Eating disorders are complex conditions that disrupt normal eating patterns and severely impact physical and mental health. They involve a range of behaviors from extreme food restriction to binge eating, often driven by distorted body image and intense fear of weight gain.
Understanding the physiological basis of eating disorders is crucial. These conditions involve disruptions in neuroendocrine systems, brain circuitry, and metabolism. Genetic factors, environmental influences, and individual traits all play roles in their development and maintenance.
Eating Disorder Types and Criteria
Anorexia and Bulimia
- Anorexia Nervosa involves severe food intake restriction, intense fear of weight gain, and distorted body image
- Diagnostic criteria include significantly low body weight and persistent behaviors interfering with weight gain
- Subtypes include restrictive and binge-eating/purging
- Bulimia Nervosa characterized by recurrent binge eating episodes followed by compensatory behaviors
- Compensatory behaviors include self-induced vomiting, laxative misuse, and excessive exercise
- Diagnostic criteria require binge-purge cycles at least once per week for 3 months
Binge Eating and Other Specified Disorders
- Binge Eating Disorder defined by recurrent episodes of consuming large amounts of food rapidly
- Accompanied by loss of control and marked distress
- Diagnostic criteria require binge episodes at least once per week for 3 months
- Other Specified Feeding or Eating Disorders (OSFED) include atypical presentations causing significant distress
- Examples include atypical anorexia nervosa (normal weight) and subthreshold bulimia nervosa
- Avoidant/Restrictive Food Intake Disorder (ARFID) involves highly selective eating unrelated to body image
- Characterized by persistent failure to meet nutritional needs due to sensory aversions or fear of adverse consequences
Less Common Eating Disorders
- Pica involves persistent consumption of non-food substances for at least one month
- Substances consumed may include clay, dirt, paper, or ice
- Must be developmentally inappropriate and not part of culturally supported practice
- Rumination Disorder defined by repeated regurgitation of food for at least one month
- Regurgitated food may be re-chewed, re-swallowed, or spit out
- Not due to an associated gastrointestinal condition or other medical disorder
Eating Disorder Physiology and Neurobiology
Neuroendocrine Disruptions
- Hypothalamic-pituitary-adrenal (HPA) axis disruptions lead to altered stress responses and hormonal imbalances
- Elevated cortisol levels observed in anorexia nervosa
- Blunted cortisol response to stress in bulimia nervosa
- Dysregulation of appetite-regulating neuropeptides contributes to abnormal eating patterns
- Leptin levels decreased in anorexia nervosa, affecting satiety signals
- Ghrelin levels increased in anorexia nervosa, potentially driving food preoccupation
- Neuropeptide Y alterations influence food intake and energy balance
Neurotransmitter and Brain Changes
- Serotonin and dopamine systems show alterations affecting mood regulation and reward processing
- Reduced serotonin activity in anorexia nervosa linked to anxiety and obsessionality
- Altered dopamine function in bulimia nervosa associated with impulsivity and reward sensitivity
- Neuroimaging studies reveal structural and functional brain changes in eating disorder patients
- Reduced gray matter volume in regions associated with appetite regulation (hypothalamus, insula)
- Altered activation patterns in reward circuits during food-related tasks
- Abnormal activity in parietal cortex regions involved in body image perception
- Metabolic adaptations occur in response to prolonged food restriction or binge-purge cycles
- Decreased resting metabolic rate in anorexia nervosa as an energy-conserving mechanism
- Altered thermoregulation and reduced brown adipose tissue activity
- Gut microbiota composition and function changes observed in eating disorders
- Reduced microbial diversity in anorexia nervosa
- Alterations in short-chain fatty acid production affecting mood and appetite regulation
- Cognitive processing biases related to food, weight, and body shape influence perception
- Attentional bias towards food-related stimuli in binge eating disorder
- Overestimation of body size in anorexia nervosa due to perceptual distortions
Genetics and Environment in Eating Disorders
Genetic Factors
- Twin and family studies demonstrate significant genetic component in eating disorder heritability
- Heritability estimates range from 40% to 60% for anorexia nervosa
- Concordance rates higher in monozygotic twins compared to dizygotic twins
- Specific gene variants implicated in eating disorder susceptibility
- Serotonin transporter gene (SLC6A4) polymorphisms associated with anorexia nervosa
- Brain-derived neurotrophic factor (BDNF) gene variations linked to bulimia nervosa
- Epigenetic modifications alter gene expression related to stress response and appetite regulation
- DNA methylation changes in genes involved in stress reactivity (FKBP5) observed in anorexia nervosa
- Histone modifications affecting appetite-regulating genes (POMC) found in binge eating disorder
Environmental Risk Factors
- Sociocultural factors contribute to body dissatisfaction and disordered eating behaviors
- Media influence promoting unrealistic beauty standards
- Cultural ideals of thinness vary across different societies
- Adverse childhood experiences increase risk of developing eating disorders
- Sexual abuse associated with increased risk of bulimia nervosa
- Emotional neglect linked to higher likelihood of anorexia nervosa
- Family dynamics shape eating behaviors and disorder risk
- Parental criticism of weight or shape increases eating disorder vulnerability
- Family meals and positive food-related interactions serve as protective factors
Individual Characteristics
- Personality traits associated with higher likelihood of developing eating disorders
- Perfectionism commonly observed in individuals with anorexia nervosa
- Impulsivity more prevalent in those with bulimia nervosa and binge eating disorder
- Cognitive factors contribute to eating disorder development and maintenance
- Rigid thinking patterns and cognitive inflexibility in anorexia nervosa
- Negative self-evaluation and body image disturbance across eating disorders
Health Consequences and Treatment of Eating Disorders
Medical Complications
- Cardiovascular system affected by malnutrition and electrolyte imbalances
- Bradycardia and orthostatic hypotension common in anorexia nervosa
- Arrhythmias risk increased due to electrolyte disturbances in purging disorders
- Gastrointestinal complications arise from disordered eating behaviors
- Delayed gastric emptying and constipation in restrictive eating disorders
- Dental erosion and esophageal damage from frequent purging in bulimia nervosa
- Endocrine system disruptions impact hormonal balance and fertility
- Hypothalamic amenorrhea in females with anorexia nervosa
- Reduced bone mineral density increasing fracture risk
Psychological and Cognitive Impact
- Mood disorders frequently co-occur with eating disorders
- Major depressive disorder commonly comorbid with anorexia nervosa
- Anxiety disorders, particularly social anxiety, prevalent in eating disorder populations
- Cognitive impairments observed in individuals with severe eating disorders
- Difficulties with attention and working memory in acute anorexia nervosa
- Decision-making deficits persist even after weight restoration
Treatment Approaches
- Enhanced cognitive behavioral therapy (CBT-E) considered gold standard for bulimia nervosa and binge eating disorder
- Focuses on modifying dysfunctional thoughts and behaviors related to eating, weight, and shape
- Typically delivered in 20-40 individual sessions
- Family-based treatment (FBT) first-line approach for adolescents with anorexia nervosa
- Emphasizes parental involvement in managing eating and weight restoration
- Usually consists of three phases over 6-12 months
- Pharmacological interventions used as adjunctive treatments
- Selective serotonin reuptake inhibitors (SSRIs) (fluoxetine) effective for bulimia nervosa
- Lisdexamfetamine approved for moderate to severe binge eating disorder
- Nutritional rehabilitation crucial component of treatment, especially for anorexia nervosa
- Gradual refeeding to avoid refeeding syndrome
- Structured meal plans and nutritional counseling to normalize eating patterns
- Multidisciplinary treatment teams address complex nature of eating disorders
- Psychiatrists manage medication and comorbid mental health conditions
- Psychologists provide psychotherapy and cognitive-behavioral interventions
- Dietitians develop individualized meal plans and address nutritional deficiencies
- Medical doctors monitor and treat physical health complications