Cachexia and Weight Loss
Cachexia is weight loss driven by inflammation and underlying disease rather than by eating too little; it cannot be reversed by food alone and needs medical and dietetic assessment rather than a stricter diet.
Plain English
Patient-Friendly Explanation
Cachexia is a pattern of weight loss caused by an underlying illness rather than by eating too little. It occurs most often in advanced cancer, and also in heart failure, kidney disease, chronic lung disease and advanced liver disease. What makes it different from ordinary dieting is what is lost and why. In cachexia the body breaks down muscle even when there is enough food available, because inflammatory signals from the disease override the normal signals that would protect muscle. The result is a progressive loss of muscle, sometimes with loss of fat as well, together with fatigue, loss of appetite, early fullness and weakness. Doctors describe it using agreed criteria: unintentional weight loss of more than five per cent of body weight over six months, or a body mass index below twenty with any further loss, or a loss of more than two per cent when muscle mass is already low. It is common. Around half to eighty per cent of people with cancer develop it, it is frequent in cancers of the pancreas, stomach and oesophagus, and it is estimated to account for about one in five cancer deaths. Two misunderstandings cause harm. The first is that cachexia is simply starvation and will respond to more calories; it does not, because the problem is not only intake. The second is that obesity protects against it. It does not. A person carrying extra weight can lose a great deal of muscle while the scales barely move, which is why unintentional weight loss, especially with reduced appetite and strength, is always a reason to see a doctor rather than a cause for congratulation. In a weight clinic this distinction matters most in people who are losing weight faster than intended on a reduced diet, or after bariatric surgery when intake is poor, or when weight loss is accompanied by new fatigue or loss of appetite.
Medical
Clinical Definition
Cachexia is a multifactorial metabolic syndrome defined by an ongoing loss of skeletal muscle mass, with or without loss of fat mass, that cannot be fully reversed by conventional nutritional support. The widely used operational definitions are those of Evans and colleagues in 2008 and Fearon and colleagues in 2011. The 2011 consensus requires weight loss of more than 5 per cent over the previous six months in the absence of simple starvation, or a body mass index below 20 kg/m2 with any degree of loss greater than 2 per cent, or an appendicular skeletal muscle index consistent with sarcopenia with loss greater than 2 per cent; the 2008 definition used loss of at least 5 per cent over 12 months plus three of five criteria - reduced muscle strength, fatigue, anorexia, low fat-free mass index and abnormal biochemistry (C-reactive protein above 5 mg/L, interleukin-6 above 4 pg/mL, haemoglobin below 12 g/dL, albumin below 3.2 g/dL). It is staged as pre-cachexia, cachexia and refractory cachexia. Prevalence is 50 to 80 per cent among patients with cancer and reaches 60 to 70 per cent in gastro-oesophageal and pancreatic cancer, with the syndrome implicated in approximately 20 per cent of cancer deaths; cardiac cachexia affects 16 to 34 per cent of patients with advanced heart failure, using a threshold of at least 6 per cent non-oedematous loss over 6 to 12 months. The pathophysiology differs fundamentally from starvation. Tumour and host-derived pro-inflammatory cytokines - tumour necrosis factor-alpha, interleukin-1beta, interleukin-6 and interferon-gamma - activate the ubiquitin-proteasome pathway through FOXO transcription factors and the muscle-specific E3 ligases MuRF1 and atrogin-1, suppress MyoD through nuclear factor kappa B, and reduce IGF-1 signalling and protein synthesis; lipid-mobilising factor and zinc-alpha-2 glycoprotein drive lipolysis. Resting energy expenditure is typically 10 to 15 per cent above predicted values despite weight loss, appetite signalling is blunted with hypothalamic resistance to ghrelin and leptin, and zinc depletion contributes to taste disturbance and anorexia. Prognostically, a loss of 2.5 kg over 6 to 8 weeks is enough to worsen performance status, and death is typically associated with around 30 per cent weight loss. Management is multimodal and the underlying disease remains the primary target: dietitian-led nutrition support, resistance exercise where tolerated, treatment of the inflammatory condition, and selective use of appetite stimulants such as progestogens or corticosteroids, whose benefit is limited and temporary. Body weight alone underestimates the problem in people with obesity, in whom body composition assessment is needed to detect loss of lean mass, and cachexia should be considered whenever weight is falling without an intended energy deficit.
Key Insight
Why It Matters
Losing weight quickly without trying is a symptom, not a success: cachexia means the body is breaking down muscle despite available food, so it calls for diagnosis and nutrition support rather than a stricter diet.
Sources
Reviewed against standard medical references.
Medically reviewed by
Family Physician & Registered Acupuncturist, Accord Medical Clinic. MBBS (NUS), Graduate Diploma in Family Medicine (NUS), Graduate Diploma in Acupuncture (Singapore College of TCM).
Last reviewed: October 2026
This page is general health education, not medical advice. Whether any treatment is appropriate for you is a decision made in consultation after assessment.
