Cancer cachexia and nutrition

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

Cancer cachexia differs from simple starvation. In starvation, metabolic adaptation conserves protein and tissue can return when intake resumes. In cachexia, inflammatory and neuroendocrine signals continue proteolysis, lipolysis and insulin resistance despite food. Weight loss above 5% over six months, or smaller loss with low BMI or sarcopenia, supports diagnosis. Oedema and obesity can conceal muscle loss, so ask about strength, stairs, grip, clothing and previous imaging as well as scales.

Assessment seeks reversible barriers before prescribing calories. Examine mouth and teeth, swallowing, abdomen, stool, hydration, oedema, muscle and functional performance. Review pain, nausea, constipation, taste, mood, food access and treatment. Blood count, renal, liver, calcium, magnesium, phosphate, glucose, thyroid or cortisol testing follows the phenotype. Pancreatic cancer and surgery may cause enzyme deficiency, while head-and-neck treatment can make swallowing unsafe.

A dietitian builds food around symptoms, preferences and goals. Energy- and protein-dense small meals, fortification and oral supplements are first line when the gut works. A feeding tube can bridge curative head-and-neck treatment or a reversible swallowing problem. Parenteral nutrition is considered for intestinal failure, not because any patient is losing weight. Expected duration, performance, cancer control, home support and line risk determine whether it can improve survival or function.

Refeeding risk must be assessed before ambitious support. Start slowly, replace vitamins and electrolytes and watch fluid. In progressive refractory cachexia, nutrition cannot reverse the biology. The therapeutic focus shifts to symptom relief, easy preferred foods, mouth care and reducing conflict. Appetite stimulants can provide brief benefit for selected goals but do not rebuild muscle or cure cachexia; clinicians should say this plainly and compassionately.

Key points

Cancer cachexia is a multifactorial syndrome of ongoing muscle loss, with or without fat loss, that cannot be fully reversed by conventional nutrition alone.
A practical diagnostic threshold is weight loss above 5% over six months, or above 2% with BMI below 20 kg/m² or established sarcopenia, after clinical context is checked.
First-line assessment records current and usual weight, percentage and rate of loss, intake, symptoms, muscle function, inflammation, cancer trajectory and treatment intent.
Screen at diagnosis and repeatedly during treatment with a validated tool such as MUST, but use dietetic assessment rather than a score alone to prescribe care.
Treat reversible causes first: pain, nausea, constipation, mucositis, candidiasis, depression, dysphagia, obstruction, hypercalcaemia, endocrine failure and pancreatic insufficiency.
First-line nutrition support is individualised dietary counselling, energy- and protein-enrichment, preferred small frequent foods and oral supplements when ordinary intake remains inadequate.
Combine nutrition with resistance and aerobic activity as tolerated because feeding without a muscle stimulus cannot fully address sarcopenia.
Use enteral feeding when the gastrointestinal tract is functional but swallowing or intake cannot meet a realistic goal; use parenteral nutrition only when the gut is inaccessible or non-functional and expected benefit exceeds burden.
Artificial nutrition is not routine treatment for refractory cachexia in the last phase of life and should never be framed as preventing starvation when the dying body cannot use nutrition normally.
Before feeding, identify NICE high risk for refeeding from low BMI, major recent weight loss, little intake, low phosphate, potassium or magnesium, alcohol or relevant drug exposure.
For high refeeding risk, start nutrition slowly, commonly no more than 10 kcal/kg/day, give thiamine 200 to 300 mg daily and replace electrolytes with close cardiac and fluid monitoring.
In extreme risk, such as BMI below 14 kg/m² or negligible intake for more than 15 days, NICE advises about 5 kcal/kg/day with continuous rhythm monitoring.
A short corticosteroid course can transiently improve appetite and wellbeing when prognosis is short, but muscle weakness, delirium, infection and hyperglycaemia limit duration.
Pancreatic enzyme replacement should accompany meals and snacks in pancreatic exocrine insufficiency; increase and review delivery before assuming supplements have failed.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Tumour-driven systemic inflammation

Cytokines from tumour and host alter appetite, hypothalamic signalling, insulin sensitivity and protein and lipid turnover, producing muscle loss disproportionate to intake.

Mechanical and treatment barriers

Dysphagia, obstruction, mucositis, xerostomia, nausea, diarrhoea, pain, early satiety and altered taste reduce intake and may be reversible or bypassed.

Malabsorption and organ insufficiency

Pancreatic enzyme deficiency, bile or bowel disease, short bowel, fistula and treatment-related enteropathy prevent nutrients reaching the circulation despite apparently adequate eating.

Psychosocial and access factors

Depression, anxiety, fatigue, isolation, poverty, cooking difficulty and conflict over food can amplify nutritional decline and require practical rather than purely medical support.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Negative protein balance
Inflammatory and tumour signals increase proteolysis and blunt muscle protein synthesis, so ordinary calorie replacement alone cannot fully restore lean mass.
2
Altered energy metabolism
Insulin resistance, increased hepatic substrate cycling, lipolysis and variable resting energy expenditure waste energy and contribute to fat and muscle depletion.
3
Anorexia and early satiety
Hypothalamic signalling, taste change, delayed gastric emptying, ascites and organ enlargement reduce desire and capacity to eat before obvious obstruction develops.
4
Sarcopenia reduces resilience
Loss of skeletal muscle impairs strength, ventilation, immunity, treatment tolerance and independence even when body weight or body mass index remains deceptively high.
5
Refeeding shifts electrolytes intracellularly
Carbohydrate-induced insulin drives phosphate, potassium and magnesium into cells, expands sodium and water and depletes thiamine, threatening heart, brain and respiratory muscle.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Progressive involuntary weight loss

A fall in weight, clothes size or mid-arm and temporal bulk despite effort suggests active catabolism and requires percentage and rate calculation.

Sarcopenic function loss

Reduced grip, slower walking, difficulty rising from a chair and loss of independence may reveal muscle depletion before a low BMI appears.

Nutrition-impact symptoms

Dry mouth, altered taste, early satiety, nausea, pain, dysphagia, diarrhoea and constipation identify treatable barriers and shape route and food texture.

Unsafe swallowRed flag

Coughing, voice change, choking, prolonged meals or recurrent chest infection needs urgent speech-and-language assessment before unrestricted oral intake.

Refeeding syndromeRed flag

Oedema, tachycardia, arrhythmia, confusion, weakness, seizures or breathlessness after feeding starts demands immediate electrolyte and thiamine management.

Refractory cachexia

Progressive catabolism with poor performance and cancer unresponsive to treatment indicates limited reversibility and shifts goals toward comfort and family support.

Red flags requiring action

Rapid unintentional weight loss, inability to eat for more than five days or a body mass index below 18.5 requires prompt nutrition-risk and refeeding assessment.
Coughing, wet voice, recurrent chest infection or choking during intake suggests unsafe swallowing and needs speech-and-language assessment before unrestricted oral feeding.
Persistent vomiting, colic, distension or absent stool and flatus suggests obstruction; oral supplements or prokinetics may worsen risk until anatomy is clarified.
New oedema, tachycardia, arrhythmia, confusion, weakness or breathlessness after nutrition starts may be refeeding syndrome even before a laboratory value becomes profoundly abnormal.
Fever, oral ulceration, odynophagia, jaundice, severe diarrhoea or uncontrolled pain can reveal a reversible treatment or disease complication driving reduced intake.
Hyperglycaemia, hypotension, hyponatraemia or profound fatigue during immune treatment may indicate endocrine toxicity rather than cachexia alone.
A patient approaching the last days of life who no longer wants food should not be pressured or promised that artificial nutrition will reverse the dying process.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
First-line serial weight and intake historyFirst stepFirst line
Why
Calculate percentage and speed of unintentional loss and document actual calories, protein, fluids and barriers over time.
Interpretation and limitations
Compare with usual dry weight and account for ascites or oedema; more than 5% loss or smaller loss with low BMI or muscle depletion is clinically important.
02
Validated nutrition-risk screening
Why
Use MUST or the locally adopted tool to trigger dietetic assessment and repeat review during treatment and transitions.
Interpretation and limitations
A score organises risk but cannot diagnose cachexia, swallowing safety, body composition or whether artificial nutrition will provide benefit.
03
Dietetic and functional assessment
Why
Evaluate food pattern, energy and protein gap, symptoms, handgrip or sit-to-stand function, food access and realistic goals.
Interpretation and limitations
Match the plan to eating capacity, culture, budget, carer help and treatment; functional decline can identify sarcopenia despite stable fluid-loaded weight.
04
Cause-directed laboratory panel
Why
Assess FBC, renal, liver, calcium, phosphate, magnesium, potassium, glucose, CRP and selected thyroid or cortisol abnormalities.
Interpretation and limitations
Inflammation supports but does not prove cachexia; low phosphate, potassium or magnesium before feeding marks refeeding risk and requires correction with monitoring.
05
Swallowing and gastrointestinal investigation
Why
Use speech-and-language evaluation, endoscopy, CT, contrast study or malabsorption testing when dysphagia, obstruction or diarrhoea changes route.
Interpretation and limitations
Do not place a feeding tube through unassessed obstruction or permit unsafe texture after aspiration signs; choose the least burdensome effective route.
06
Body-composition review
Why
Use CT muscle area at L3, anthropometry or validated bedside measures when sarcopenia will change treatment, rehabilitation or prognosis discussion.
Interpretation and limitations
A normal or high BMI can coexist with severe muscle depletion; interpret single measurements with strength, trajectory, sex and technical method.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Simple starvation or food insecurity

Reduced intake without dominant inflammation preserves a greater adaptive capacity to regain tissue when access, calories and protein are restored safely.

Mechanical or mucosal disease

Dysphagia, gastric outlet or bowel obstruction, mucositis, candidiasis and severe constipation reduce intake through a treatable anatomical or painful barrier.

Endocrine or metabolic disease

Hyperthyroidism, adrenal insufficiency, diabetes, hypercalcaemia, renal failure and immune endocrinopathy cause weight loss and require specific biochemical treatment.

Depression, delirium or dementia

Loss of interest, impaired initiation, altered taste and inability to plan meals can mimic anorexia and require capacity, mood and caregiver assessment.

Infection and organ failure

Sepsis, tuberculosis, heart, liver or lung failure produces inflammatory weight loss, oedema or breathlessness and can coexist with active malignancy.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01Early weight lossScreen, diagnose and remove barriersFirst stepWeight, muscle, intake or function declines during cancer assessment or treatment.

1Calculate loss from usual dry weight, complete validated screening and assess intake, symptoms, swallow, muscle function, inflammation, cancer stage and psychosocial access.
2Treat pain, nausea, mouth disease, constipation, obstruction, infection, endocrine and pancreatic insufficiency and refer dysphagia or high-risk nutrition promptly.
3PreferredBegin dietitian-led fortified preferred food, protein and oral supplement support with tolerable exercise and a defined weight, intake and function review date.

02Route escalationUse the gut when it works and benefit is realisticEscalationOral intake cannot meet needs despite treatment of reversible barriers.

1Clarify the goal, expected duration, gastrointestinal function, aspiration risk, prognosis, treatment intent and patient preference before choosing an invasive route.
2Use enteral tube feeding for a functional accessible gut when swallowing or intake is the limiting step, with placement and refeeding safety planned.
3Consider parenteral nutrition for genuine intestinal failure when expected survival, cancer control, function and home or hospital resources make benefit plausible, then review continuation against complications.

03High refeeding riskReplace vitamins and electrolytes while feeding slowlyNICE high-risk criteria are present before oral, enteral or parenteral nutrition increases.

1Record ECG and fluid status and measure phosphate, potassium, magnesium, glucose and renal function, correcting deficits with pharmacy and dietetic input.
2Give thiamine before and during feeding and start at no more than about 10 kcal/kg/day, or 5 kcal/kg/day in extreme risk, increasing over four to seven days.
3Monitor rhythm, fluid balance, weight, glucose and electrolytes closely and slow or interrupt feed for oedema, arrhythmia, respiratory, neurological or biochemical deterioration.

04Refractory cachexiaShift from targets to comfort without abandoning careCancer is no longer responsive, catabolism is irreversible and artificial nutrition cannot achieve the patient’s goals.

1Explain that reduced appetite is part of disease biology rather than failure by the patient or family and explore what eating and treatment mean to them.
2Offer small desired tastes, mouth care, nausea, pain and dry-mouth treatment and a brief appetite medicine only when a specific short-term goal justifies harm.
3Avoid burdensome tube or parenteral feeding unlikely to improve function or survival and support family through anticipatory guidance and shared end-of-life planning.

Key medicines and prescribing safety3 treatments · regimens, roles and cautions

Prevents acute thiamine depletion, Wernicke encephalopathy and cardiac metabolic failure during carbohydrate reintroduction in a depleted patient.

Thiamine for high refeeding risk

Give oral thiamine 200 to 300 mg daily immediately before and during the first 10 days of feeding, with a balanced multivitamin and intravenous vitamin preparation when the oral route is unavailable.

Do not delay emergency treatment for a laboratory result; replace phosphate, potassium and magnesium concurrently and use intravenous thiamine promptly when encephalopathy or absorption failure is suspected.

Can transiently improve appetite, nausea and sense of wellbeing but does not rebuild muscle or reverse refractory cachexia.

Short-course dexamethasone for appetite

For selected patients with a short prognosis and a clear appetite or wellbeing goal, use dexamethasone 2 to 4 mg orally each morning for a brief trial and stop within one to two weeks if benefit is absent or wanes.

Monitor glucose, infection, delirium, insomnia, proximal weakness, gastrointestinal risk and adrenal suppression; avoid prolonged treatment that worsens the same sarcopenia being treated.

Improves fat, protein and energy absorption after pancreatic cancer, obstruction or resection when maldigestion contributes to weight loss and steatorrhoea.

Pancreatic enzyme replacement

For pancreatic exocrine insufficiency, start at least 50,000 units of lipase with each main meal and 25,000 units with snacks, taken across the food, then titrate to symptoms, weight and dietitian review.

Confirm timing with every meal and snack before increasing, consider acid suppression when response remains poor and investigate bile, infection or obstruction rather than escalating indefinitely.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Treatment intolerance and infection

Low muscle and nutrient reserve increases toxicity, dose interruption, wound failure, immune dysfunction, admission and reduced ability to complete beneficial treatment.

Weakness and loss of independence

Sarcopenia causes falls, pressure injury, impaired cough, fatigue and dependence in washing, shopping, cooking and medication management.

Refeeding syndrome

Rapid nutrition after prolonged depletion can trigger hypophosphataemia, hypokalaemia, hypomagnesaemia, thiamine deficiency, fluid overload, arrhythmia, seizures and respiratory failure.

Artificial-nutrition harm

Feeding tubes and venous nutrition can cause aspiration, infection, thrombosis, metabolic disturbance, fluid overload and burdensome hospital care without reversing refractory cachexia.

Family conflict and moral distress

Equating food with love can generate guilt, coercion and conflict when appetite falls, requiring honest explanation that cachexia is not caused by insufficient effort.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

Measure weight at a meaningful interval using the same conditions and interpret alongside oedema, ascites, intake, muscle function and patient priorities.
Track percentage oral intake, supplement use, swallowing symptoms, stool, pancreatic features, nausea, pain and food access rather than relying on weight alone.
During refeeding, monitor fluid balance, daily weight, glucose, phosphate, potassium and magnesium at protocol frequency and use cardiac monitoring in extreme risk.
For enteral feeding, review tube position and care, aspiration, diarrhoea, blockage, hydration and whether the route still achieves the agreed purpose.
For parenteral nutrition, monitor line infection and thrombosis, liver, glucose, electrolytes, fluid and micronutrients and reassess benefit and exit criteria regularly.
During appetite treatment, define a short review point and record eating pleasure and function as well as glucose, mood, sleep, infection and weakness.
Revisit goals as cancer and function change and document when a comfort-focused approach replaces numerical calorie or weight targets.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

Weight can hide muscle loss

Ascites, oedema and obesity can keep scales stable while skeletal muscle and strength decline substantially during treatment.

Cachexia is not failed feeding

Persistent catabolism explains why relatives cannot reverse the syndrome by persuasion and why blame around uneaten food is harmful.

Nutrition needs a muscle signal

Protein and calories support tissue, but resistance and ordinary functional activity are needed where possible to stimulate muscle synthesis.

The route is not the indication

A central line or feeding tube solves delivery, not inflammatory cachexia; a plausible physiological and patient-centred goal must come first.

Refeeding risk begins with history

Little intake and major weight loss can establish high risk even when the first phosphate result remains within the laboratory range.

Comfort feeding remains active care

Small desired tastes, mouth moisture and removal of pressure can provide pleasure and connection when artificial nutrition offers no recovery.

11Common pitfallsFrequent interpretation and management errors.

01
Calling cachexia simple starvation and promising weight restoration from supplements alone.
02
Using BMI alone and missing sarcopenia in oedema or obesity.
03
Prescribing oral supplements before treating pain, nausea, constipation, candidiasis or pancreatic insufficiency.
04
Allowing unrestricted oral intake despite coughing, wet voice or recurrent aspiration.
05
Starting full-calorie feeding without identifying high refeeding risk and giving thiamine.
06
Replacing phosphate once while ignoring potassium, magnesium, fluid expansion and ongoing insulin shift.
07
Choosing parenteral nutrition because weight is falling despite a functional gut and refractory cachexia.
08
Continuing corticosteroid appetite treatment after brief benefit has disappeared.
09
Interpreting refusal of food at the end of life as neglect or family failure.
10
Setting calorie targets without asking what function, treatment or comfort the patient hopes to gain.