Cachexia: What is it and why does it develop?

Cachexia is a complex metabolic syndrome associated with chronic disease and characterized by unintentional weight loss, primarily from skeletal muscle, with possible concomitant loss of adipose tissue. The classic consensus formulation emphasizes that conventional nutritional support is unable to completely reverse this process, as it is based not only on inadequate food intake but also on profound metabolic shifts. [1]

Cachexia can develop in cancer, chronic heart failure, chronic kidney disease, chronic obstructive pulmonary disease, chronic infections, and a number of inflammatory conditions. A modern review of chronic diseases emphasizes that this is not a strictly oncological problem, but a universal syndrome of exhaustion associated with severe chronic pathology. [2]

In practice, it's especially important to note that cachexia affects more than just weight. Patients also lose strength, endurance, and exercise tolerance, and have a poorer tolerance for surgery, chemotherapy, hospitalization, and infections. In cancer patients, cachexia is associated with poorer treatment tolerance, a higher incidence of complications, and lower survival rates. [3]

The international criteria proposed in the Fearon consensus and confirmed by subsequent guidelines continue to be used for cancer cachexia. Cachexia is defined as a body weight loss of more than 5% over 6 months, or more than 2% with a low body mass index of less than 20 kg per square meter, or in the presence of sarcopenia. This approach is important because it allows for the recognition of the syndrome before extreme debilitation occurs. [4]

In oncology, three stages of the process are also distinguished: pre-cachexia, established cachexia, and refractory cachexia. This is not a formal classification for the sake of classification, but a way to understand where there is still a window for active intervention, and where the priority has already shifted toward symptom control, comfort, and realistic care goals. [5]

Table 1. How cachexia differs from other states of wasting

State	What is the leading mechanism?	What is lost first?	Does simply increasing calories help?
Cachexia	Inflammation, anorexia, catabolism, hormonal and metabolic changes	Skeletal muscle, often also fat	Usually not enough
Starvation	Energy deficiency	First, mainly adipose tissue, then muscle	It helps more often
Sarcopenia	Decreased muscle mass and function, often with age and physical inactivity	Muscles	Strength training, protein, and correction of underlying causes are needed.
Malnutrition	Insufficient intake and absorption of nutrients	Both fat and muscle mass	Often helps if the cause is eliminated

Sources for the table. [6]

Why does cachexia develop?

Cachexia is based on a combination of two major processes: decreased food intake and pathologically increased catabolism. Patients often eat less due to anorexia, nausea, early satiety, pain, dysphagia, depression, or treatment side effects. However, even with partial nutritional support, the body continues to lose muscle mass due to inflammatory and hormonal-metabolic shifts. This is why cachexia cannot be reduced to the formula "eat less, lose weight." [7]

Proinflammatory cytokines, primarily interleukin 1, interleukin 6, and tumor necrosis factor alpha, play a key role. Oncology guidelines and modern reviews describe these mediators as one of the central mechanisms of cachexia because they simultaneously suppress appetite, increase muscle protein breakdown, alter energy metabolism, and support systemic inflammation. [8]

Anabolic resistance develops in parallel. This means that even with sufficient protein and energy intake, muscles respond less well to their usual anabolic stimuli. A review of the molecular mechanisms of cachexia emphasizes that, against this background, proteolysis, autophagy, mitochondrial dysfunction, and oxidative stress are enhanced, while amino acids are more actively redistributed toward tumor and inflammatory processes rather than muscle restoration. [9]

Cachexia is often accompanied by peripheral clinical factors. In cancer, these include tumor intoxication, stomatitis, dysgeusia, nausea, vomiting, diarrhea, pain, obstruction, and treatment side effects. In chronic heart failure, increased work of breathing, intestinal congestion, inflammation, and severe fatigue are also present. In chronic kidney disease, uremia, acidosis, inflammation, and protein-energy depletion are significant. [10]

It's especially important to be aware of conditions that can mimic or exacerbate cachexia. These include hyperthyroidism, poorly controlled diabetes, severe depression, malabsorption, drug-induced weight loss, chronic infections, and severe dysphagia. If such factors are not actively sought, weight loss can be mistakenly considered "inevitable cachexia" and reversible causes may be missed. [11]

Table 2. Common diseases that cause cachexia

Underlying disease	What especially supports exhaustion	Clinical feature
Malignant tumors	Inflammation, tumor factors, anorexia, treatment toxicity	The most studied variant of cachexia
Chronic heart failure	Catabolism, inflammation, low exercise tolerance, intestinal congestion	Associated with increased mortality
Chronic kidney disease	Uremia, acidosis, inflammation, protein-energy depletion	Often overlaps with the concept of protein-energy depletion
Chronic obstructive pulmonary disease	High cost of breathing, hypoxia, inflammation, low mobility	Often accompanied by weakness and shortness of breath
Chronic infections and inflammatory diseases	Constant activation of the immune system	It can develop even with seemingly adequate nutrition.

Sources for the table. [12]

Symptoms and stages

The most noticeable symptom of cachexia is unintentional weight loss. But clinically, the loss of muscle strength and function is even more important. The patient begins to have difficulty getting up from a chair, walking more slowly, tiring more quickly, and having difficulty climbing stairs and performing ordinary daily activities. Sometimes, it is this functional decline that is the first sign, not the number on the scale itself. [13]

Anorexia, early satiety, nausea, taste and olfactory changes, weakness, asthenia, and decreased motivation to move are common. Oncology guidelines explicitly state that patient assessment should include not only body weight and body mass index, but also eating capacity, physical activity, severity of asthenia, and psychosocial distress. [14]

Precachexia is the earliest stage, when systemic inflammation, decreased appetite, early metabolic changes, and weight loss of less than 5% are already present. Early detection and intervention are especially important at this stage, as this is where the likelihood of slowing progression is greatest. [15]

Established cachexia meets the classic diagnostic thresholds: body weight loss of more than 5%, or more than 2% in the presence of a low body mass index or sarcopenia. At this stage, malnutrition, inflammation, functional impairment, and more pronounced muscle weakness are typically present. Intervention is still necessary, but it must be more comprehensive and persistent. [16]

Refractory cachexia is a stage of irreversible catabolism in which the underlying disease progresses rapidly, functional status is poor, and life expectancy is limited. Here, the goal of care shifts from attempts to restore body weight to symptom control, reduction of suffering, family support, and maximizing comfortable nutrition without aggressive and ineffective interventions. [17]

Table 3. Cachexia stages and clinical goals

Stage	Typical signs	The main goal of assistance
Precachexia	Weight loss less than 5%, decreased appetite, early metabolic changes	Early detection and prevention of progression
Cachexia	Weight loss greater than 5%, or greater than 2% in the case of low body mass index or sarcopenia	Stabilization of weight and function, treatment of causes of malnutrition
Refractory cachexia	Irreversible catabolism, poor functional status, limited prognosis	Comfort, symptom control, realistic nutrition goals

Sources for the table. [18]

When urgent help is needed

Urgent assessment is required if weight loss is accompanied by dehydration, severe weakness, orthostatic hypotension, persistent vomiting, or severe diarrhea. In such situations, the risk is not only the depletion itself, but also the rapid development of electrolyte imbalances, acute renal dysfunction, and the inability to maintain even minimal nutrition and fluid intake.

Rapid weight loss accompanied by fever, night sweats, increasing pain, or systemic deterioration is also considered worrisome. This situation requires ruling out an active infection, tumor progression, severe inflammation, or another severe underlying disease that triggered the catabolic cascade.

In patients with heart failure, increasing dyspnea at rest, a sharp decline in exercise tolerance, severe edema, and rapid exhaustion are particularly dangerous. A 2024 meta-analysis showed that cachexia in heart failure is associated with an approximately 1.6-fold increase in overall mortality, so the combination of exhaustion and signs of decompensation requires rapid adjustment of cardiac therapy, not just nutritional support. [19]

In cancer patients, urgent resuscitation is necessary if they are unable to eat due to stomatitis, dysphagia, vomiting, intestinal obstruction, rapid accumulation of ascites, severe pain, and a sharp decline in function. Current oncology and palliative care guidelines emphasize that in such cases, the priority is eliminating symptomatic barriers to eating and drinking, rather than simply prescribing formula or appetite suppressants. [20]

A separate red flag is confusion, drowsiness, falls, and a sharp decline in self-care ability against the background of exhaustion. This picture may reflect severe metabolic disturbances, dehydration, hyponatremia, infection, or terminal worsening of the underlying disease and requires immediate in-person assessment.

Table 4. Red flags for cachexia

Sign	Why is it dangerous?
Persistent vomiting or severe diarrhea	They quickly lead to dehydration and electrolyte disturbances.
Inability to eat and drink	Accelerates catabolism and the risk of hospitalization
Fever and night sweats	Requires exclusion of infection or disease progression
Increasing shortness of breath and edema in heart failure	Decompensation with a high risk of death is possible
Confusion, falls, drowsiness	Severe metabolic disturbances are possible
Intestinal obstruction, severe stomatitis, severe dysphagia	Urgent symptomatic and sometimes invasive measures are needed

Sources for the table.

How is the diagnosis confirmed?

Diagnosis begins not with a single test, but with a systematic assessment of weight, body weight dynamics, body mass index, dietary intake, muscle mass, and function. Oncology guidelines emphasize that screening should be performed regularly, not just when debilitation is already evident, and especially at diagnosis and when treatment is changed. [21]

The key issue is unintentional weight loss. For cancer cachexia, the reference threshold remains greater than 5% over 6 months, or greater than 2% in the case of low body mass index or sarcopenia. However, in practice, kilograms alone are insufficient: in patients with edema, ascites, obesity, or tumor mass, true wasting may be masked. Therefore, assessment must include both body composition and function. [22]

Next, anthropometry, muscle mass, and physical function are assessed. The recommendations list circumferences, weight dynamics, body mass index, instrumental assessment of muscle mass, as well as functional parameters, including asthenia, physical activity, dyspnea, and overall performance. This approach allows us to see not only "how much weight a person has lost" but also "what they can no longer do." [23]

Biochemical parameters can support the diagnosis, but do not alone establish it. Guidelines and reviews most often mention C-reactive protein, albumin, prealbumin, anemia, and other markers of inflammation and catabolism. However, no universal biomarker currently replaces clinical assessment, and laboratory changes can reflect the activity of the underlying disease, dehydration, and inflammation. [24]

A crucial part of diagnosis is identifying factors that reduce nutritional status and can be corrected. It is necessary to determine the presence of pain, stomatitis, dysphagia, constipation, diarrhea, nausea, vomiting, depression, taste disturbances, intestinal obstruction, endocrine causes, malabsorption, and medication side effects. It is this step that transforms the diagnosis of cachexia from a mere observation of thinness into a plan for effective treatment. [25]

Table 5. What really needs to be assessed when cachexia is suspected

Evaluation component	What are they watching?	Why is this necessary?
Weight dynamics	Weight loss in 3 months and 6 months	Basic criteria of the syndrome
Body mass index	Low initial mass reserve	Clarifies diagnostic thresholds
Muscle mass	Instrumental or clinical assessment of sarcopenia	Allows you to identify hidden exhaustion
Function	Strength, endurance, daily activity	Shows clinical severity
Nutrition	How much and how does a person eat, can they swallow, is there early satiety?	Helps find correctable causes
Inflammation and biochemistry	C-reactive protein, albumin, prealbumin, anemia, and others	Complement the clinical picture
Symptoms of the underlying disease	Pain, nausea, diarrhea, constipation, depression, shortness of breath	Without their correction, nutrition will not improve.

Sources for the table. [26]

Treatment

The main principle of cachexia treatment is multimodality. No single measure is considered the gold standard. A modern systematic review from 2025 emphasizes that the complex pathophysiology of cachexia requires a multi-pronged and individualized approach, and the ESMO guidelines explicitly recommend screening, assessment, and multimodal management. [27]

The first step should be correcting the reversible causes of poor nutrition. Pain, nausea, stomatitis, diarrhea, constipation, dysphagia, depression, anxiety, taste disturbances, intestinal obstruction, and other symptoms that interfere with eating should be treated. Oncology guidelines consider this a mandatory part of care, because without addressing symptomatic barriers, even a well-planned diet remains theoretical. [28]

The next basic component is dietary support. Current guidelines consider dietary counseling to be the first step in nutritional support for patients who are still able to eat. For cancer patients, a transition to high-energy and protein-dense foods, enrichment of the usual diet, and oral nutritional formulas are recommended if regular food is insufficient. However, meta-analyses and systematic reviews show that formulas without comprehensive counseling are less effective than support with dietary education. [29]

Tube feeding or parenteral nutrition is not used for everyone, but rather based on individual indications. Guidelines emphasize that the degree of invasiveness should be consistent with the stage of the disease, gastrointestinal function, overall prognosis, and treatment goals. At the end of life, the focus typically shifts from aggressive nutrition to symptom control and comfort, whereas in patients with a life expectancy of more than a few months and mechanical barriers to nutrition, nutritional support may be justified. [30]

Physical activity and exercise are not an afterthought. ESMO recommends moderate, guided exercise as a safe way to maintain and improve muscle mass, and ESPEN emphasizes the benefits of regular activity for aerobic endurance, strength, quality of life, and fatigue reduction. For the most frail patients, this may begin not even with exercise, but with daily walking and physical activity prevention. [31]

Drug therapy is used selectively and is usually not a single-agent solution. Previous guidelines provided insufficient evidence for most drugs, but the 2023 ASCO update now recommends low-dose olanzapine to improve appetite and promote weight gain in some patients with cancer cachexia. If olanzapine is not tolerated, a short course of a progestogen or corticosteroid may be considered. However, the SEOM emphasizes that there is no compelling rationale for routine use of many other agents, including many supplements and anti-inflammatory regimens. Long-term use of corticosteroids is limited by myopathy and other complications, and weight gain with megestrol acetate is primarily due to fat and fluid loss, not skeletal muscle recovery. [32]

Table 6. What modern treatment for cachexia typically consists of

Component	When needed	What does it give?
Treatment of symptoms that interfere with eating	Almost always	Allows you to restore real food consumption
Dietary counseling	The first step for a patient who can eat	Increases energy and protein intake
Oral nutritional mixtures	When regular food is not enough	Helps to get energy and protein
Enteral nutrition	With an intact intestine and the inability to eat enough through the mouth	Bypasses mechanical limitations of the upper sections
Parenteral nutrition	According to strict indications	Used selectively rather than routinely
Physical activity and exercise	According to tolerance and under control	Supports muscle mass and function
Olanzapine	Selectively in oncological cachexia	May improve appetite and weight gain
Progestogens and corticosteroids	Short courses in individual patients	May temporarily improve appetite

Sources for the table. [33]

Prevention and prognosis

The best prevention of cachexia is early screening and intervention at the stage of decreased appetite and the first signs of unintentional weight loss. Guidelines emphasize that regular monitoring of weight, food intake, and functional status should begin at the time of diagnosis and be repeated when treatment changes, rather than being delayed until severe malnutrition occurs. [34]

In oncology, prevention is particularly important for patients with tumors of the pancreas, stomach, lung, esophagus, and upper gastrointestinal tract, where the risk of cachexia is particularly high. According to SEOM, the incidence of the syndrome reaches 20%-40% at diagnosis and 70%-80% in late stages, with pancreatic and gastric tumors having some of the highest rates. This makes nutritional screening part of standard oncology care, rather than an optional extra. [35]

The prognosis is determined not only by the degree of weight loss but also by the underlying disease, the severity of inflammation, the loss of function, and the ability to address the underlying cause of the syndrome. In heart failure, cachexia is associated with a significant increase in overall mortality, while in cancer, it is associated with poorer treatment tolerance, a higher incidence of complications, and decreased survival. The earlier intervention is initiated, the greater the chance of slowing functional decline. [36]

It's important to set realistic goals. In the early stages, you can strive for weight stabilization, improved strength, symptom reduction, and improved treatment tolerance. In later stages, controlling nausea, reducing weakness, reducing distress around food, and maintaining patient and family comfort are often more achievable. This shift in goals does not mean abandoning care, but rather being clinically honest. [37]

FAQ

Is cachexia simply extreme weight loss?
No. It's not just a calorie deficit, but a syndrome involving muscle loss, inflammation, and metabolic changes that aren't resolved by simply increasing food intake. [38]

Can cachexia be cured with a strict diet alone?
Usually not. Nutrition is essential, but without treating the inflammation, symptoms, underlying disease, and functional decline, diet alone is insufficient. [39]

How does cachexia differ from sarcopenia?
Sarcopenia is a syndrome of decreased muscle mass and function, often associated with age and physical inactivity. Cachexia is almost always associated with severe chronic disease and is accompanied by inflammation and catabolism. These conditions can coexist. [40]

When should cachexia be considered in a cancer patient?
When there is unintentional weight loss, decreased appetite, weakness, decreased treatment tolerance, or early signs of functional decline. Particular vigilance is needed for tumors of the pancreas, stomach, and lung. [41]

What are the primary criteria for diagnosis?
Most commonly, a body weight loss of more than 5% over 6 months is considered, or more than 2% with a low body mass index of less than 20 kg per square meter or with sarcopenia. [42]

What tests confirm cachexia?
No single test alone confirms it. Laboratory markers of inflammation and nutritional status are helpful, but the diagnosis remains clinical and relies on weight dynamics, muscle mass, function, and the underlying disease. [43]

Is exercise necessary if a person is already exhausted?
Yes, but only as tolerated and under supervision. Moderate activity and exercise help maintain muscle mass and function, while complete inactivity usually accelerates strength loss. [44]

Are there any medications that actually help?
Some cancer patients may benefit from low doses of olanzapine to improve appetite and gain weight. Some patients are considering short courses of progestogens or corticosteroids, but there is no universally effective treatment yet. [45]

When is tube or intravenous feeding truly justified?
When regular nutrition is impossible or clearly insufficient, and the prognosis and treatment goals make such support reasonable. This decision is always made individually, taking into account gastrointestinal function and the stage of the disease. [46]

Does cachexia always indicate terminal disease?
No. Refractory cachexia is indeed more often associated with later stages of the disease, but precachexia and established cachexia can be recognized earlier, and early intervention offers the best chance of slowing progression. [47]