrhea is still required for an anorexia diagnosis. DSM-5 removed it.
A common error is believing that a binge must involve huge quantities of food. Under DSM-5, a binge can involve a smaller amount if the person feels a loss of control and believes they have broken their dietary rules.
Students often confuse body image distortion across disorders. People with anorexia typically have severe distortion (they see themselves as large when emaciated). People with bulimia generally see their body fairly accurately but are deeply dissatisfied.
⚠️ Know the BMI severity cut-offs for anorexia (17, 16, 15, below 15).
⚠️ Be able to distinguish the restricting type from the binge/purge type of anorexia, and both from bulimia nervosa.
⚠️ Understand how DSM-5 criteria differ from DSM-4 for both anorexia and bulimia and why prevalence rates are expected to change.
⚠️ The death rate for anorexia (5 to 9%) is a commonly tested statistic. Bulimia's mortality is lower but still elevated.
⚠️ Cultural and demographic patterns (gender, ethnicity, Westernisation) are frequently examined.
True or false: DSM-5 requires amenorrhea for a diagnosis of anorexia nervosa.
Fill in the blank: A BMI of ______ or below is classified as extreme severity in anorexia nervosa.
True or false: People with bulimia nervosa are typically significantly underweight.
Fill in the blank: The suicide rate in bulimia nervosa is approximately ______ times higher than the general population.
True or false: The binge/purge subtype of anorexia involves objectively large binges, similar to those in bulimia.
Answers: 1. False. 2. Below 15. 3. False (they are typically normal weight or somewhat overweight). 4. 7.5. 5. False (the binges are often small amounts that feel excessive to the individual).
Q: What is the key feature that distinguishes the binge/purge subtype of anorexia nervosa from bulimia nervosa?
A: Body weight. In the binge/purge subtype of anorexia, the individual remains substantially below healthy body weight. In bulimia, the individual is typically at or near normal weight.
Q: Name two criteria that DSM-4 required for anorexia nervosa that DSM-5 relaxed or removed.
A: DSM-4 required body weight at least 15% below normal and required amenorrhea in women. DSM-5 broadened the weight criterion to "significantly low" and removed the amenorrhea requirement.
Q: Why does the DSM-5 include "lack of control" as part of the definition of a binge?
A: Because a binge is not defined solely by the amount of food consumed. A person may eat a relatively small amount but feel they have violated their own dietary rules and are unable to stop. The subjective experience of lost control is central to the diagnosis.
Q: List three medical consequences of anorexia nervosa.
A: Cardiovascular complications (bradycardia, arrhythmia, heart failure), kidney damage, and weakened bones due to low oestrogen from amenorrhea. (Other valid answers: stomach rupture, impaired immune system.)
Q: How does body image distortion differ between anorexia and bulimia?
A: People with anorexia typically have severe distortion, perceiving themselves as large when they are dangerously thin. People with bulimia tend to perceive their body relatively accurately but are intensely dissatisfied with their shape and weight.
This material connects directly to mood disorders (Chapter on Depression), since depression is a common comorbidity for both anorexia and bulimia, and depressive symptoms can both precede and follow from eating disorders. The role of sociocultural pressures also ties into social psychology and the broader discussion of how media and cultural norms shape behaviour. The neurotransmitter involvement (serotonin, dopamine) links to biological bases of behaviour covered in earlier chapters.
anorexia nervosa, bulimia nervosa, binge-purge, restricting type, compensatory behaviour, self-induced vomiting, laxative abuse, amenorrhea, body image distortion, DSM-5 eating disorders, BMI severity, electrolyte imbalance, thin ideal, abnormal psychology chapter 12, eating disorder subtypes, eating disorder mortality, eating disorder gender differences, eating disorder cultural factors