The cachexia anorexia syndrome is a complex metabolic syndrome of involuntary weight loss associated with cancer and some other palliative conditions a consensus definition of cachexia related to either cancer or chronic disease has been proposed, namely: weight loss with or without fat loss, and additional criteria (three required for diagnosis)
- decreased muscle strength,
- reduced muscle mass,
- anorexia, or
- biochemical alterations [anemia, inflammation, and low albumin]. 
A systematic review of the literature on cachexia suggests that there are a range of pathways involved and that the interactions between weight loss, nutritional intake and anorexia are not straightforward or predictable. 
Assessment and management of cachexia should identify and treat according to the stage (pre-cachexia, cachexia, refractory cachexia),and seek to treat potentially reversible factors (secondary nutritional impact symptoms - S-NIS).  Nutritional assessment tools that include markers of inflammation have been investigated.  Their role in clinical practice may be to identify patients earlier in the palliative trajectory, and be incorporated into clinical practice guidelines about management of the syndrome. 
What is known
The detailed neurophysiology of appetite / anorexia is not well understood in humans. It may be different from the mechanism of cachexia / weight loss.  Genetic polymorphisms are being studied and show promise in the identification of susceptibility biomarkers. 
The metabolic profile of cancer cachexia is not the same as that of starvation, which is defined as secondary cachexia. Cancer cachexia involves inflammation, hypermetabolism, neuro-hormonal changes, and the production of proteolytic and lipolytic factors. [1,7] Raised CRP is well-establised as a marker in cachexia. 
Appetite loss occurs in over half of all palliative care patients, and weight loss becomes more common in the last weeks and months of life. 
Loss of weight and loss of appetite do not always occur together. Some patients have cachexia despite maintaining a relatively normal appetite and nutritional intake. 
Cachexia has an impact on performance state.  Loss of weight and appetite due to cancer progression have prognostic relevance for symptom burden, performance state, survival, and the ability to tolerate palliative chemotherapy. 
Cachexia may also be a prognostic factor in non-malignant conditions. 
There is little strong evidence to support the provision of nutritional advice for weight-losing patients.  Two approaches have been identified, the first involving strategies to maximise intake, and the second focusing on allowing the patient to ‘eat what they like’. Further evidence is needed to understand whether and at what stage specific subgroups may benefit from more intensive nutritional support.
What it means in practice
- Appetite is a subjective symptom. Simple assessment tools are available, such as the Symptom Assessment Scale, which is part of the PCOC dataset.
- A simple and valid nutrition assessment tool used in research and practice is the Patient Generated Subjective Global Assessment, which has been recommended for patients with cancer cachexia. 
- Eating and food have great social, cultural and psychological significance for patients and their families, and issues relating to nutritional support are often socially and ethically complex. [12-14] The goals of nutritional support are both physical and psychosocial. 
- If an underlying malignancy can be effectively treated, this may reverse the cachexia anorexia syndrome.
- In patients who have advanced dementia, loss of appetite and decreasing oral intake may be a marker of the transition to end-stage disease, although contributing factors should be sought and addressed as appropriate. Families of patients with end-stage dementia may require increased support as they deal with this change.