Anorexia Nervosa

Diagnostic Criteria

According to DSM-5, the key features of anorexia nervosa are:

1. Restriction of energy intake leading to a significantly low body weight (in context of age, sex, developmental trajectory, and physical health).

2. Intense fear of gaining weight or persistent behaviour that interferes with weight gain.

3. Disturbance in the way one’s body weight or shape is experienced, undue influence of body weight or shape on self-evaluation, or lack of recognition of the seriousness of current low body weight.

Subtypes:

• Restrictive Type: Weight loss primarily through dieting, fasting, or excessive exercise.

• Binge-Eating/Purging Type: Regular episodes of binge eating or purging (e.g. self-induced vomiting, misuse of laxatives/diuretics).

Clinical Features

1. Psychological/Behavioural

   • Intense preoccupation with food, weight, calories

   • Fear of weight gain; body-image distortion

   • Restrictive eating patterns, obsessive calorie counting

   • In adolescents: Possible amenorrhoea or delayed menarche

2. Physical

   • Low BMI (often <17.5 kg/m² in adults)

   • Lanugo hair (fine downy hair on body)

   • Cold intolerance, hypothermia

   • Cardiovascular changes: Bradycardia, hypotension, arrhythmias

   • Amenorrhoea or oligomenorrhoea in females; low libido in males

   • Bone density loss (osteopenia/osteoporosis)

   • GI issues: Early satiety, constipation

3. Common Presentations in General Practice

   • Persistent, significant weight loss or failure to gain weight (in adolescents)

   • Excessive exercise routines despite low weight

   • Fatigue, dizziness, fainting episodes (due to hypoglycaemia or low blood pressure)

   • Psychological distress about body shape, weight, and food

Investigations

A thorough medical assessment is essential to evaluate nutritional status, complications, and potential aetiological factors:

1. Routine Blood Tests

   • FBC (Full Blood Count)

   • eLFTs (Electrolytes, Liver Function Tests)

   • CMP (Calcium, Magnesium, Phosphate)

   • FBG (Fasting Blood Glucose)

2. Endocrine & Nutritional Tests

   • Iron studies, B12/folate for anaemia

   • TSH (thyroid disorders)

   • FSH, LH, oestradiol, prolactin (menstrual irregularities, hypogonadism)

3. Cardiac

   • ECG to detect arrhythmias, QT prolongation

4. Bone Health

   • DXA (Bone Densitometry) if prolonged low weight or amenorrhoea >6 months

5. Additional Assessments as indicated (e.g. coeliac serology if malabsorption is suspected)

Management Principles

A multidisciplinary approach is key, involving GP, dietitian, mental health professionals, and sometimes specialist eating disorder services.

1. Nutritional Rehabilitation

   • Goal: Gradual weight restoration, typically 0.5–1.0 kg/week inpatient or 0.25–0.5 kg/week outpatient.

   • Dietitian: Structured meal plans, addressing energy requirements, portion sizes.

2. Psychological Therapies

   • Family-Based Therapy (FBT): First-line in children and adolescents. Focuses on empowering parents to manage the child’s eating and weight restoration.

   • Individual Therapy: Cognitive Behavioural Therapy (CBT-E), Interpersonal Therapy (IPT), or psychodynamic approaches depending on individual needs.

   • Motivational interviewing for engagement if low insight or ambivalence.

3. Monitoring & Medical Support

   • Regular physical exams: Check vital signs, BMI/weight, electrolytes.

   • Refeeding Syndrome: Monitor phosphate, magnesium, potassium closely when reintroducing calories; consider prophylactic supplementation if high risk.

   • Psychiatric comorbidities: Depression, anxiety, OCD traits may require additional treatment (e.g. SSRIs).

4. When to Consider Pharmacotherapy

   • Pharmacological treatment is not a primary intervention for anorexia nervosa, but SSRIs or other medications may help with comorbid depression or anxiety once partial weight restoration is achieved.

Hospital Admission Criteria

Admission is warranted for acute medical risk or severe psychiatric instability. Common thresholds include:

• Severe Hypotension: BP <90 mmHg in adults; <80 mmHg in children

• Bradycardia: HR <40 bpm (adults); <50 bpm (children/adolescents)

• Postural Tachycardia/Hypotension: >20 mmHg drop on standing

• Hypothermia: <36°C, or fever >38°C indicating possible infection

• Hypoglycaemia: BGL <3 mmol/L

• Critically low BMI: <14 kg/m² in adults or rapid weight loss in adolescents

• Electrolyte abnormalities: e.g. severe hypokalaemia, hypophosphataemia

Screening Tool: SCOFF Questionnaire

1. Sick: Do you make yourself sick when you feel uncomfortably full?

2. Control: Do you worry you have lost control over how much you eat?

3. One stone: Have you recently lost more than 6.35 kg (one stone) in a 3-month period?

4. Fat: Do you believe yourself to be fat when others say you are too thin?

5. Food: Would you say that food dominates your life?

Interpretation: Scoring ≥2 suggests a likely eating disorder and warrants further assessment.

Special Populations

1. Adolescents

   • Early intervention can prevent long-term complications (growth and pubertal delay).

   • Family involvement is crucial, especially with FBT.

2. Childbearing Age

   • Infertility and obstetric risks (low birth weight, miscarriages).

   • Advisable to delay pregnancy until stable nutritional status.

3. Postpartum

   • Increased risk of relapse due to stress, sleep deprivation, body image changes.

Complications

1. Medical

   • Osteopenia/osteoporosis: Increased fracture risk.

   • Electrolyte imbalances (e.g. hypokalaemia, hypophosphataemia → arrhythmias, refeeding syndrome).

   • Cardiac: Bradycardia, arrhythmias, risk of sudden death.

   • Amenorrhoea, infertility.

   • GI: Gastroparesis, constipation.

2. Psychiatric

   • Comorbidity: Depression, anxiety disorders, OCD traits.

   • Suicide Risk: Highest among eating disorders; requires vigilant monitoring.

Notes:

• Early detection is critical; consider screening with SCOFF in high-risk individuals (adolescents, underweight patients, females with menstrual irregularities).

• Family-based therapy is first-line in younger patients.

• Monitor refeeding syndrome when increasing caloric intake.

• Multidisciplinary approach: GP, dietitian, psychologist/psychiatrist, and others as needed (endocrinology, cardiology).

• Hospital admission thresholds are based on physiological instability, severe malnutrition, or psychiatric crisis.