Source: Abnormal Psychology, University of Florida
Difficulty: Intermediate | Prerequisites: Familiarity with DSM-5 structure and basic diagnostic terminology.
Tags: eating disorders, anorexia nervosa, bulimia nervosa, binge-eating disorder, DSM-5, abnormal psychology, OSFED, night eating disorder, obesity, body image, amenorrhea, BMI
Eating disorders sit at the intersection of biology, psychology, and culture. They are among the most physically dangerous psychiatric conditions, with anorexia nervosa carrying the highest mortality rate of any mental disorder. This chapter covers the major eating disorder diagnoses in the DSM-5, their prevalence, course, and medical consequences, before moving (in Parts 2 and 3) into causes and treatment. You should already be comfortable with how the DSM-5 organises diagnostic criteria and severity specifiers.
Society ties weight to self-worth, and eating disorders take that link to a clinical extreme. The three primary DSM-5 diagnoses are anorexia nervosa (restriction leading to dangerously low weight), bulimia nervosa (binge-purge cycles at roughly normal weight), and binge-eating disorder (recurrent binges without compensatory behaviour). Each has distinct criteria, but individuals often migrate between diagnoses over time.
Anorexia nervosa
Restriction of energy intake leading to significantly low body weight, combined with intense fear of weight gain and a disturbance in how body weight or shape is experienced. DSM-5 defines "significantly low" as a BMI of 18.5 or below, though clinical judgement also considers symptoms and functional disability.
In simple terms, the person starves themselves while remaining convinced they need to lose more weight.
Restricting type (anorexia)
Subtype in which, over the past three months, the individual has not engaged in recurrent binge eating or purging. Weight loss comes through dieting, fasting, or excessive exercise.
Think of it as: pure restriction with no binge-purge episodes.
Binge-eating/purging type (anorexia)
Subtype in which the individual has engaged in recurrent episodes of binge eating or purging within the last three months, while still maintaining a significantly low body weight.
In simple terms, the person both starves and purges, distinguishing them from bulimia by their dangerously low weight.
Bulimia nervosa
Recurrent episodes of binge eating followed by inappropriate compensatory behaviours (self-induced vomiting, laxative misuse, fasting, or excessive exercise), occurring at least once a week for three or more months. Self-evaluation is unduly influenced by body shape and weight.
Think of it as: the binge-purge cycle at or near a normal weight.
Binge eating
Eating, within a discrete period of time (e.g. a two-hour window), an amount of food that is clearly larger than what most people would eat under similar circumstances, accompanied by a sense of loss of control.
In simple terms, the person feels they cannot stop eating or control how much they consume during the episode.
Binge-eating disorder (BED)
Recurrent binge-eating episodes associated with three or more behavioural markers (eating rapidly, eating until uncomfortably full, eating when not hungry, eating alone due to embarrassment, feeling disgusted or guilty afterwards), with marked distress, occurring at least once a week for three months. Crucially, there is no regular compensatory behaviour.
Think of it as: bulimia without the purging.
Amenorrhea
Cessation of menstrual periods, historically associated with anorexia nervosa. The DSM-5 removed this as a diagnostic requirement.
Other specified feeding or eating disorder (OSFED)
A diagnostic category for presentations that cause clinically significant distress or impairment but do not meet the full criteria for anorexia, bulimia, or BED. Includes atypical anorexia nervosa and low-frequency bulimia. Formerly called EDNOS in DSM-IV.
In simple terms, a real and serious eating disorder that falls just outside the formal boxes.
Night eating disorder
Recurrent episodes of excessive eating after dinner and into the night, with associated distress, insomnia, and morning anorexia. Introduced in DSM-5 under OSFED. Distinct from sleep-eating, in which the person is not awake.
Partial-syndrome eating disorders
Presentations that include significant weight or body-image concerns and disordered eating but do not meet full criteria for any specific diagnosis. Despite falling short of a formal diagnosis, 90% of individuals with partial-syndrome presentations had a diagnosable psychiatric disorder by their early 20s.
Body weight is significantly below what is minimally normal for age and height (BMI ≤ 18.5, plus clinical judgement)
Distorted body image: individuals often believe they are overweight despite severe emaciation
Self-worth becomes entirely contingent on controlling eating and losing weight
Chronic fatigue is common
DSM-5 diagnostic criteria (Criterion A, B, C):
A: Restriction of energy intake leading to significantly low body weight, in the context of age, sex, developmental trajectory, and physical health
B: Intense fear of gaining weight or persistent behaviour that interferes with weight gain, even at significantly low weight
C: Disturbed body-image perception, undue influence of weight/shape on self-evaluation, or persistent failure to recognise the seriousness of the low weight
Prevalence:
0.9% of adult women, 0.3% of men, 0.3% of adolescent girls (DSM-IV figures, likely higher under DSM-5's broader criteria)
More common in white populations than in African American or Hispanic groups, partly reflecting cultural internalisation of the thin ideal
Cultures that do not value thinness show lower rates
Rates have increased substantially since the early 20th century
Course:
Typical onset in adolescence or young adulthood
Median time to remission: 7 years for women, 3 years for men (even with treatment)
At the 10 to 15 year mark, roughly 70% no longer meet diagnostic criteria, but many retain eating-related difficulties or depression
The binge-purge subtype tends toward more comorbid psychopathology (impulsivity, suicidal behaviour, self-harm) and a more chronic illness course
Medical consequences and mortality:
Death rate of 5–9%
Cardiovascular complications: bradycardia, arrhythmia, heart failure
Gastric rupture from acute stomach expansion
Bone weakness (low oestrogen reduces bone density in women)
Kidney damage, impaired immune function
Suicide rate 31 times the general population
DSM-5 cultural note: Criterion B was broadened to include not only overt fear of weight gain but also persistent behaviour that interferes with weight gain, acknowledging that in some cultures, individuals engage in severe restriction without expressing weight-related fears in Western terms.
Core pattern: uncontrolled eating (bingeing) followed by compensatory behaviours to prevent weight gain
Binge size varies: some consume 3,000–4,000 calories in one sitting; others 1,200–2,000
"Subjective binges" also count: the person feels they have violated a dietary rule and lost control, even if the quantity consumed is not objectively large
Men with bulimia are more likely to use excessive exercise as the compensatory method
DSM-5 diagnostic criteria (A through E):
A: Recurrent binge eating (large amount in discrete time + loss of control)
B: Recurrent inappropriate compensatory behaviours (vomiting, laxatives, diuretics, fasting, excessive exercise)
C: Both behaviours occur at least once a week for 3+ months
D: Self-evaluation unduly influenced by body shape and weight
E: Disturbance does not occur exclusively during episodes of anorexia nervosa
Severity specifiers:
Mild: 1–3 compensatory episodes per week
Extreme: 14+ episodes per week
Prevalence:
0.5% in adults, 0.9% in adolescents
More common in females, and more common in white and Westernised populations
Rates increased significantly in the second half of the 20th century, then stabilised around 1990 in the US, Europe, and Australia
Course:
Onset typically in adolescence
Tends to be chronic: 15 years after onset, 50% still met diagnostic criteria
Frequent purging predicts poorer outcomes
Medical consequences and mortality:
Death rate approximately double the general population (lower than anorexia, but still elevated)
Electrolyte imbalance, which can lead to heart failure
Suicide rate 7.5 times the general population
Resembles bulimia but without regular compensatory behaviours
Was a proposed condition in DSM-IV; promoted to a full diagnosis in DSM-5 after 20 years of research
Some individuals eat continuously throughout the day with no planned mealtimes; others have discrete, large-volume binge episodes triggered by stress, anxiety, or depression
Eating is often rapid, almost trance-like
Individuals are frequently significantly overweight and feel shame and disgust about their bingeing
Common history of repeated dieting, weight-control programme enrolment, and family obesity
Roughly 30% of people in weight-loss programmes may meet criteria for BED (versus 2–3.5% in the general population)
DSM-5 diagnostic criteria (A through E):
A: Recurrent binge eating (same definition as bulimia)
B: Binge episodes associated with 3+ of: eating rapidly, eating until uncomfortably full, eating when not hungry, eating alone from embarrassment, feeling disgusted/depressed/guilty afterwards
C: Marked distress regarding binge eating
D: Binge eating at least once a week for three months
E: Not associated with regular compensatory behaviour and does not occur exclusively during bulimia or anorexia
Prevalence:
Somewhat more common in women, but the gender gap is smaller than for anorexia or bulimia
Course:
More chronic than bulimia, with a typical duration of 8–14.4 years
High rates of comorbid depression, anxiety, alcohol abuse, and personality disorders
Atypical anorexia nervosa:
All criteria for anorexia are met, but the individual's weight remains within or above the normal range
Bulimia nervosa of low frequency and/or limited duration:
All bulimia criteria met except that binge eating and compensatory behaviours occur less than once a week or for fewer than three months
Night eating disorder:
Excessive eating after dinner and into the night, with distress, insomnia, and morning appetite suppression
Introduced in DSM-5
Often begins in early adulthood and tends to be long-lasting
Associated with overweight and depression
Distinct from sleep-eating (the person is fully awake)
Partial-syndrome eating disorders:
Do not meet full criteria but still involve significant weight concern and impaired functioning
90% had a diagnosable psychiatric disorder by their early 20s
Lower self-esteem, poorer social relationships, poorer physical health, and higher unemployment rates than those without eating disorder symptoms
EDNOS (DSM-IV):
The predecessor category to OSFED
Affected roughly 5% of the population
Tended to be as severe and persistent as full-diagnosis anorexia or bulimia
Diagnostic migration: most individuals who meet criteria for one eating disorder will "migrate" between two or more diagnoses at different points in their life.
Defined as a BMI of 30 or above
Not classified as a mental disorder in DSM-5, but included in the chapter because of its relationship to eating behaviour and mental health
Associated with coronary heart disease, hypertension, stroke, type 2 diabetes, and certain cancers
Accounts for 5–7% of all US healthcare costs
Roughly one-third of American adults and 17% of American children are obese
Racial disparities: African Americans have the highest rates, followed by Hispanics, then whites
Rising internationally alongside increases in standard of living and access to ultra-processed food
Ultra-processed foods may produce addiction-like responses: obese individuals show heightened reward-area brain activity when viewing food images but reduced activity during actual consumption (craving, tolerance, and withdrawal patterns)
Genetic factors account for a substantial portion of variability (number of fat cells, fat storage tendency, brain reward responses to food), but genes interact with environmental factors
Weight-loss interventions:
Pharmacological: sibutramine (Meridia), orlistat (Xenical), rimonabant (Acomplia), each with modest efficacy (≤11 lbs over 1–4 years) and notable side effects
Low-calorie diets (900–1,200 kcal/day) with prepackaged portions
Bariatric surgery for BMI ≥ 40 (yields 25–30% weight loss)
Behavioural recommendations: 30 minutes daily activity, nutrient-dense food choices, environmental restructuring to support healthier options
Students sometimes assume anorexia and bulimia are mutually exclusive. They are not: anorexia has a binge-eating/purging subtype, and individuals frequently migrate between diagnoses over time.
Amenorrhea is often still cited as a core feature of anorexia. The DSM-5 removed it from the diagnostic criteria.
Binge-eating disorder is sometimes dismissed as "just overeating." The DSM-5 requires marked distress, loss of control, and specific associated features (eating rapidly, eating alone from embarrassment, etc.).
Obesity is frequently confused with an eating disorder. It is not classified as a mental disorder in the DSM-5, though it can co-occur with BED and other psychiatric conditions.
⚠️ Know the three DSM-5 criteria (A, B, C) for anorexia and be able to distinguish the restricting type from the binge-eating/purging type.
⚠️ Be able to explain why DSM-5 broadened Criterion B for anorexia (cultural sensitivity: some individuals restrict without expressing overt fear of weight gain).
⚠️ Understand the key difference between bulimia and BED: the presence or absence of regular compensatory behaviours.
⚠️ Distinguish the binge-eating/purging type of anorexia from bulimia: body weight is the differentiator (significantly low weight = anorexia subtype; near-normal weight = bulimia).
⚠️ Remember that BED was only elevated to a full DSM-5 diagnosis (it was a "proposed condition" in DSM-IV).
⚠️ Mortality stats are commonly tested: 5–9% death rate for anorexia, 31x suicide rate; 2x death rate for bulimia, 7.5x suicide rate.
⚠️ Obesity is not a DSM-5 mental disorder. Know why it is discussed in the eating disorders chapter anyway (associated with mental disorders, risk factor, psychotropic medication side effect).
True or false: Amenorrhea is still a required diagnostic criterion for anorexia nervosa in the DSM-5.
Fill in the blank: The key feature that distinguishes binge-eating disorder from bulimia nervosa is the absence of regular __________ behaviours.
True or false: Binge-eating disorder was a fully recognised diagnosis in the DSM-IV.
Fill in the blank: A BMI of __________ or below is the DSM-5 benchmark for "significantly low body weight" in anorexia.
True or false: Obesity is classified as a mental disorder in the DSM-5.
Answers: 1. False. 2. Compensatory. 3. False (it was a proposed condition). 4. 18.5. 5. False.
Q: What are the three core DSM-5 criteria (A, B, C) for anorexia nervosa?
A: A: Restriction of energy intake leading to significantly low body weight. B: Intense fear of gaining weight or persistent behaviour interfering with weight gain. C: Disturbance in body-image perception, undue influence of weight/shape on self-evaluation, or failure to recognise the seriousness of low weight.
Q: How does the binge-eating/purging type of anorexia differ from bulimia nervosa?
A: Both involve binge-purge behaviour, but in the anorexia subtype the individual's body weight remains significantly below normal (BMI ≤ 18.5), whereas in bulimia the person is typically at or near a healthy weight.
Q: Why did the DSM-5 broaden Criterion B for anorexia nervosa?
A: To account for cultural variation. In some cultures, individuals engage in severe restriction and behaviours that interfere with weight gain without explicitly stating a fear of becoming fat. The broadened criterion captures persistent behaviour, not just expressed fear.
Q: What distinguishes binge-eating disorder from bulimia nervosa according to DSM-5 criteria?
A: In BED, binge eating occurs without recurrent inappropriate compensatory behaviours (vomiting, laxative misuse, fasting, or excessive exercise). Bulimia requires both binges and compensatory behaviours.
Q: What is OSFED, and what are two examples of presentations it captures?
A: OSFED (Other Specified Feeding or Eating Disorder) captures clinically significant eating-disorder presentations that do not meet full criteria for anorexia, bulimia, or BED. Examples include atypical anorexia nervosa (all anorexia criteria met but weight is within or above normal range) and low-frequency/limited-duration bulimia nervosa.
Q: Is obesity classified as a mental disorder in DSM-5? Why is it discussed in the eating disorders chapter?
A: No. It is discussed because it is associated with numerous mental disorders, is a risk factor for developing some mental disorders, and can result from psychotropic medication side effects.
This material connects directly to mood disorders (depression is highly comorbid with all three eating disorders and is a risk factor for their development). It also links to the personality disorders chapter, since BED and the binge-purge subtype of anorexia show elevated rates of impulsivity and personality disorder diagnoses. The cultural considerations in Criterion B of anorexia tie back to the course's broader discussion of how the DSM-5 handles cross-cultural diagnostic validity.
Eating disorders, anorexia nervosa, bulimia nervosa, binge-eating disorder, BED, DSM-5 eating disorder criteria, restricting type anorexia, binge-purge type anorexia, OSFED, EDNOS, other specified feeding or eating disorder, night eating disorder, atypical anorexia, partial-syndrome eating disorder, amenorrhea, BMI 18.5, body image distortion, compensatory behaviours, purging, diagnostic migration, obesity and mental health, abnormal psychology chapter 12