Anorexia nervosa

• Anorexia nervosa is an eating disorder in which a person persistently restricts energy intake, is intensely afraid of gaining weight, and experiences body image as disturbed, usually with clinically significant underweight.
• It is the most lethal of the psychiatric illnesses, both through the medical consequences of starvation and through suicide.
• The goal of treatment is weight restoration combined with psychological therapy; medication alone does not treat anorexia nervosa.
• Medical complications affect nearly every body system, but most are reversible with nutritional rehabilitation.
• Early identification, specialist referral and family involvement, especially for adolescents, improve the outlook.

By the end of this page you can:

1. State the diagnostic criteria for anorexia nervosa and distinguish the restricting and binge-eating/purging subtypes.
2. Recognise the presentation and key physical signs of anorexia nervosa and interpret appropriate investigations.
3. Apply MEED and NICE criteria to decide when a patient needs urgent assessment or admission.
4. Outline evidence-based psychological and nutritional treatment and the rationale for each.
5. Explain refeeding syndrome, how it is prevented and how it is treated.
6. Describe the main medical complications and the prognosis.

The definition above is paraphrased from DSM-5-TR, and the word "anorexia" is from the Greek for loss of appetite. Patients rarely describe themselves as ill. Denial and ambivalence about change are common and are part of the disorder rather than resistance to help.

A useful clinical distinction is between anorexia nervosa and atypical anorexia nervosa. In atypical anorexia nervosa the core psychopathology is the same, but the person remains at or above a normal weight for age and sex. Medical complications can still be severe. Frequency and severity differ from underweight anorexia nervosa, so screening must not be limited to visibly underweight patients. NICE makes the same point: rapid weight loss and risk factors matter as much as the absolute BMI. (Kounatidis 2025; NICE NG69 1.2.6)

For a clinical diagnosis, paraphrase the three DSM-5-TR features:

1. Restriction of energy intake leading to a significantly low body weight for age, sex, developmental stage and physical health.
2. An intense fear of gaining weight or of becoming fat, or persistent behaviour that interferes with weight gain, present even when the patient is underweight.
3. A disturbance in the way body weight or shape is experienced, undue influence of body weight or shape on self-worth, or lack of recognition of the seriousness of the current low weight.

No laboratory test or imaging study makes this diagnosis. Weight is measured, but DSM-5-TR does not set a fixed BMI for diagnosis, and the Royal College and NICE approach deliberately avoids using a single weight or BMI cut-off to decide severity or admission. This protects the patient who loses weight rapidly from a normal baseline. It also means the clinician must assess the whole picture: weight trajectory, rate of loss, vital signs, electrolytes, behaviour and psychological features. Where diagnosis is uncertain, the eating-disorder service should be involved rather than the decision resting on one measure.

DSM-5-TR identifies two subtypes, and the distinction influences risk assessment and treatment planning:

• Restricting type: weight loss is achieved through dieting, fasting or exercise, without recurrent binge-eating or purging episodes during the current episode.
• Binge-eating/purging type: recurrent episodes of binge eating or purging (self-induced vomiting or misuse of laxatives, diuretics or enemas) occur during the current episode.

Subtypes overlap and can change over time; restrictive presentations can develop binge-purging features during refeeding. The binge-eating/purging type carries a higher risk of electrolyte disturbance, dental erosion and oesophageal injury, while the restricting type carries a higher risk of severe starvation, bradycardia, hypotension and refeeding complications.

Severity is not rated by BMI alone. NICE explicitly says not to use an absolute weight or BMI threshold to decide admission or treatment. In practice, however, a very low BMI informs urgency: one large review noted that bradycardia and hypotension often necessitate hospitalisation when BMI falls below 15 kg/m2, and that QTc prolongation becomes clinically significant when it exceeds 600 ms. Severity should therefore be described as a clinical judgement combining weight, rate of loss, vital signs, laboratory results and psychosocial functioning (Kounatidis 2025 ^[6]).

Epidemiology varies between populations and methods, and different reviews report different figures. A 2025 narrative review gives a lifetime prevalence of up to 4% in females and 0.3% in males (Kounatidis 2025 ^[6]). The APA press release accompanying its 2023 guideline quotes a US lifetime prevalence of approximately 0.80% for anorexia nervosa (0.28% for bulimia, 0.85% for binge-eating disorder), with estimates varying by location, demographics and diagnostic method (APA 2023 ^[2]). Both are consistent with anorexia nervosa being rare but serious: the lower figure reflects stricter case definitions and clinical ascertainment.

Onset is usually in adolescence or early adulthood. NICE notes that risk is highest between 13 and 17 years (NICE NG69 1.2.4 ^[1]), and diagnoses in children under 15 are rising, probably because of earlier onset and better recognition (Kounatidis 2025 ^[6]).

Risk factors are multifactorial and only partly modifiable. Aetiology includes genetic, epigenetic, sociocultural, psychiatric and biological influences. Family history, perfectionism and obsessive-compulsive traits, adverse childhood experience, high-performance environments (sport, dance, fashion, modelling), comorbid depression, anxiety or obsessive-compulsive disorder all increase risk. Eating disorders are frequently comorbid with diabetes, depression, anxiety, PTSD, substance misuse, OCD and ADHD, worsening outcome (NICE NG69 1.2.6; Kounatidis 2025 ^[6]).

Both sexes and all body types can be affected. The disorder requires particular vigilance when:

• A person has normal or higher weight but otherwise meets criteria (atypical anorexia nervosa).
• A male patient presents after excessive training or pursuit of muscularity; men are often diagnosed later, but the clinical consequences of starvation are the same (Mehler and Brown 2015 ^[5]).
• An adolescent shows falling height centiles, delayed puberty or delayed menarche.

Mortality is the central epidemiological fact. Anorexia nervosa has the highest mortality of any psychiatric disorder, through medical complications of malnutrition and through suicide, which is a leading cause of death in the first decade after diagnosis. Medical complications account for more than half of all deaths. Standardised mortality is substantially elevated, but reported ratios vary with severity, sex and treatment setting rather than reducing to one figure (Mehler and Brown 2015 ^[5]; Kounatidis 2025 ^[6]).

Starvation induces protein and fat catabolism, leading to loss of cellular volume and function. Almost every body system can be affected, and damage is greatest with greater weight loss and longer illness duration. The compensatory changes are adaptive in the short term and dangerous in the long term.

Cardiovascular adaptation produces bradycardia, seen in up to 95% of patients, and hypotension, reported in up to 85% in one review, correlating inversely with BMI, together with reduced left ventricular mass, pericardial effusion in up to one third in one review (and roughly 25-35% in echocardiography studies), and QTc prolongation in up to 40%. Heightened vagal tone lowers heart rate; structural changes follow chronic undernutrition. Most of these reverse with weight restoration (Kounatidis 2025 ^[6]; Mehler and Brown 2015 ^[5]).

Endocrine adaptation is equally important. In females, hypothalamic-pituitary-gonadal suppression produces functional hypogonadotropic hypogonadism: amenorrhoea occurs in up to 85% of cases, and about 20% of women do not resume menstruation even after normalising body weight. Leptin falls, ghrelin resistance develops, and hunger signals fail to drive eating because central reward and anxiety circuits are altered. The hypothalamic-pituitary-adrenal axis is overactive, with hypercortisolism; thyroid hormone conversion shifts toward rT3, producing a euthyroid sick picture in which TSH is usually normal. These responses are adaptive, not thyroid disease, so thyroid hormone replacement is not helpful and can be harmful (Kounatidis 2025 ^[6]; Mehler and Brown 2015 ^[5]).

Neurological consequences include brain atrophy, ventricular enlargement and cognitive rigidity, described in younger patients as resembling accelerated brain ageing. Some changes improve with refeeding, but recovery can be incomplete. Severe thiamine deficiency risks Wernicke encephalopathy (Kounatidis 2025 ^[6]; Mehler and Brown 2015 ^[5]).

Bone turns toward loss. Reduced osteoblastic activity combines with oestrogen or testosterone deficiency, low IGF-1, hypercortisolism and mineral depletion. Among women with anorexia nervosa, a large majority have osteoporosis or osteopenia (up to 85% in one review; site- and age-specific estimates differ), and men can be particularly severely affected (Mehler and Brown 2015 ^[5]).

Refeeding is the dangerous metabolic transition. When nutrition is reintroduced after starvation, the shift from catabolism to anabolism drives intracellular uptake of phosphate, potassium and magnesium, producing refeeding syndrome, typically in the first 10 days, and impairing myocardial energy metabolism. Hence the emphasis throughout management on cautious, monitored refeeding and electrolyte and thiamine supplementation (Kounatidis 2025 ^[6]; NICE NG69 1.11.9 ^[1]).

The history should be taken from the patient and, with consent, from family or carers, because insight is often poor.

• Eating and weight: dietary restriction, rules about food, fasting, low-fat or low-carbohydrate diets, calorie counting, fear of eating in front of others, preoccupation with menus, or binge-purging behaviour in the binge-eating/purging subtype.
• Fear and body image: intense fear of weight gain, body-checking, weighing, mirror-checking, misperception of specific body parts.
• Physical effects of starvation: fatigue, dizziness or fainting, palpitations, feeling cold, lanugo hair, hair loss, constipation, early satiety, bloating, abdominal pain.
• Endocrine: loss of menstrual periods in females, decreased libido and sexual function in males.
• Behavioural and mood: withdrawal from meals and friends, irritability, anxiety, depression, self-harm, suicidal thoughts, exercise beyond medical safety.
• Hidden presentations: abdominal pain, constipation, palpitations, anaemia, abnormal liver tests or unexplained hypoglycaemia may be the first presentation. NICE lists these as triggers for a high index of suspicion (NICE NG69 1.2.6 ^[1]).

Risk assessment is not a single score. It brings together:

• Physical risk: weight-loss rate (sometimes more than 1 kg per week), very low BMI or very low weight for age, bradycardia, hypotension, postural drop, hypothermia, ECG change, dehydration, hypokalaemia, hypoglycaemia, anaemia, deranged liver function.
• Nutritional risk: refusal or near-zero intake, water-loading, excessive exercise (more than 2 h/day while malnourished), vomiting or laxative/diuretic misuse.
• Mental health risk: depression, self-harm, suicidal intent, severe anxiety, severe body image disturbance, family conflict.
• Context: age, rate of change, family support, engaged carers, social vulnerability.

The MEED red-flag list converts this into an emergency screen (Mughal et al. 2023 ^[4]; Royal College MEED 2022 ^[3]).

A systems-based examination should be structured and repeated, because deterioration can be missed:

• General appearance and weight: marked loss of subcutaneous fat, wasting of temporal and proximal muscles, signs of dehydration.
• Vital signs: bradycardia below 60/min (often silent), hypotension, orthostatic drop, hypothermia, possibly below 35.5 °C tympanic temperature.
• Cardiovascular: quiet precordium, small or displaced apex, possible mitral valve prolapse murmur; resting tachycardia is unusual and suggests underlying infection or another complication.
• Skin: dry skin that may fissure and bleed at the fingers, lanugo hair along the sides of the face and spine, alopecia, acrocyanosis, easy bruising, pressure sores over bony prominences.
• Mouth and teeth: dental erosion and parotid enlargement in those who vomit; Russell's sign (knuckle calluses) from self-induced vomiting.
• Abdomen: epigastric fullness, distension, signs of superior mesenteric artery syndrome (pain after eating, early satiety, vomiting).
• Musculoskeletal: proximal weakness, difficulty sitting up from lying or rising from a squat, tenderness.
• Neurological: poor concentration, low mood, reduced awareness.

NICE recommends ECG monitoring when there is rapid weight loss, excessive exercise, severe purging, bradycardia below 40/min, hypotension, excess caffeine, medication risk, muscular weakness, electrolyte imbalance or a previous abnormal rhythm (NICE NG69 1.10.2 ^[1]).

Paediatric attention is required for delayed puberty, growth failure and delayed menarche, which may be the only signal that an adolescent is unwell.

Weight loss and food avoidance can arise from many organic and psychiatric disorders. The table gives the key separating features. A normal BMI does not exclude severe illness.

Diagnosis is clinical, but investigations quantify risk, exclude alternatives and measure complications. NICE recommends a physical health review at least annually, including weight or BMI, blood pressure, relevant blood tests and an ECG for those with purging or significant weight change. The table summarises tests and useful cut-offs.

| Height in children/adolescents | Growth faltering | Fall across centiles or delayed puberty. | | Pulse and blood pressure | Cardiovascular adaptation and risk | Bradycardia below 60 is common; MEED red flag is heart rate below 40; MEED red systolic blood pressure is below 90 mmHg in adults or below 0.4 centile for age with syncope or postural drop ^[4]. |

| Temperature | Hypothermia | MEED red flag below 35.5 °C tympanic ^[4]. |

| ECG | Arrhythmia risk | QTc prolongation; isolated relation to AN is uncertain; becomes clinically significant beyond 600 ms; medication and QT prolongation must be checked ^[6]. |

| Full blood count | Anaemia, leukopenia, thrombocytopenia | Anaemia and leukopenia each in about one third (higher as BMI falls); thrombocytopenia about 10%; cytopenias in up to 75% with severe disease; global meta-analysis anaemia estimate 44.8% ^[5][6]. |

| Renal profile and electrolytes | Dehydration, purging, renal dysfunction | Potassium below 2.5 mmol/L, hypoglycaemia below 3.0 mmol/L, hyponatraemia, hypocalcaemia, hypophosphataemia and hypoalbuminaemia are MEED red flags; impaired kidney function reported in about 37% in an adolescent cohort ^[4][6]. |

| Liver function tests | Starvation hepatitis vs refeeding | Elevated in almost half to more than half; starvation-induced rises more likely below BMI 12-13; marked rises 4 to 30 times normal can occur in severe disease ^[5][6]. |

| Thyroid function tests | Euthyroid sick syndrome | Low T3, high rT3, low-normal T4, usually normal TSH; avoid unnecessary thyroxine. | | Glucose | Hypoglycaemia risk | Recurrent hypoglycaemia indicates advanced disease and possible liver failure. | | Bone profile/25-hydroxyvitamin D | Bone health | To guide supplementation. | | Bone mineral density (DEXA/equivalent, adjusting for bone size in young patients) | Osteopenia/osteoporosis | NICE suggests scan after 1 year of underweight in children/young people and after 2 years in adults (earlier with bone pain or fractures); T-score below -1.0 (below -1.5 in some definitions) indicates osteopenia and below -2.5 osteoporosis using young-adult reference values ^[1][5]. |

| Pregnancy test/diabetes review | Perinatal and T1DE risk | Higher obstetric risk with AN; diabetologists coordinate care. |

Tests must be interpreted with BMI in mind. Creatinine can be misleadingly low in severe muscle wasting, so eGFR may underestimate renal impairment; alternative markers such as cystatin C are being studied. Serum albumin can remain normal despite severe malnutrition and should not be used alone as a nutritional marker (Kounatidis 2025 ^[6]).

Diagnosis is made from the longitudinal picture: low weight (or marked loss in atypical disease), restriction or other eating-disorder behaviours, fear of weight gain and body image disturbance, with exclusion of medical causes of weight loss.Severity should be integrated from all of these, not BMI alone.

Medical admission and urgent referral should be considered whenever MEED red flags appear. The MEED traffic-light system (green low risk, amber high concern, red impending risk to life) plans the location of care. Key red factors include:

• Rapid weight loss or more than 1 kg per week for two weeks ^[4].
• BMI under 13 in over-18s or m%BMI under 70% in under-18s ^[4].
• Heart rate below 40 beats/min, blood pressure below 90 mmHg in adults, syncope or postural drop, temperature below 35.5 °C tympanic ^[4].
• Fluid refusal, severe dehydration or acute food refusal; inability to sit up from lying or rise from squatting.
• ECG changes with prolonged QTc; multiple daily episodes of vomiting or laxative misuse.
• Electrolyte disturbances (potassium below 2.5 mmol/L, glucose below 3.0 mmol/L, hyponatraemia, hypocalcaemia, hypoalbuminaemia, hypophosphataemia), anaemia below 10 g/L or transaminases above three times the normal range ^[4].
• Severe self-harm or high suicide risk, high exercise (more than 2 h/day while malnourished), poor insight or resistance to weight gain from fear, life-threatening medical conditions or HbA1c above 10% in patients with diabetes (Mughal et al. 2023 ^[4]).

When these are present, urgent assessment and/or admission is needed. NICE adds that admission may be to a medical inpatient or day-patient service for medical stabilisation and refeeding if outpatient treatment is unsafe; no absolute weight or BMI threshold is used; and if the person refuses, Mental Health Act (or equivalent) assessment may be needed (NICE NG69 1.11.1-1.12.2 ^[1]).

Management is multidisciplinary: medical stabilisation, nutritional rehabilitation and psychological therapy, in a coordinated plan with the person and carers.

• Refer early: NICE recommends immediate referral to a community-based, age-appropriate eating-disorder service when the disorder is suspected after initial assessment. Early treatment matters particularly for those at risk of severe emaciation. Do not let BMI alone decide whether to treat (NICE NG69 1.2.8-1.2.10 ^[1]).
• Medical stabilisation: provide acute medical care for severe electrolyte imbalance, severe malnutrition, severe dehydration or incipient organ failure. If admission is needed for stabilisation and refeeding, involve the eating-disorder or liaison psychiatry service throughout and keep family involved (NICE NG69 1.10.3, 1.11.1, 1.11.7 ^[1]).
• Outpatient vs inpatient: most patients without worsening symptoms can be treated as outpatients, especially with family support. Bradycardia below 40, prolonged QT, severe dehydration or rapidly changing values point toward inpatient care under MEED and NICE (NICE NG69 1.11.3 ^[1]; Mughal et al. 2023 ^[4]).
• Feeding and refeeding: use a standard operating procedure for refeeding that avoids both under-nutrition and refeeding syndrome, referring to MEED. Offer electrolytes orally if supplementation is needed, unless gastrointestinal absorption is impaired or the disturbance is severe. Give thiamine-containing multivitamins before and during early feeding, correct electrolytes, and monitor until stable. Rate of increase and final energy prescription are set locally following a refeeding protocol under dietetic supervision (NICE NG69 1.10.4, 1.11.9-1.11.10 ^[1]; Mughal et al. 2023 ^[4]).
• Vitamins and supplements: encourage an age-appropriate oral multivitamin and mineral supplement until the diet is adequate, and include carers in meal planning for children and adolescents (NICE NG69 1.3.20-1.3.23 ^[1]).
• Compulsory treatment: where physical health is at serious risk and the person will not consent, and safe treatment is only possible in hospital, use the legal framework for compulsory treatment (Mental Health Act in England/Wales, or equivalent). Feeding without consent must be by a competent multidisciplinary team (NICE NG69 1.12.1-1.12.3 ^[1]).

NICE treatment options for adults with anorexia nervosa are:

• CBT-ED: up to 40 sessions over 40 weeks, with twice-weekly sessions in the first 2-3 weeks; nutrition, cognitive restructuring, mood regulation, social skills, body image, self-esteem and relapse prevention ^[1].
• MANTRA: usually 20 sessions, weekly for the first 10 weeks, with up to 10 more for complex problems; motivation, a workbook, and involvement of family or carers ^[1].
• SSCM: 20 or more weekly sessions; psychoeducation and nutritional advice, physical monitoring, a weight range goal and a positive therapeutic relationship ^[1].
• FPT (focal psychodynamic therapy): up to 40 sessions over 40 weeks if CBT-ED, MANTRA or SSCM is unacceptable, contraindicated or ineffective (NICE NG69 1.3.4-1.3.9 ^[1]).

APA recommends eating-disorder-focused psychotherapy for patients with anorexia nervosa, encompassing normalisation of eating and weight-control behaviour, weight restoration and addressing psychological aspects such as fear of weight gain and body image disturbance (APA 2023 ^[2]).

NICE recommends:

• Family therapy for anorexia nervosa (FT-AN): typically 18-20 sessions over one year, with reviews at 4 weeks and then every 3 months to set the pace. Initially parents take a central, temporary role in re-establishing eating; later treatment supports age-appropriate independence; relapse prevention is included. This is the family-based treatment endorsed by APA for adolescents and emerging adults who have an involved caregiver (NICE NG69 1.3.10-1.3.11 ^[1]; APA 2023 ^[2]).
• If FT-AN is unacceptable or ineffective: individual CBT-ED for children/young people (up to 40 sessions over 40 weeks with additional family sessions) or adolescent-focused psychotherapy for anorexia nervosa (32-40 sessions over 12-18 months) ^[1].
• Support for carers and family members not directly involved, and separate sessions for the young person, are also recommended (NICE NG69 1.3.12-1.3.17 ^[1]).

NICE says not to offer medication as the sole treatment for anorexia nervosa. Evidence for pharmacological treatment of the eating disorder itself is limited; medication is used for comorbid conditions (depression, anxiety, OCD), chosen with care because malnutrition and purging alter drug effectiveness and risk side effects. ECG monitoring is advised for medication that could affect cardiac function, particularly with bradycardia below 40, hypokalaemia, electrolyte disturbance or a prolonged QT. Antipsychotic or other agents may in practice be considered for weight-related anxiety in specialist settings, but none is an established, universally recommended treatment; if used, this must follow local specialist protocols (NICE NG69 1.3.24, 1.8.14-1.8.17 ^[1]).

Weight alone is not the endpoint; the aim is medical stabilisation, restored eating and psychological recovery. NICE directs that:

• An oral multivitamin/mineral supplement should be encouraged until diet is adequate; dietary counselling should only be given as part of multidisciplinary care.
• For children and adolescents, supplementary dietary advice should support growth and development, particularly during puberty.
• A GP should offer a physical and mental health review at least annually for people not in ongoing treatment, including weight/BMI, blood pressure, blood tests, daily functioning, physical and mental risk, ECG (for purging or significant weight change) and discussion of treatment options (NICE NG69 1.3.20-1.3.23, 1.10.10 ^[1]).
• ECG and bloods are reassessed as needed, particularly in the first weeks of refeeding and if purging continues.

Low body weight is the main driver of low bone density, and the single best prevention and treatment is reaching and maintaining a healthy body weight. NICE recommendations include:

• A bone-density scan is considered after 1 year of underweight in children and adolescents (or earlier with bone pain or recurrent fractures) and after 2 years in adults (or earlier) ^[1].
• Scans should not be repeated more than once a year unless bone pain or recurrent fractures occur ^[1].
• Do not routinely offer oral or transdermal oestrogen therapy to children or adolescents.
• Consider transdermal 17-beta-oestradiol (with cyclic progesterone) for young women aged 13-17 with long-term low body weight, low bone density and bone age over 15; physiological oestrogen for bone age under 15; bisphosphonates for women aged 18 or over with long-term low weight and low bone density, with counselling about teratogenicity ^[1].
• Advise avoidance of high-impact or fall-risk activities in patients with osteoporosis or related bone disorders (NICE NG69 1.10.12-1.10.24 ^[1]).

Refeeding syndrome is a potentially fatal shift in fluids and electrolytes during the early phase of nutritional repletion. It typically appears within the first 10 days, with hypophosphataemia, hypokalaemia and hypomagnesaemia, and may present with peripheral oedema, acute fluid overload, cardiorespiratory failure, organ dysfunction and rising transaminases. Thiamine deficiency can worsen cardiac function (Kounatidis 2025 ^[6]; Mughal et al. 2023 ^[4]).

Prevention and treatment, following NICE (which refers to MEED for a standard operating procedure), are:

• Risk-stratify before feeding using MEED red factors (low BMI, very low intake, recent very rapid weight loss, low electrolytes, alcohol misuse, peripheral oedema, serious systemic illness).
• Start nutrition slowly and increase under specialist and dietetic supervision; give thiamine and multivitamins before and during early refeeding; correct electrolytes and monitor them daily until stable. Late refeeding syndrome can occur, so monitoring is often continued beyond initial stabilisation.
• If RFS occurs, reduce or pause nutritional advancement, replace phosphate, potassium and magnesium, manage fluid overload and involve the treating team urgently (NICE NG69 1.10.4, 1.11.9-1.11.10 ^[1]; Mughal et al. 2023 ^[4]).

When type 1 diabetes coexists with anorexia nervosa, insulin omission may be used for weight control. Teams should not stop insulin altogether; rapid drops in blood glucose should be avoided (risk of retinopathy and neuropathy), blood glucose and ketones require close monitoring, and gradually increasing carbohydrate and insulin doses is used under specialist supervision. Nutritional rehabilitation should be coordinated between eating-disorder and diabetes services. HbA1c above 10% is a MEED red flag (Mughal et al. 2023 ^[4]; NICE NG69 1.8.3-1.8.11 ^[1]).

Medical complications are a direct result of weight loss, malnutrition and compensatory behaviour; they become more common as weight falls and illness becomes chronic, and they account for over half of deaths (Mehler and Brown 2015 ^[5]).

| Refeeding | Refeeding syndrome, symptomatic refeeding, peripheral oedema, cardiorespiratory failure, life-threatening hypophosphataemia. | | Gastrointestinal | Delayed gastric emptying (gastroparesis) below roughly 15-20% of ideal body weight, constipation, acute gastric dilation (rare, life-threatening), superior mesenteric artery syndrome, dysphagia with aspiration, pancreatitis during refeeding, abnormal liver tests in almost half to more than half (pronounced with BMI below 12-13) ^[5][6]. |

| Hepatic | Starvation-induced transaminase elevation, steatosis/steatohepatitis during refeeding, hepatocyte autophagy; acute liver failure is rare. | | Endocrine/metabolic | Amenorrhoea (up to 85%), hypothalamic hypogonadism, low oestrogen/testosterone, hypercortisolism, euthyroid sick syndrome, hypoglycaemia (dangerous when advanced), growth failure in children/adolescents, infertility and unplanned pregnancy ^[6]. |

| Bone and muscle | Osteopenia/osteoporosis (up to 85% of women), sarcopenia, falls, fractures, impaired peak bone mass in adolescents ^[5]. |

| Haematological | Anaemia (meta-analysis estimate 44.8%), leukopenia (often the predominant abnormality), thrombocytopenia (around 10%), pancytopenia in severe disease (up to 75%); atypically little fever/inflammation may mask infection ^[5][6]. |

| Neurological | Brain atrophy, ventricular enlargement, cognitive rigidity, risk of Wernicke encephalopathy with thiamine deficiency, neuropathy in severe cases. | | Renal | Hypokalaemic nephropathy, acute kidney injury, chronic kidney disease; impaired kidney function in about 37% in an adolescent cohort ^[6]. |

| Pulmonary | Spontaneous pneumothorax, pneumomediastinum, aspiration pneumonia, nutritional emphysema in case reports. | | Skin/hair | Xerosis, lanugo, alopecia, acrocyanosis; skin signs particularly when BMI falls below 16; Russell's sign and dental erosion in purging ^[6]. |

| Pregnancy/neonatal | Higher rates of miscarriage, low birth weight, preterm delivery and intrauterine growth restriction if pregnancy occurs during illness. |

Refeeding can unmask or worsen medical problems transiently (electrolyte fall, oedema, liver test rise), so improvement does not track weight exactly in the first weeks.

The prognosis is guarded but can be good with early, sustained treatment:

• Anorexia nervosa has the highest mortality rate among psychiatric disorders; standardised mortality is substantially elevated (estimates vary with severity, sex and treatment setting), and medical complications account for more than half of deaths. Suicide is a leading cause and is most prominent in the first 10 years (Kounatidis 2025 ^[6]; Mehler and Brown 2015 ^[5]).
• Most physical complications are reversible with weight restoration, including bradycardia, hypotension, QT changes, cardiac structural change, pericardial effusion, liver tests and amenorrhoea (although 20% of women do not resume menses) and many haematological abnormalities (Mehler and Brown 2015 ^[5]; Kounatidis 2025 ^[6]).
• Bone deficits and some neural changes may persist, especially after adolescent onset before peak bone mass.
• Relapse and chronicity are common; improvement usually needs specialised, sustained treatment and family or carer support.
• Early referral, higher engagement and younger age at treatment generally improve outcome; NICE emphasises earliest possible treatment, particularly for those at risk of severe emaciation (NICE NG69 1.2.1-1.2.2 ^[1]).

Avoid over-promising: a single admission for weight gain is not recovery; relapse planning and continuous support matter as much as restoring weight.

There is no single proven preventive intervention, but guidelines agree on systematic detection and early intervention:

• NICE: eating disorders can present at any age, but risk is highest at 13-17 years; do not use screening tools (such as SCOFF) as the sole diagnostic method; identify risk through the warning signs; refer immediately to specialist services when suspected; treat at the earliest opportunity (NICE NG69 1.2.4-1.2.10 ^[1]).
• APA: screening for the presence of an eating disorder should be part of an initial psychiatric evaluation; US public-health guidance on universal screening remains limited (APA 2023 ^[2]).
• NICE: for people with AN not receiving treatment, GPs should offer a physical and mental health review at least annually (NICE NG69 1.10.10 ^[1]).
• Primary prevention centres on education about eating-disorder myths, weight stigma, healthy (not restrictive) eating and prompt management of adolescent weight concerns; the best evidence supports strengthening family and school environments and addressing comorbid mental health problems. Routine body-mass screening should not be used to diagnose AN; gradual, health-oriented weight management, not restrictive dieting, is the safe approach.

• NICE definitions: children 0-12 years, young people 13-17 years; risk is highest 13-17 (NICE NG69, terms ^[1]).
• Growth and puberty need active monitoring; delayed menarche or falling height centiles may be the only clue.
• FT-AN is the treatment of choice; involve parents early as temporary leaders of refeeding; provide separate sessions for the young person.
• Bone-density scans considered after 1 year of underweight (or earlier with bone pain or fractures); do not routinely use hormones; consider transdermal oestrogen regimens on specialist paediatric/endocrinology advice.
• Medication should not be sole treatment; growth-failure advice from paediatrics or endocrinology (NICE NG69 1.3.10-1.3.17, 1.8.20, 1.10.11-1.10.22 ^[1]).

• CBT-ED, MANTRA or SSCM are recommended psychotherapies. Focal psychodynamic therapy is an option for non-responders.
• Ongoing physical health monitoring and bone-health surveillance; annual review applies if not in specialist care.
• Long-term ill adults may need social, occupational and carer support, plus management of chronic bone disease and dental problems.

Older adults can present with anorexia nervosa, sometimes after bereavement, loneliness or physical illness. The danger of hypoglycaemia rises with age and severity. Assessment and management follow the same principles, but there is higher vigilance for comorbidity, polypharmacy and frailty. Evidence on age-specific outcomes is limited, so care should follow specialist advice (Mehler and Brown 2015, older adults and hypoglycaemia ^[5]).

Men often present later, with stigma; clinical findings are equivalent or more severe because of lower fat reserves. Include testosterone and LH/FSH in the endocrine assessment; low testosterone correlates with low bone density (Mehler and Brown 2015 ^[5]).

Women with anorexia nervosa can ovulate and conceive despite amenorrhoea, and unplanned pregnancy is a risk. Pregnancy in AN increases miscarriage, preterm delivery, low birth weight and intrauterine growth restriction. NICE recommends advice and education when planning conception (adequate nutrient intake, healthy body weight, reducing restriction and compensatory behaviours), nomination of a dedicated professional to monitor and support during pregnancy and the postnatal period, offering eating-disorder treatment during pregnancy, and considering more intensive prenatal care for current or remitted AN (NICE NG69 1.9.1-1.9.5 ^[1]; Mehler and Brown 2015 ^[5]; Kounatidis 2025 ^[6]).

Where specialist services, dietitians, bone densitometry or refeeding protocols are unavailable:

• Use a single page of observations (pulse, blood pressure sitting/standing, temperature, weight, hydration, swelling) and refer rather than trying to make complex risk decisions locally.
• Weigh with a reliable scale and record change over time; use BMI or centile charts, but do not rely on BMI alone.
• A baseline set of blood tests (FBC, U&E, LFT, glucose, phosphate, magnesium, calcium, albumin) and an ECG should be obtained before or during refeeding if at all possible.
• If medications for complications are limited, prioritise safety: stop dangerous purging, avoid QT-prolonging drugs, give vitamin B complex/thiamine, encourage oral refeeding and fluids, and escalate early.
• Refer severe cases early to the nearest hospital able to provide monitored refeeding; prevention of refeeding syndrome matters as much as weight gain.
• Keep families involved; family-based refeeding at home under supervision is often the only available option.

• Anorexia nervosa is a psychiatric disorder of behaviours and cognitions, not simply a low weight.
• It has the highest mortality of psychiatric disorders; assess risk at every contact and act on red flags.
• Diagnosis is clinical; use BMI trajectory, vital signs and laboratory findings rather than one cut-off.
• Medical complications touch nearly every system, but most reverse with weight restoration.
• Refeeding can be as dangerous as starvation; prevention and monitoring are essential.
• Treatment combines medical stabilisation, nutritional rehabilitation and evidence-based psychotherapy; medication alone is insufficient.
• FT-AN is the first-line psychological treatment for children and adolescents with AN; CBT-ED, MANTRA and SSCM are options for adults ^[1].
• Bone health is best protected by reaching and maintaining a healthy weight.
• Pregnancy is possible despite amenorrhoea and carries increased risk for mother and fetus.
• Early recognition and referral improve outcome.

Eating-disorder service models, bulimia nervosa, binge-eating disorder, ARFID, depression, anxiety, obsessive-compulsive disorder, type 1 diabetes and disordered eating (T1DE), osteoporosis, malnutrition.