Unintentional Weight Loss, Sarcopenia, and Cachexia

Definition and Diagnosis

Unintentional weight loss is a general term describing any involuntary decrease in body weight that may involve loss of fat, muscle, or both 1
Sarcopenia is specifically defined as low lean body mass (primarily muscle) with associated fatigue, decreased strength, and limited physical function 1, 2
Cachexia is a complex metabolic syndrome characterized by involuntary weight loss with ongoing loss of skeletal muscle mass with or without fat loss 1, 3, 4

Sarcopenia can be primary (age-related) or secondary (disease-related) 4, 5
Cachexia is associated with underlying illnesses such as cancer, chronic heart failure, COPD, inflammatory bowel disease, and chronic kidney disease 4, 6

The presence of sarcopenia and/or cachexia is associated with poorer clinical outcomes, including increased mortality, treatment complications, and reduced quality of life 7, 2
In cancer patients, sarcopenia is associated with higher incidence of chemotherapy-related toxicity, shorter time to tumor progression, and reduced survival 7

Appendicular skeletal muscle mass index below defined thresholds (<5.5 kg/m² in women or <7.2 kg/m² in men) is used in diagnosis of sarcopenia 4
Diagnostic criteria for cachexia include weight loss >5% alone, or weight loss >2% if BMI is <20 kg/m² or if there is reduced muscle mass 4, 5

Cachexia affects 10-15% of patients with chronic heart failure and is associated with poor outcomes, according to the European Society of Cardiology 8
Cachexia involves generalized loss across all body compartments, including lean tissue, fat tissue, and bone tissue, making traditional signs of dehydration harder to distinguish, as noted by the European Society of Cardiology 8
Clear subcutaneous veins can be visible in cachectic patients regardless of hydration status due to loss of subcutaneous fat, as reported by the European Society of Cardiology 8

Atrophied muscles are a characteristic of cachexia itself rather than a specific indicator of dehydration, as stated by the European Society of Cardiology 8
Clear subcutaneous veins are not a reliable indicator of dehydration in cachectic patients due to loss of subcutaneous fat, according to the European Society of Cardiology 8
Bony prominences are a characteristic feature of cachexia itself due to loss across all body compartments, making them poor indicators of hydration status, as noted by the European Society of Cardiology 8