Difficulty: Introductory | Prerequisites: None, though a basic grasp of adolescent developmental psychology is helpful.
Tags: eating disorders, anorexia nervosa, bulimia nervosa, binge eating, purging, body image, body dysmorphia, self-induced vomiting, laxative abuse, adolescent psychology, PSY II, abnormal psychology
Eating disorders sit at the intersection of abnormal psychology, developmental psychology and health psychology. They come up in most introductory and intermediate psych courses because they illustrate how biological, psychological and social factors combine to produce disordered behaviour. You do not need specialist clinical knowledge to engage with this material, but you should be comfortable with the idea that mental disorders have multiple contributing causes rather than a single trigger. Understanding anorexia nervosa and bulimia nervosa gives you a foundation for later study of anxiety disorders, obsessive-compulsive spectrum conditions and adolescent mental health.
Anorexia nervosa and bulimia nervosa are the two major eating disorders covered in introductory psychology. Anorexia centres on extreme food restriction driven by an intense fear of weight gain and a distorted body image, while bulimia involves cycles of binge eating followed by compensatory behaviours such as purging or excessive exercise. Both disorders typically emerge during adolescence, can cause serious long-term health damage, and affect the individual's family and social circle, not just the person diagnosed.
Anorexia nervosa
A disorder characterised by an extreme fear of gaining weight, a distorted perception of body shape and size, and persistent behaviour that restricts energy intake, leading to significantly low body weight.
In simple terms, this means the person sees themselves as overweight even when they are dangerously thin, and they go to great lengths to eat as little as possible.
Bulimia nervosa
A disorder characterised by recurrent episodes of binge eating followed by compensatory ("purging") behaviours intended to prevent weight gain, such as self-induced vomiting, laxative use or compulsive exercise.
Think of it as a cycle: the person eats a large amount of food in a short period, then tries to undo it through purging or extreme exercise.
Binge eating
Consuming an unusually large quantity of food in a discrete period, typically accompanied by a feeling of loss of control.
In simple terms, this means eating far more than most people would eat in the same situation, while feeling unable to stop.
Purging behaviours
Actions taken after eating to eliminate food from the body or counteract caloric intake. Common methods include self-induced vomiting, misuse of laxatives or diuretics, and compulsive exercise.
Think of it as the "undoing" step in the binge-purge cycle.
Body image distortion
A persistent misperception of one's own body shape or size that does not align with objective reality.
In simple terms, the person genuinely believes their body looks different from how others see it, often perceiving themselves as larger than they are.
Compensatory behaviours
Any behaviour used to offset perceived caloric intake. This is a broader term than purging and can include fasting, excessive exercise and restriction of subsequent meals.
Think of it as any strategy, healthy or unhealthy, used to "make up for" eating.
Individuals have an extreme, persistent fear of gaining weight
Body image is distorted: they perceive themselves as overweight even at dangerously low body weight
Food restriction methods include:
Severe dieting or fasting
Excessive physical exercise
Obsessive calorie counting and food monitoring
People with anorexia strive to maintain a very low weight and are often visibly thin or underweight
The disorder interferes with daily life and can cause permanent health damage
Defined by habitual binge eating followed by food elimination (purging) behaviours
Purging methods include:
Self-induced vomiting
Laxative or diuretic misuse
Compulsive physical exercise
People with bulimia may experience significant weight fluctuations but rarely reach the very low weight seen in anorexia
Body weight is often normal or even above average, which can make the disorder less visible to others
Both disorders involve an unhealthy preoccupation with food, weight and body shape
Both can involve compulsive exercise and other compensatory behaviours
The key difference in presentation is body weight: anorexia typically produces noticeable underweight, while bulimia does not
Both disorders can co-occur with other psychological conditions and cause lasting physiological harm
Eating disorders most commonly emerge during adolescence, a period of major body changes and heightened social pressure around appearance
Concern about physical appearance is normal in children and adolescents, but in a growing proportion this concern becomes an obsession that crosses into clinical territory
The disorders affect not just the individual but also the family unit and wider social group
Parents and caregivers can reduce risk by promoting self-esteem and healthy attitudes toward food and physical appearance
Early identification and intervention improve outcomes
If an eating disorder is suspected, seeking appropriate medical attention is important rather than waiting for the behaviour to resolve on its own
School counsellors, paediatricians and parents use knowledge of eating disorder warning signs to intervene before the condition becomes entrenched. Recognising that a teenager's "healthy eating" has tipped into obsessive restriction, or that frequent bathroom visits after meals may indicate purging, can prompt early referral and significantly improve long-term outcomes. Public health campaigns targeting adolescent body image (for example, media literacy programmes in schools) draw directly on the psychological models covered here.
Students often think anorexia and bulimia are the same disorder. They are not. While they share features (preoccupation with weight, potential for compulsive exercise), anorexia is primarily about restriction and bulimia is primarily about the binge-purge cycle.
Students often assume that someone with bulimia must be underweight. In fact, people with bulimia are frequently at a normal weight or above, which is one reason the disorder can go undetected.
Students sometimes believe eating disorders are a choice or a matter of willpower. They are clinically recognised mental disorders with biological, psychological and social components.
Students may think eating disorders only affect teenage girls. While adolescent females are at highest risk, eating disorders occur across all ages, genders and demographics.
⚠️ Know the distinguishing features of anorexia vs. bulimia. Exam questions frequently present a scenario and ask you to identify which disorder fits. The body-weight difference is the most reliable distinguishing cue in a short vignette.
⚠️ Be able to list compensatory behaviours common to both disorders (vomiting, laxative use, excessive exercise) and those more associated with one than the other (severe food restriction is more characteristic of anorexia; binge-purge cycling is more characteristic of bulimia).
⚠️ Understand that eating disorders have a biopsychosocial aetiology. Questions may ask you to identify biological, psychological and social contributing factors.
⚠️ Know the role of early intervention and the importance of parental and family involvement in prevention and treatment.
True or false: People with bulimia nervosa are always underweight. (False. They are often normal weight or above.)
Fill in the blank: Anorexia nervosa is characterised by an extreme fear of ______ and a distorted ______. (gaining weight; body image)
True or false: Both anorexia and bulimia can involve compulsive exercise as a compensatory behaviour. (True.)
Fill in the blank: The binge-purge cycle is the defining pattern of ______ nervosa. (bulimia)
True or false: Eating disorders are purely psychological and have no biological component. (False. They have biological, psychological and social contributing factors.)
Q: A 16-year-old patient has a BMI significantly below the healthy range, reports intense anxiety about gaining weight, and perceives herself as overweight despite being visibly underweight. Which eating disorder is most consistent with this presentation?
A: Anorexia nervosa. The combination of significantly low body weight, fear of weight gain and body image distortion is characteristic of anorexia.
Q: Describe two compensatory behaviours that are common in bulimia nervosa.
A: Self-induced vomiting and misuse of laxatives. Compulsive exercise is also a common compensatory behaviour in bulimia.
Q: What is the most reliable clinical feature for distinguishing anorexia nervosa from bulimia nervosa?
A: Body weight. Individuals with anorexia are typically significantly underweight, while those with bulimia are usually at a normal weight or above.
Q: Explain why eating disorders are described as having a biopsychosocial aetiology.
A: They arise from a combination of biological factors (genetics, neurochemistry), psychological factors (low self-esteem, body image distortion, anxiety) and social factors (peer pressure, media influence, cultural ideals around body shape). No single cause is sufficient on its own.
Q: A parent asks how they can help prevent their adolescent from developing an eating disorder. Based on the material, what two strategies would you recommend?
A: Promoting healthy self-esteem and fostering positive attitudes toward food and physical appearance. If warning signs appear, seeking early medical attention rather than waiting is also important.
This material connects to anxiety disorders because the fear of weight gain in anorexia shares features with phobic anxiety, and obsessive calorie-counting resembles obsessive-compulsive patterns. It also links to adolescent developmental psychology, since the onset of eating disorders typically coincides with puberty and the identity formation that accompanies it. If your course covers the biopsychosocial model of mental illness more broadly, eating disorders serve as a clear worked example of that framework in action.
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