Eating Disorders Overview and Anorexia Nervosa

Eating Disorders: Overview

• This lecture focuses on anorexia nervosa (AN) and bulimia nervosa (BN).
• Other eating disorders include: other specified feeding or eating disorders (OSFED), binge eating disorder (BED), and night eating disorder.
• OSFED is a category for those who don't meet AN or BN criteria, but show characteristics of one or both.
• BED is characterized by repeated overeating without compensatory behaviors, and is common in obese individuals (9-18% of obese).
• Night eating disorder is linked to obesity and abnormal circadian rhythm potentially linked to leptin dysfunction.
• Rumination disorder involves repeated regurgitation and rechewing.
• Avoidant/restrictive food intake disorder is similar to anorexia, but without fear of weight gain.

Anorexia Nervosa (AN): Clinical Definition

• Restriction of energy intake, leading to significantly low body weight (determined by BMI relative to age, gender, and health expectations).
• Intense fear of gaining weight or becoming fat, or persistent behaviors interfering with weight gain (even at low weight).
• Disturbance of perception of shape or body weight, and denial of the seriousness of current low body weight.
• Subtypes: Restricting (dieting, fasting, exercise) and binge-eating/purging (vomiting, laxatives, diuretics, enemas).

Anorexia Nervosa (AN): Prevalence

• Lifetime prevalence of AN is 0.5-2% in women.
• Predominantly affects women in middle to upper middle class Caucasian.
• Higher rates in those involved in dance, fashion, and elite sports.
• Typically appears around 12-13 years (post-menarche).

Anorexia Nervosa (AN): Onset

• Starts with minor dietary changes, abandoning desserts, then meats, then fat-containing foods.
• Vegetarianism or "safe-foods" (like lettuce and fruit) are sometimes used to justify, with decreased eating speed and longer intervals between meals.

Anorexia Nervosa (AN): Medical Consequences

• Overactivity and cold sensitivity.
• Multiple endocrine abnormalities (e.g., type 1 diabetes).
• Low blood pressure, slow heart rate.
• Diminished libido, amenorrhea (absence of menstruation).
• Osteoporosis (post-recovery).
• Neuropsychological impairments in learning and memory.
• Anxiety and depression.
• Estimated lifetime mortality rate of 5-10%.

Anorexia Nervosa (AN): Cause

• Earliest documentation is in the 15th-16th centuries.
• No single cause identified.
• Multiple interacting factors include genetics, biological, psychological, and social/cultural factors.

Anorexia Nervosa (AN): Genetics

• Significant genetic component; female relatives 7-20x more likely to develop AN.
• Monozygotic (MZ) twins show higher concordance for AN than dizygotic (DZ) twins.
• Estimates suggest 58-76% of variance in AN is due to genetics.
• Related to certain personality traits (e.g., perfectionism, inflexibility, and restraint), abnormality in serotonin metabolism, and chronic anxiety.

Anorexia Nervosa (AN): Developmental Factors

• 25% of AN parents have a history of obstetric difficulty or loss.
• Higher incidence of prematurity and birth trauma in AN children.
• Parents of AN children report higher anxiety during pregnancy.
• Parents often controlling and overprotective.
• Abnormal attachment styles (e.g., dismissive, insecure) in AN parents.

Anorexia Nervosa (AN): HPA Axis

• The HPA axis is composed of hypothalamus, pituitary, and adrenal glands, involved in stress response.
• Stress chronically high cortisol leads to muscle wasting, high glucose, immune suppression, and hippocampal damage.
• AN shows abnormal HPA function and multiple biological causes.
• Profound changes during puberty potentially increase vulnerability.

Anorexia Nervosa (AN): Causal Synthesis

• Predisposing factors include abnormal HPA, increased serotonin, anxiety enhanced satiety, biological window, situational factors, chronic stress.
• Results in manifestation of AN.

Anorexia Nervosa (AN): Maintenance

• Weight loss initially is satisfying, but increasingly punitive measures are implemented.
• Highly stylized eating rituals develop including food types becoming restricted.
• Social avoidance increases
• Pursuit of weight loss becomes the sole goal.
• Biological factors suggest potential addiction of weight loss.

Anorexia Nervosa (AN): Prognosis & Treatment

• 50% achieve full recovery.
• 30% experience occasional relapse.
• 20% exhibit chronic AN.
• Treatment combines CBT (cognitive behavioral therapy) and antidepressants.
• CBT helps with identifying triggers for bingeing and coping mechanisms.
• Antidepressants may be effective after refeeding to prevent relapse.

Bulimia Nervosa (BN): Clinical Definition

• Recurrent episodes of binge eating (large amounts of food in a discrete period with lack of control).
• Inappropriate compensatory behaviors (vomiting, laxatives, excessive exercise) to avoid weight gain.
• Binge eating and compensation occur at least once a week for 3 months, and self-evaluation is heavily influenced by body weight and shape.

Bulimia Nervosa (BN): Prevalence and Medical Consequences

• Lifetime prevalence is ~1-3% in women.
• Typically appears in late adolescence/early adulthood.
• Benign relative to AN, but can include dental erosion, parotid gland swelling ("chipmunk face") electrolyte imbalances, and complications like esophageal tears.

Bulimia Nervosa (BN): Cause

• History of AN may be a factor in some cases.
• Potential predisposition may include dieting, childhood/parental obesity, family environment, critical comments about weight, sexual abuse, anxiety and depression.

Bulimia Nervosa (BN): Instigation and Maintenance

• A plausible model of BN onset involves dieting, preoccupation with weight, quick weight loss methods, perceived control over food/purging.
• Frequency/duration of binges and triggers generally increases.
• Physiologic changes related to abnormal satiety are observed, including enlarged gastric capacity, delayed emptying, diminished elasticity of the stomach, impaired CCK release (diminished post-meal satiety), and abnormal serotonergic function.

Bulimia Nervosa (BN): Prognosis & Treatment

• Treatment response varies but a successful outcome is achievable.
• CBT and antidepressants often provide good results.

General Conclusion

• AN and BN are common and complex eating disorders.
• Causation is not fully understood but a range of factors and interactions play a role in their onset.
• BN is generally easier to treat than AN.