Why do people lose weight when they have cancer?

As an expert in the field of oncology, I can explain that there are several reasons why individuals with cancer may experience weight loss. Cachexia is a significant factor, as it is a complex metabolic disorder that is often associated with chronic illnesses such as cancer. Here's a detailed explanation: 1. Metabolic Changes: Cancer cells can cause significant changes in the body's metabolism, leading to increased energy demands and the breakdown of body tissues, including muscle, for fuel. 2. Altered Nutritional Intake: Patients may have a reduced appetite due to the side effects of treatments like chemotherapy or radiation, or as a result of the cancer itself. This can lead to inadequate caloric intake. 3. Nutrient Malabsorption: Some cancers can affect the gastrointestinal system, leading to malabsorption of nutrients, which contributes to weight loss. 4. Increased Energy Expenditure: The body's energy expenditure can increase as it fights the cancer, and if this is not matched by an increase in food intake, weight loss will occur. 5. Inflammation: Chronic inflammation, which is common in cancer, can also lead to muscle wasting and weight loss. 6. Cancer Treatment Side Effects: Many cancer treatments can cause nausea, vomiting, diarrhea, and other issues that can affect a person's ability to eat and absorb nutrients. 7. Cancer-Related Fatigue: Fatigue is a common symptom of cancer and its treatments, which can make it difficult for patients to prepare or consume food. 8. Psychosocial Factors: The stress and emotional toll of a cancer diagnosis can also impact a person's eating habits and nutritional status. Cachexia is a serious concern because it can lead to a decreased quality of life and a poorer prognosis. It's important for healthcare providers to monitor weight and nutritional status closely and provide appropriate interventions to manage these issues.

Half of all cancer patients suffer from a wasting syndrome called cachexia. Affected patients lose weight, including muscle, no matter how much they eat. The wasting is the immediate cause of about a third of all cancer deaths.