🍽️ Loss of Appetite & Unintentional Weight Loss in Adults

The RCPsych MEED guidance (CR233; replaced MARSIPAN) uses a multidomain traffic-light risk assessment — rate of weight loss, BMI or age-adjusted measures, cardiovascular findings (bradycardia, hypotension, orthostatic changes, ECG), temperature, hydration, electrolytes and glucose, muscle function, purging and psychiatric risk — and the admission decision depends on the whole clinical picture; NICE NG69 advises against using a single BMI or weight threshold. Under-18s need age- and sex-adjusted measures, not adult thresholds. GPs who see patients with anorexia nervosa must perform or arrange an urgent physical assessment including ECG, electrolytes, glucose, and lying/standing blood pressure. The cardiac risk in severe anorexia nervosa is substantial — bradyarrhythmias (from vagal overactivity + electrolyte imbalances) and QTc prolongation (from hypokalaemia, hypomagnesaemia) can cause sudden cardiac death, particularly during refeeding. NICE NG69 (Eating disorders, 2017, which replaced CG9) and the RCPsych MEED guidance (2022, which replaced MARSIPAN) provide the framework. Refeeding syndrome is the most important acute complication of treating severe malnutrition and anorexia — the pathophysiology involves: during prolonged starvation, the body shifts to fat/protein catabolism. Intracellular electrolytes (phosphate, potassium, magnesium) remain relatively preserved despite depletion of total body stores. When carbohydrates are reintroduced, insulin secretion drives glucose, potassium, phosphate, and magnesium back into cells simultaneously, causing precipitous plasma falls. Hypophosphataemia (<0.3 mmol/L) is the critical trigger for cardiac failure, respiratory muscle weakness, and rhabdomyolysis. For high-risk patients NICE CG32 advises: start at a maximum of 10 kcal/kg/day (5 kcal/kg/day in extreme cases such as BMI <14 or negligible intake for >15 days, with continuous cardiac monitoring), increasing to full requirements by day 4–7; thiamine 200–300 mg daily immediately before and during the first 10 days; potassium, phosphate and magnesium supplementation unless levels are high; and close monitoring of fluid balance, clinical status, glucose, U&E, magnesium and phosphate. This is a specialist-supervised protocol, not unsupervised primary-care refeeding.

The paraneoplastic anorexia-cachexia syndrome (CACS) deserves emphasis as a clinically important and pathophysiologically distinct entity from simple anorexia from reduced intake — in CACS, the weight loss is disproportionate to the degree of anorexia because of active catabolism of muscle protein (proteolysis-inducing factor, IL-6, TNF-α drive muscle wasting independent of caloric intake). This means that simply increasing caloric intake does not reverse the muscle wasting in CACS — the patient continues to lose lean body mass even with supplemental nutrition. CACS is a major negative prognostic indicator (cancer patients with cachexia die earlier than matched patients without cachexia, independent of tumour stage). Understanding CACS changes the management approach: the goal is not to 'feed them more' but to address symptoms (nausea, early satiety, dysphagia, pain), optimise nutritional intake within the physiological constraints, and focus on quality of life. Megestrol acetate and corticosteroids improve appetite temporarily but do not improve survival or lean mass, and are specialist/palliative-care treatments only. This is covered in the corticosteroids in palliative care protocol. The GLP-1 agonist (semaglutide, liraglutide) mechanism of appetite suppression is now clinically important because these drugs are widely prescribed for type 2 diabetes and obesity. GLP-1 agonists suppress appetite via: (1) direct hypothalamic GLP-1 receptor activation reducing hunger signals; (2) delayed gastric emptying causing early satiety; (3) inhibiting the ghrelin (hunger hormone) system. The profound appetite suppression they cause (contributing to 10–15% body weight loss) is the therapeutic mechanism, but in some patients — particularly elderly patients, those with low baseline BMI, or those with concurrent illness — this appetite suppression can become a genuine clinical problem causing malnutrition. GPs must document weight at every diabetes review for patients on GLP-1 agonists and reduce the dose or stop the drug if unintended weight loss occurs.

The MUST (Malnutrition Universal Screening Tool) score is the recommended nutritional screening tool for primary care and hospital outpatients — it takes 3 minutes to calculate and provides a standardised risk score that determines the urgency of dietitian referral and intervention. MUST score ≥2 = high malnutrition risk, prompting active intervention and referral per local arrangements. The three components are: (1) BMI score: BMI >20 = 0 points; 18.5–20 = 1 point; <18.5 = 2 points. (2) Unintentional weight loss score: <5% = 0 points; 5–10% = 1 point; >10% = 2 points. (3) Acute illness score: if acutely ill and no nutritional intake for >5 days = 2 points. Total MUST score: 0 = low risk (routine care); 1 = medium risk (dietary advice, monitor); ≥2 = high risk (intensive dietetic input). The SCOFF questionnaire is a screening aid for eating disorders, not a diagnostic gatekeeper: (1) Do you make yourself Sick because you feel uncomfortably full? (2) Do you worry you have lost Control over how much you eat? (3) Have you recently lost more than One stone in a 3-month period? (4) Do you believe yourself to be Fat when others say you are too thin? (5) Would you say that Food dominates your life? A score of ≥2 supports further assessment; a negative score does not exclude an eating disorder. The SCOFF should be administered sensitively, with a non-judgmental framing — patients with eating disorders frequently deny or minimise symptoms, particularly weight-related questions.

The succession splash test for gastroparesis is a rarely performed but diagnostically useful bedside test — the patient fasts for 4 hours, the examiner places a stethoscope over the epigastrium and rapidly shakes the patient's torso. A splashing sound heard more than 4 hours after the last meal indicates retained gastric fluid (gastroparesis, pyloric stenosis, gastric outlet obstruction). It is quick, non-invasive, and can guide whether urgent upper GI imaging is needed. The CT chest/abdomen/pelvis investigation threshold for unexplained significant weight loss is lower than many GPs realise — NICE NG12 (updated April 2026) sets site-specific weight-loss criteria — for example, consider an urgent direct-access CT (within 2 weeks) for pancreatic cancer at age 60 and over with weight loss plus diarrhoea, back pain, abdominal pain, nausea, vomiting, constipation or new-onset diabetes. Outside those criteria, many areas offer a non-specific symptoms pathway that includes CT when unexplained weight loss comes with abnormal first-line results (anaemia, raised ESR/CRP, abnormal LFTs, hypercalcaemia). Access to CT follows the NG12 criteria and local non-specific symptoms pathway arrangements.

NICE NG69 (2017, which replaced CG9) asks for immediate referral to eating disorder services rather than waiting for the patient to become 'ready' or for weight to reach a threshold — this reflects the evidence that early intervention in anorexia nervosa produces significantly better outcomes (higher rates of full recovery, lower mortality) than delayed treatment. Anorexia nervosa has a high mortality, and the risk of death is highest in the first years after diagnosis. Every month of delay in accessing specialist eating disorder treatment represents increased risk. GPs should make the CEDS referral immediately on identification of a likely eating disorder, while continuing to provide primary care support, regular physical monitoring, and engagement. In the under-18s, the NHS England access and waiting time standard for children and young people with an eating disorder (2015) specifies that young people with suspected eating disorders should be seen within 1 week for urgent cases and 4 weeks for routine referrals — GPs should specify 'urgent' on the referral if there is any physical compromise or rapid weight loss. ARFID (Avoidant/Restrictive Food Intake Disorder) is a DSM-5 diagnosis that describes food refusal based on sensory characteristics, fear of aversive consequences (choking, vomiting), or apparent lack of interest in food — without the body image disturbance of anorexia nervosa. It is increasingly recognised in adults (not just children) and is seen more frequently in patients with autism spectrum disorder, anxiety disorders, and OCD. GPs who encounter patients with longstanding selective eating patterns causing nutritional deficiency or weight loss should consider ARFID and refer to the appropriate local service (eating disorders team or psychology).

Mirtazapine is a particularly useful antidepressant for the combination of depression + anorexia + insomnia that frequently presents in elderly patients or those with chronic illness — its mechanism (noradrenergic and specific serotonergic antidepressant, NASSA) includes potent H1 histamine receptor antagonism at 15 mg, which increases appetite and promotes weight gain. At higher doses (30–45 mg), the noradrenergic effects are more prominent and the appetite-stimulating H1 effect is relatively less pronounced — but it should be prescribed for a clear depressive disorder, not as a general appetite stimulant. Olanzapine is sometimes used by specialist teams in refractory anorexia nervosa. NICE NG69 (2017, updated 2020) advises against offering medication as the sole treatment for anorexia nervosa and does not recommend olanzapine routinely; specialist teams sometimes use it as an adjunct in severe, refractory AN where other treatments have failed. It is initiated by the eating disorders team, not in primary care, but GPs should be aware of this option when discussing treatment options with patients.

The prescribing of oral nutritional supplements (ONS) on NHS prescription is an important and underused intervention in primary care — the ACBS (Advisory Committee on Borderline Substances) specifies the conditions in which ONS can be prescribed on FP10: disease-related malnutrition, pre-operative preparation of malnourished patients, dysphagia, proven inflammatory bowel disease, following total gastrectomy, short bowel syndrome, and intractable malabsorption (specifically, not for general 'feeling unwell' or 'poor appetite' without nutritional compromise). For GP prescribers, ACBS indications, local formulary policy and product availability apply; select products with dietetic or local formulary advice and check current product information rather than relying on remembered energy/protein values. Ondansetron-induced constipation is a very common and practically important side effect — ondansetron (a 5-HT3 receptor antagonist) dramatically reduces bowel motility. In already anorexic patients, constipation further reduces appetite (abdominal fullness, bloating). Consider a laxative alongside ondansetron where constipation is a risk.

The social eating evidence is strong and clinically relevant — studies consistently show that elderly people living alone eat less than those living with others, with social mealtimes producing automatic appetite improvement independent of the food available. The mechanism involves social facilitation of eating behaviour (mirroring, reduced self-monitoring, improved mood) and the structure and ritual of a shared meal. Community interventions (lunch clubs, Meals on Wheels, befriending services) produce measurable improvements in nutritional intake and quality of life in elderly isolated patients. GPs who identify social isolation as a contributing factor in elderly anorexia should actively refer to social services and community befriending services — these are evidence-based nutritional interventions even though they are social rather than medical. Ginger (tea or biscuits) is a simple dietary measure that some people find helpful for mild nausea; the evidence is limited, and it does not replace treating the cause or choosing an antiemetic according to the cause.

Unexplained weight loss needs an active, documented plan rather than open-ended watchful waiting: review within 1–4 weeks according to trajectory and risk, and if first-line investigations are reassuring but weight loss continues, use the NG12 or local non-specific symptoms pathway. The family counselling around reduced oral intake in dying patients is one of the most important and emotionally charged conversations in palliative primary care — many families interpret reduced eating in a dying patient as 'giving up' or 'not being fed properly' and request interventional feeding (NG tube, PEG, TPN). Providing accurate, compassionate information that reduced oral intake is a normal part of the dying process (reduced metabolic demand, reduced gut absorption, central appetite suppression from disease) and that forced feeding in the dying causes discomfort without benefit or survival extension is a core GP communication skill. The palliative pain protocol addresses this context further. NICE NG31 (Care of Dying Adults) specifically states that artificial nutrition and hydration should not be started routinely in the last days of life unless there is a specific clinical indication and it is consistent with the patient's wishes.