6. Eating Disorders

Learning Objectives

By the end of this topic, you should be able to:

• Define eating disorders and identify the core psychological feature shared across them
• Distinguish Anorexia Nervosa, Bulimia Nervosa, and Binge Eating Disorder using DSM-5 diagnostic criteria
• Explain the psychological, biological, and sociocultural factors that contribute to eating disorders
• Describe the major physical health consequences associated with disordered eating
• Describe evidence-based treatment approaches, including family-based therapy and CBT-E
• Apply diagnostic criteria to a case scenario to identify the likely eating disorder

Quick Answer

Eating disorders are psychological disorders involving a persistent disturbance of eating behaviour and related thoughts and emotions, causing significant physical or psychosocial impairment. The three most diagnosed conditions are Anorexia Nervosa (restriction of intake leading to significantly low body weight, intense fear of weight gain, and body image disturbance), Bulimia Nervosa (recurrent binge eating followed by compensatory behaviours like purging, with normal or above-normal body weight), and Binge Eating Disorder (recurrent binge eating without regular compensatory behaviour). They arise from a mix of psychological factors (perfectionism, low self-esteem, body dissatisfaction), biological vulnerability, and sociocultural pressure around appearance, and they carry serious physical health risks — Anorexia Nervosa has one of the highest mortality rates of any psychological disorder. Effective treatment typically combines nutritional rehabilitation, psychotherapy, and medical monitoring.

What Ties Eating Disorders Together?

Despite differing behaviours, eating disorders share a common psychological core: an overvaluation of body shape, weight, or control over eating, which becomes central to the person's self-worth. This distinguishes disordered eating from ordinary dieting or health-conscious eating — the defining feature is not the specific food behaviour itself but the degree to which weight and shape dominate a person's thinking and self-evaluation, alongside significant functional or physical impairment.

Anorexia Nervosa

Anorexia Nervosa involves three core features:

• Restriction of energy intake relative to requirements, leading to a significantly low body weight in the context of age, sex, developmental trajectory, and physical health
• Intense fear of gaining weight or becoming fat, or persistent behaviour that interferes with weight gain, even at a significantly low weight
• Disturbance in self-perceived body weight or shape, undue influence of body weight/shape on self-evaluation, or persistent lack of recognition of the seriousness of the current low body weight

DSM-5 recognises two subtypes: restricting type (weight loss achieved primarily through dieting, fasting, or excessive exercise) and binge-eating/purging type (recurrent episodes of binge eating or purging behaviour, such as self-induced vomiting or laxative misuse, during the current episode).

Why it matters: Anorexia Nervosa has one of the highest mortality rates among psychological disorders, from both medical complications of starvation and elevated suicide risk, making early identification and intervention critical.

Common misunderstanding: Anorexia is often assumed to always involve visibly extreme thinness, but a person at a "normal" weight who has lost a significant amount of weight, shows the psychological features (intense fear of weight gain, body image disturbance), and has stopped menstruating or shows other physiological signs of malnutrition can still meet criteria — DSM-5 removed the previous strict amenorrhea requirement precisely because presentation varies.

Bulimia Nervosa

Bulimia Nervosa is characterised by:

• Recurrent episodes of binge eating — eating, within a discrete period, an amount of food definitely larger than most people would eat under similar circumstances, accompanied by a sense of lack of control over eating
• Recurrent inappropriate compensatory behaviours to prevent weight gain — self-induced vomiting, misuse of laxatives/diuretics, fasting, or excessive exercise
• Both behaviours occurring, on average, at least once a week for three months
• Self-evaluation unduly influenced by body shape and weight
• The disturbance does not occur exclusively during episodes of Anorexia Nervosa

Real-world example: A person maintains a body weight within the typical range but privately consumes very large amounts of food in short bursts several times a week, feeling unable to stop once starting, and then induces vomiting out of shame and fear of weight gain. Because body weight often appears unremarkable, Bulimia Nervosa can go unnoticed far longer than Anorexia Nervosa, despite carrying its own serious health risks — particularly electrolyte imbalances from purging, which can cause life-threatening cardiac complications.

Binge Eating Disorder

Binge Eating Disorder involves recurrent binge eating episodes (as defined above) occurring at least once a week for three months, associated with marked distress, and at least three of: eating much more rapidly than normal, eating until uncomfortably full, eating large amounts when not physically hungry, eating alone due to embarrassment, or feeling disgusted/depressed/guilty afterward — without the regular compensatory behaviours seen in Bulimia Nervosa.

Why it matters: Binge Eating Disorder is actually the most common eating disorder in many populations, yet it receives less public attention than Anorexia or Bulimia, partly because it is not defined by dramatic weight loss or purging behaviour and can be mistaken for a lack of willpower rather than a recognised psychological disorder requiring treatment.

Psychological, Biological, and Sociocultural Factors

Eating disorders develop through an interaction of multiple contributing factors, not a single cause:

• Psychological factors — perfectionism, low self-esteem, difficulty tolerating negative emotions, and a need for control (particularly prominent in Anorexia Nervosa)
• Biological factors — genetic predisposition (eating disorders run in families and show notable heritability in twin studies), and neurochemical factors affecting appetite regulation and reward processing
• Sociocultural pressures — internalisation of narrow beauty ideals, media and social media exposure, weight-based teasing, and participation in appearance- or weight-focused activities (e.g., certain sports, modelling) are documented risk factors
• Trauma and adverse experiences — a history of trauma, including childhood abuse, is associated with elevated risk across eating disorder types

Why it matters: Because multiple factors interact, effective prevention and treatment must go beyond simplistic messages about food and willpower, addressing underlying emotional regulation, self-esteem, and cultural pressures.

Physical Health Implications

Eating disorders carry serious, sometimes life-threatening physical consequences:

• Malnutrition — affects nearly every organ system, particularly in Anorexia Nervosa
• Cardiovascular problems — bradycardia (dangerously slow heart rate) and arrhythmias, especially from electrolyte imbalances caused by purging
• Electrolyte imbalances — low potassium (hypokalemia) from vomiting or laxative misuse can be life-threatening
• Gastrointestinal issues — from binge eating, purging, and chronic restriction
• Reproductive and bone health issues — menstrual irregularities and osteoporosis from prolonged malnutrition and hormonal disruption
• Dental erosion — from repeated exposure to stomach acid during self-induced vomiting

Diagnosis and Assessment

A comprehensive evaluation combines several sources of information:

• Clinical interviews exploring eating patterns, body image, and psychological history
• Medical examination to assess weight, vital signs, and physical complications
• Standardised tools — the Eating Disorder Inventory (EDI) provides a detailed profile of eating disorder symptoms and related psychological features; the brief SCOFF questionnaire (Sick, Control, One stone, Fat, Food) is a widely used screening tool in primary care
• Laboratory tests — to check for electrolyte imbalances and other medical complications

Treatment Approaches

Treatment is typically delivered by a multidisciplinary team, combining medical, nutritional, and psychological care:

• Family-Based Therapy (FBT) — particularly effective for adolescents with Anorexia Nervosa, empowering parents to take an active role in restoring their child's weight and eating behaviour before gradually returning control to the adolescent
• Cognitive-Behavioural Therapy, Enhanced (CBT-E) — the leading evidence-based psychotherapy for Bulimia Nervosa and Binge Eating Disorder, targeting the overvaluation of shape/weight and disrupting the binge-purge or binge cycle
• Nutritional counselling — restoring regular, adequate eating patterns and correcting nutritional deficits
• Medication — antidepressants (particularly SSRIs) have evidence for reducing binge-purge frequency in Bulimia Nervosa and can help with co-occurring depression or anxiety; medication has more limited standalone evidence in Anorexia Nervosa
• Medical monitoring — essential throughout treatment, especially for Anorexia Nervosa, given the risk of cardiac complications during both illness and the refeeding process

Why it matters: No single treatment fits every eating disorder or every patient — treatment intensity ranges from outpatient therapy to inpatient medical stabilisation depending on severity, and coordination between medical and mental health providers is essential given the physical risks involved.

Prevention

Prevention efforts focus on reducing known risk factors before disordered eating develops:

• Promoting body image resilience and media literacy, particularly around social media
• Reducing weight-based teasing and stigma in schools and families
• Encouraging balanced, non-restrictive relationships with food rather than dieting culture
• Early screening and support for individuals showing early warning signs (e.g., preoccupation with weight, skipping meals, secretive eating)

Key Terms

Term	Definition	Related Concept
Anorexia Nervosa	Restriction of intake leading to significantly low body weight, fear of weight gain, and body image disturbance	Restricting type, binge-eating/purging type
Bulimia Nervosa	Recurrent binge eating with compensatory behaviours, at least weekly for 3 months, normal/above-normal weight	Purging, self-evaluation tied to shape/weight
Binge Eating Disorder	Recurrent binge eating without regular compensatory behaviour, at least weekly for 3 months	Bulimia Nervosa (contrast)
Binge eating episode	Eating an unusually large amount of food with a sense of loss of control	Bulimia Nervosa, Binge Eating Disorder
Compensatory behaviour	Behaviour intended to prevent weight gain after eating, e.g., purging, laxative misuse, excessive exercise	Bulimia Nervosa
CBT-E	Enhanced cognitive-behavioural therapy targeting overvaluation of shape/weight; leading treatment for BN and BED	Treatment approaches
Family-Based Therapy (FBT)	A treatment empowering parents to lead weight restoration in adolescents with Anorexia Nervosa	Treatment approaches
SCOFF questionnaire	A brief 5-item screening tool for eating disorders used in primary care	Diagnosis and assessment

Common Mistakes

Misconception: Someone must look extremely underweight to have an eating disorder.

Why it's wrong: Bulimia Nervosa and Binge Eating Disorder typically occur at normal or above-normal body weight, and even Anorexia Nervosa can present at a range of weights depending on a person's starting point and degree of weight loss. Focusing only on visible thinness causes many cases to go unrecognised.

Correct understanding: Diagnosis depends on behavioural and psychological criteria (binge/purge patterns, fear of weight gain, overvaluation of shape/weight), not solely on visible body size.

---

Misconception: Eating disorders are a lifestyle choice or a result of vanity.

Why it's wrong: Eating disorders are recognised psychological disorders shaped by genetic predisposition, neurobiology, psychological factors like perfectionism and emotion regulation difficulties, and sociocultural pressure — not a simple choice or superficial concern about appearance.

Correct understanding: Eating disorders are complex, multi-factorial psychological conditions requiring clinical treatment, not a matter of willpower or vanity.

---

Misconception: Binge Eating Disorder is just "overeating" and not a real clinical disorder.

Why it's wrong: BED involves a distinct pattern of loss-of-control eating occurring at least weekly for three months, marked distress, and specific associated features (eating rapidly, eating past fullness, eating alone from embarrassment) — meeting a defined diagnostic threshold, unlike occasional overeating.

Correct understanding: Binge Eating Disorder is a recognised DSM-5 diagnosis, and in fact the most common eating disorder in many populations, requiring evidence-based treatment such as CBT-E.

Comparison and Connections

Feature	Anorexia Nervosa	Bulimia Nervosa	Binge Eating Disorder
Body weight	Significantly low	Normal or above-normal	Normal or above-normal
Core behaviour	Restriction of intake	Binge eating + compensatory behaviour	Binge eating, no regular compensation
Frequency criterion	N/A (defined by weight + fear + body image)	Weekly for 3+ months	Weekly for 3+ months
Primary physical risk	Starvation-related organ damage, highest mortality	Electrolyte imbalance from purging	Obesity-related complications, metabolic risk
Leading treatment	Family-Based Therapy (adolescents), medical stabilisation	CBT-E	CBT-E

Practice Questions

Recall

1. State the three core diagnostic features of Anorexia Nervosa. Guidance: Restriction of intake leading to significantly low body weight; intense fear of weight gain; disturbance in self-perceived body weight/shape or undue influence of shape/weight on self-evaluation.

2. Name two standardised tools used to assess or screen for eating disorders. Guidance: Eating Disorder Inventory (EDI), SCOFF questionnaire.

Understanding

3. Explain why Bulimia Nervosa can go undetected longer than Anorexia Nervosa. Guidance: Bulimia typically occurs at normal or above-normal body weight, so there is no dramatic visible weight loss to alert others, and binge-purge behaviour is often hidden due to shame.

4. Explain the key behavioural difference between Bulimia Nervosa and Binge Eating Disorder. Guidance: Bulimia Nervosa includes recurrent compensatory behaviours (purging, laxatives, excessive exercise) after binges; Binge Eating Disorder does not involve regular compensatory behaviour.

Application

5. A 16-year-old has lost 20% of her body weight over several months through severe caloric restriction, expresses intense fear of "getting fat" even though she is now underweight, and insists she still looks overweight. Identify the likely diagnosis and a recommended first-line treatment. Guidance: Anorexia Nervosa (restricting type) — Family-Based Therapy is a recommended first-line treatment for adolescents.

6. A client at a normal body weight reports eating very large amounts of food in under an hour several times a week, feeling out of control during these episodes, and inducing vomiting afterward due to shame. Identify the likely diagnosis. Guidance: Bulimia Nervosa — recurrent binge eating plus compensatory purging at least weekly, with self-evaluation influenced by shape/weight.

Analysis

7. Compare the physical health risks most associated with Anorexia Nervosa versus Bulimia Nervosa, and explain why each requires specific medical monitoring. Guidance: Anorexia risks starvation-related organ damage and has the highest mortality of any psychological disorder, requiring monitoring for cardiac complications especially during refeeding; Bulimia risks electrolyte imbalance from purging, which can cause dangerous cardiac arrhythmias even at normal body weight.

8. Evaluate why treatment for eating disorders typically requires a multidisciplinary team rather than psychotherapy alone. Guidance: Eating disorders involve serious physical health risks (cardiac, electrolyte, nutritional) alongside psychological factors, so effective treatment needs coordinated medical monitoring, nutritional rehabilitation, and psychotherapy (e.g., FBT, CBT-E) working together rather than any single intervention in isolation.

FAQ

Can men develop eating disorders, or is it only a concern for women? Men can and do develop eating disorders, though they are diagnosed less frequently, partly due to underrecognition and different presentation (e.g., a stronger focus on muscularity rather than thinness in some cases, sometimes called "muscle dysmorphia"). Eating disorders affect people across genders, ages, and body types, and assuming they only affect women contributes to underdiagnosis in men.

Is dieting the same as having an eating disorder? No. Ordinary dieting for health or personal goals does not typically involve the overvaluation of shape/weight as central to self-worth, the loss of control seen in binge eating, or the significant psychological and physical impairment required for a diagnosis. The distinction lies in the degree of preoccupation, distress, and functional impact, not the act of monitoring food intake itself.

Why did DSM-5 remove the amenorrhea (missed periods) requirement from Anorexia Nervosa criteria? The amenorrhea criterion excluded people who met all other criteria for Anorexia Nervosa but did not lose their periods — including some at lower weights, males, and people on hormonal contraception. Removing it allowed for more accurate and inclusive diagnosis based on the core behavioural and psychological features rather than a single physiological marker that did not apply to everyone.

Can someone recover fully from an eating disorder? Yes, many people achieve full and lasting recovery, particularly with early intervention — adolescents treated with Family-Based Therapy for Anorexia Nervosa show especially strong recovery rates. Recovery can take time and may involve setbacks, but with appropriate multidisciplinary treatment, long-term remission is a realistic outcome for many patients.

Are eating disorders caused by social media and unrealistic body standards? Sociocultural pressure, including media and social media exposure to narrow beauty ideals, is a well-documented risk factor that can trigger or worsen eating disorders, but it is not the sole cause. Eating disorders develop through an interaction of genetic vulnerability, individual psychological factors, and sociocultural pressure — media exposure is a significant contributing factor rather than a single explanation.

Quick Revision

• Eating disorders share a common core: overvaluation of body shape/weight/eating control in self-worth, causing real impairment
• Anorexia Nervosa: significantly low body weight, intense fear of weight gain, body image disturbance; restricting or binge-eating/purging subtype
• Bulimia Nervosa: binge eating + compensatory behaviour, weekly for 3+ months, typically normal/above-normal weight
• Binge Eating Disorder: recurrent binge eating without regular compensatory behaviour, weekly for 3+ months
• DSM-5 removed the amenorrhea requirement from Anorexia Nervosa to allow more inclusive diagnosis
• Anorexia Nervosa has one of the highest mortality rates of any psychological disorder
• Bulimia's main physical danger is electrolyte imbalance from purging, which can cause cardiac arrhythmia
• Binge Eating Disorder is the most common eating disorder in many populations despite less public attention
• Causes involve genetics, psychological factors (perfectionism, low self-esteem), and sociocultural pressure — not willpower or vanity
• Family-Based Therapy is first-line for adolescent Anorexia Nervosa; CBT-E is first-line for Bulimia Nervosa and Binge Eating Disorder
• Treatment requires a multidisciplinary team due to serious physical health risks

Related Topics

Prerequisites Introduction to Psychological Disorders, Mood Disorders

Related Topics Anxiety Disorders, Personality Disorders, Health Psychology, Treatment and Therapy

Next Topics Treatment and Therapy, Psychological Assessment