Malnutrition in adults: under-recognised and manageable in general practice

Malnutrition — the state of deficient nutrition producing measurable loss of body mass and function — is one of the most prevalent and under-identified diagnoses in Australian clinical practice. It is not confined to people who look thin: sarcopenic obesity (low muscle mass with high body fat) and cancer cachexia can occur at any BMI. The general practitioner, present at routine chronic-disease reviews, preventive health checks, and 75+ assessments, is best placed to detect it early.

This article covers how malnutrition presents in adult general practice, how to screen and diagnose it, what to do first, and when to refer.

A. Core clinical — the AU general-practice framework

Prevalence in Australian clinical settings

The gap between prevalence and recognition is large. ESPEN 2022 geriatric nutrition guidelines and AIHW data estimate:

• Community-dwelling older adults: 5–10% malnourished; 30–50% of frail or recently hospitalised older adults at nutritional risk.
• Residential aged care: 40–70% — the highest-risk clinical setting in Australian general practice.
• Cancer outpatients: 20–40% overall; 60–80% in upper gastrointestinal and head-and-neck cancers.
• Hospitalised patients: approximately 30% on admission, with nutritional status frequently deteriorating further during the admission.
• Sarcopenia prevalence rises from approximately 5% at age 60 to 50% at age 85 or above.

Weight loss in older adults is common but never inherently normal. Every case of unintentional weight loss warrants investigation.

GLIM 2019 criteria — how to diagnose malnutrition

The Global Leadership Initiative on Malnutrition (GLIM 2019) criteria (Cederholm Clin Nutr 2019) require at least one phenotypic criterion plus at least one aetiologic criterion:

Phenotypic criteria (need ≥1):

• Unintentional weight loss >5% in ≤6 months, or >10% beyond 6 months.
• Low BMI: <20 kg/m² if aged under 70 years; <22 kg/m² if aged 70 or over.
• Reduced muscle mass (measured by calf circumference, DEXA, bioimpedance, or hand-grip strength).

Aetiologic criteria (need ≥1):

• Reduced food intake or absorption: eating ≤50% of estimated requirements for >1 week, or any reduction for >2 weeks, or a GI absorptive disorder (coeliac disease, inflammatory bowel disease, pancreatic insufficiency).
• Disease burden or inflammation: any acute disease, or a chronic condition with active inflammation.

Severity grading:

• Moderate: 5–10% weight loss in <6 months, or BMI 18.5–20 if <70 years (20–22 if ≥70), or mild-to-moderate muscle mass loss.
• Severe: >10% weight loss in <6 months, or BMI <18.5 if <70 years (<20 if ≥70), or severe muscle mass loss.

Screening tools — use these at every relevant visit

RACGP Silver Book recommends nutritional screening at aged-care, chronic-disease, and preventive health consultations.

For adults aged 65 and over (community-dwelling): use the Mini Nutritional Assessment Short Form (MNA-SF) — 6 items, 5 minutes; a score of 11 or below identifies those at nutritional risk and triggers the full 18-item MNA assessment. Sensitivity ~94% in older adults.

For working-age adults and hospital inpatients: use MUST (Malnutrition Universal Screening Tool) — 5 items assessing BMI, recent weight loss, and acute-disease effect; available as a free download (BAPEN).

Practical bedside screens:

• Always weigh, calculate BMI, and ask about weight trajectory at every chronic-disease review.
• Ask whether the patient’s clothes are fitting differently, or whether they have noticed weight loss without trying over the past six months.
• Hand-grip strength with a dynamometer — where available, the strongest single functional predictor of sarcopenia and malnutrition outcomes.
• Calf circumference below 31 cm in an older adult suggests low muscle mass even at a normal BMI.

Causes and contributing factors in general practice

Taking a systematic approach to aetiology directs effective management:

• Medication-induced appetite suppression: SSRIs (dry mouth, nausea), GLP-1 receptor agonists (semaglutide, tirzepatide — significant weight loss is the mechanism), metformin (GI side effects), opioids, anticholinergics, digoxin, chemotherapy, immunotherapy.
• Dental problems: missing teeth, ill-fitting dentures, periodontal pain — addressed via the GP oral health pathway and Medicare-funded dental referral schemes in some states.
• Swallowing difficulties (dysphagia): post-stroke, Parkinson’s disease, motor neuron disease, oesophageal stricture — warrants speech pathology referral.
• Mental health: depression is the most common reversible cause of appetite loss in older adults; dementia causes progressive disinterest in food and inability to self-feed.
• Chronic disease: cancer cachexia, COPD, chronic heart failure, chronic kidney disease, and inflammatory bowel disease all drive disease-related malnutrition through inflammation and catabolism.
• Social factors: living alone, food insecurity, limited cooking ability, poor mobility preventing shopping, recent bereavement, low income.
• Malabsorption: coeliac disease, pancreatic insufficiency, bacterial overgrowth — screen with tissue transglutaminase IgA, faecal elastase, and faecal calprotectin where clinically indicated.

Investigations

Baseline blood panel: FBC; UEC, eGFR (urea-creatinine ratio elevation reflects catabolism); LFTs (albumin — low specificity for malnutrition but reflects inflammatory state and tracks response); calcium, magnesium, phosphate (refeeding risk markers); TSH; B12, folate, ferritin; vitamin D; HbA1c; CRP and ESR (inflammation signal — the GLIM aetiologic “disease burden” criterion). Add faecal elastase, TTG-IgA, and faecal calprotectin if malabsorption is suspected. Consider age-appropriate cancer screening with blood tests (PSA, CA-125, CEA, FBC) for unexplained weight loss with elevated ESR in adults over 50.

B. Food-first management

The evidence for food-first

Cochrane review — Milne 2009 (CD003288) — the most-cited meta-analysis on oral nutritional supplementation — showed that protein-energy supplementation in malnourished older adults reduces all-cause mortality by approximately 21% (relative risk 0.79), reduces complication rates, and improves weight and grip strength compared with usual care. Oral nutritional supplement (ONS) drinks were the primary intervention.

Practical food-first strategies:

• Small, frequent meals: 5–6 small servings throughout the day rather than three large meals.
• Energy-dense additions at every opportunity: cream in soup, butter on bread, milk powder added to hot drinks, peanut butter on toast, full-cream yoghurt, avocado, cheese, eggs, nuts.
• Protein at every meal: aim for 25–30 g of protein per meal. Good sources: eggs, tinned fish, meat, full-cream dairy, legumes, tofu.
• Avoid filling up on low-energy bulky foods (plain cereal with skim milk, clear broths, raw vegetables without protein or fat) at the expense of energy-dense options.
• Reduce fluid intake immediately before and during meals to avoid early satiety from fluid.

Protein requirements

Per PROT-AGE consensus (Bauer JAMDA 2013), the protein requirement for healthy older adults is 1.0–1.2 g/kg/day (substantially above the 0.8 g/kg/day general population RDA). In disease states — active cancer, wound healing, inflammatory conditions, post-surgery — this rises to 1.2–1.5 g/kg/day. Most older Australians living with chronic disease are not meeting these targets.

Oral nutritional supplements

When food fortification alone is insufficient, oral nutritional supplement drinks (Sustagen, Ensure, Fortisip, Resource, Fresubin) add 300–600 kcal and 12–24 g protein per serve. Critical practical point: serve ONS drinks between meals, not with meals — given with meals they replace food rather than supplement it, reducing overall intake. Refrigerating them and serving in a small glass (rather than a full bottle) improves acceptability. ONS drinks are not PBS-listed; they are purchased privately (approximately $3–5 per serve). DVA and some aged-care pharmacy supply schemes cover some products for eligible patients.

Resistance exercise

Protein without exercise does not maximally stimulate muscle protein synthesis in older adults. Progressive resistance exercise two to three times weekly — chair exercises, resistance bands, weights, or a supervised gym programme — combined with adequate protein intake is the most evidence-based approach to sarcopenia management. The LIFE study (NEJM 2014) confirmed that structured physical activity in older adults at risk of mobility disability significantly reduced major mobility disability over 2.6 years.

C. Refeeding syndrome — recognise and prevent

What it is and why it matters

Refeeding syndrome is a potentially fatal metabolic complication of rapid nutritional repletion after severe or prolonged undernutrition. The mechanism: starvation depletes intracellular potassium, magnesium, and phosphate, and thiamine — the cofactor for carbohydrate metabolism. When carbohydrates are reintroduced and insulin rises, these ions shift rapidly from the bloodstream back into cells, causing severe extracellular deficiencies that affect cardiac muscle, respiratory muscles, and nerve tissue.

NICE CG32 (nutrition support for adults) identifies high-risk criteria for refeeding syndrome — if any one of the following applies, hospital-level refeeding management is required:

• BMI below 16 kg/m².
• Unintentional weight loss of more than 15% in the past 3–6 months.
• Little or no nutritional intake for more than 10 days.
• Pre-feed low blood levels of potassium, magnesium, or phosphate.

Or if two or more of the following apply:

• BMI below 18.5 kg/m².
• Unintentional weight loss of more than 10% in 3–6 months.
• Little or no nutritional intake for more than 5 days.
• History of alcohol dependence, insulin use, chemotherapy, antacid use, or diuretics.

Management of high-risk patients

Therapeutic Guidelines (eTG) and NICE CG32 both recommend:

• Inpatient setting for refeeding initiation in high-risk patients.
• Thiamine 200–300 mg orally or IV before the first feed, continued daily for seven days. In patients with suspected Wernicke encephalopathy (confusion, ataxia, ophthalmoplegia — particularly in chronic alcohol use or severe anorexia nervosa) give IV thiamine 500 mg three times daily for two to three days before any glucose. Never give IV glucose before thiamine in alcohol use disorder — doing so can precipitate or worsen Wernicke encephalopathy.
• Start feeds at ≤10 kcal/kg/day, increasing gradually over 5–7 days to full requirements.
• Daily electrolyte monitoring (potassium, magnesium, phosphate) for at least the first seven days; correct deficiencies during refeeding, not before.
• Cardiac monitoring if BMI is below 12 or electrolyte disturbance is severe.

D. Australian operations

MBS items

Standard consultation items 23, 36, and 44 apply. The GP Management Plan and Team Care Arrangement (GPCCMP) items 965 and 967 fund chronic disease management and provide up to five allied health visits per calendar year (combined across all allied health disciplines). Malnutrition in the context of a chronic disease qualifies.

Key allied health items:

• Dietitian item 10954 — Medicare subsidy under GPCCMP.
• Speech pathology item 10970 — for dysphagia assessment and management.
• 75+ Health Assessment items 701–707 — structured opportunity to weigh, screen for malnutrition using MNA-SF, and initiate referrals.
• ATSI Health Assessment item 715.
• For active eating disorder: Eating Disorder Management Plan items 90250/90251 with up to 40 psychological therapy sessions.

Community support pathways

• My Aged Care (1800 200 422): Home Care Package can fund Meals on Wheels, in-home meal preparation assistance, and community dietitian services. Assessment via the Aged Care Assessment Team (ACAT/ACAS) for a Home Care Package at the appropriate level.
• Meals on Wheels Australia: subsidised meal delivery for older adults; initiated by GP referral or through My Aged Care.
• Community health centre dietitians: bulk-billed in some states and territories; contact state community health services.

PBS

Thiamine (vitamin B1) and B-complex vitamins are PBS-listed on the general schedule. Cholecalciferol (vitamin D) is PBS-listed for documented deficiency. Iron salts (ferrous sulphate, ferrous fumarate) are general schedule. Most ONS drinks are not PBS-listed — they are purchased privately or through DVA Pharmaceutical Benefits Scheme for eligible veterans. Intravascular iron (ferric carboxymaltose, Ferinject) is PBS Authority Required for certain indications including confirmed iron deficiency where oral iron is ineffective or intolerable.

E. Special populations

Residential aged care. Malnutrition is near-universal in residential aged care — affecting 40–70% of residents — yet remains poorly documented and treated. Every GP visiting a residential aged care facility should integrate routine weight recording, MNA-SF screening, and dietitian engagement into their care framework. The Royal Australian College of General Practitioners’ Silver Book and the RACGP aged care resources provide evidence-based guidance for this setting.

Cancer patients. Malnutrition in cancer — often called cachexia when inflammatory — is characterised by involuntary weight loss, muscle wasting, and systemic inflammation that does not fully respond to conventional nutritional support because the underlying tumour drives catabolism. Early dietitian involvement at cancer diagnosis, not waiting for obvious weight loss, is best practice per Cancer Australia and ESPEN. GPs co-managing cancer patients should integrate nutritional status into each shared-care review and initiate GPCCMP referral to a dietitian promptly.

Eating disorders. Active anorexia nervosa, bulimia nervosa, and avoidant-restrictive food intake disorder require a dedicated eating disorder management pathway — not standard malnutrition management. The MBS Eating Disorder Management Plan (items 90250/90251) provides up to 40 psychological therapy sessions. GPs should NOT attempt rapid nutritional repletion in severe anorexia nervosa outside a specialist setting; refeeding syndrome risk is high and potentially fatal. Contact a specialist eating disorder service (statewide services listed via the National Eating Disorders Collaboration at nedc.com.au).

Post-hospital discharge. The 60-day post-hospital discharge window is a high-risk period for nutritional deterioration and readmission. A post-discharge GP review at 2 weeks should include weight measurement, nutritional screening, medication review, and dietitian referral if not already in place.

First Nations Australians. Food security is a critical issue in many First Nations communities, particularly in remote and regional areas, making malnutrition a significant concern. The ATSI Health Assessment (item 715) provides a structured opportunity for nutritional screening. Culturally appropriate food support (including traditional foods) should be incorporated into dietary advice where relevant.

When to escalate

• Suspected Wernicke encephalopathy (confusion, ataxia, ophthalmoplegia, particularly in chronic alcohol use or severe restrictive eating) — same-day emergency department; IV thiamine before any glucose.
• Active eating disorder with medical instability (pulse below 50, systolic blood pressure below 90, severe electrolyte abnormality, BMI below 13) — same-day emergency department assessment.
• Severe hypophosphataemia, hypokalaemia, or hypomagnesaemia in a patient at refeeding risk — emergency department; do not commence oral or enteral nutrition without electrolyte correction and monitoring.
• BMI below 14 with any clinical instability — hospital admission for supervised refeeding.
• Dysphagia causing aspiration pneumonia risk — urgent speech pathology review; consider hospital admission.
• Unexplained weight loss with elevated CRP and ESR in an adult over 50 — urgent malignancy workup.
• Malnutrition not responding to community food-first + dietitian management at 4–6 weeks — consider geriatrician or gastroenterology review; enteral nutrition may be needed.

What this article is and is not

This is general health information based on current Australian and international guidelines — Therapeutic Guidelines (eTG), RACGP Silver Book, Dietitians Australia position statement, NICE CG32, and GLIM 2019 — written for patients and carers who want to understand malnutrition and what general practitioners do about it in Australia. It is not personal medical advice and does not substitute for assessment by your own GP or dietitian.

For Australian support: HealthDirect — malnutrition, Better Health Channel — nutrition, My Aged Care 1800 200 422.

For mental health support: Lifeline 13 11 14, Beyond Blue 1300 22 4636, 13YARN 13 92 76.

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Sources cited

1. Therapeutic Guidelines (eTG) — Nutrition and refeeding syndrome
2. RACGP Silver Book — Nutrition and hydration in aged care
3. Australian Medicines Handbook (AMH)
4. Dietitians Australia — malnutrition position statement
5. My Aged Care
6. HealthDirect — malnutrition
7. Better Health Channel — nutrition for older adults
8. MBS Online — dietitian item 10954
9. MBS Online — 75+ health assessment items 701–707
10. ESPEN 2022 — Clinical nutrition and hydration in geriatrics
11. NICE CG32 — Nutrition support for adults (2017)
12. Cederholm T et al. — GLIM 2019 malnutrition criteria (Clin Nutr 2019)
13. Milne AC et al. — Protein and energy supplementation in elderly people — Cochrane 2009
14. Bauer J et al. — PROT-AGE protein requirements — JAMDA 2013