Cachexia

Cachexia (/kəˈkɛksiə/ ^ⓘ) is a syndrome that happens when people have certain illnesses, causing muscle loss that cannot be fully reversed with improved nutrition. It is most common in diseases like cancer, congestive heart failure, chronic obstructive pulmonary disease, chronic kidney disease, and AIDS. These conditions change how the body handles inflammation, metabolism, and brain signaling, leading to muscle loss and other harmful changes to body composition over time. Unlike weight loss from not eating enough, cachexia mainly affects muscle and can happen with or without fat loss. Diagnosis of cachexia is difficult because there are no clear guidelines, and its occurrence varies from one affected person to the next.

Like malnutrition, cachexia can lead to worse health outcomes and lower quality of life.

Cachexia is hard to define because it often happens alongside malnutrition and sarcopenia. Since there are no clear rules separating these conditions, experts continue working to agree on definitions to help treat these nutrition-related problems.

In the past, cachexia was described as "a complex metabolic syndrome associated with underlying illness and characterized by loss of muscle with or without loss of fat mass." In 2011, experts updated this definition, saying cachexia is "a multifactorial 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 and leads to progressive functional impairment." They also suggested breaking it into three stages: pre-cachexia, cachexia, and refractory cachexia.

Cachexia and malnutrition are related but not the same. Malnutrition happens when the body doesn't get enough nutrients, leading to changes in body weight, physical strength, and mental function. Malnutrition includes both disease-related malnutrition as well as malnutrition without disease such as seen in starvation or aging. Cachexia should be viewed as a type of malnutrition in which inflammation from a long-term illness causes unwanted muscle loss.

Cachexia and sarcopenia are similar because both cause weight and muscle loss, along with symptoms like weakness and loss of appetite. The difference is sarcopenia is caused by aging, while cachexia happens due to long-term disease and inflammation.

Cachexia is most commonly associated with end-stage cancer, often called cancer cachexia.

Other conditions that frequently cause cachexia include: