Why do people lose weight when they have cancer?

As an expert in the field of oncology, I can explain the reasons behind weight loss in cancer patients. Weight loss is a common symptom experienced by many individuals with cancer. There are several factors that contribute to this weight loss: 1. Increased Metabolic Demand: Cancer cells often have a higher metabolic rate than normal cells. This means they consume more energy, which can lead to the body's energy stores being depleted, resulting in weight loss. 2. Altered Energy Utilization: Cancer cells may also alter the way the body processes and utilizes nutrients from food. This can make it difficult for the body to derive the necessary energy from the food consumed, leading to a negative energy balance and subsequent weight loss. 3. Inflammation: The body's response to cancer can include inflammation, which can increase metabolic rate and contribute to weight loss. 4. Anorexia and Cachexia: Many cancer patients experience a loss of appetite (anorexia) and a complex metabolic disorder associated with cancer called cachexia, which can cause severe weight loss and muscle wasting. 5. Treatment Side Effects: Cancer treatments, such as chemotherapy and radiation, can cause side effects like nausea, vomiting, and changes in taste, which can reduce a patient's ability to eat and maintain a healthy weight. 6. Stress and Anxiety: The psychological impact of a cancer diagnosis can lead to decreased appetite and increased stress, both of which can contribute to weight loss. 7. Malabsorption: In some cases, the cancer itself or its treatment may interfere with the body's ability to absorb nutrients properly, leading to malnutrition and weight loss. Weight loss in cancer patients is a complex issue that can be multifactorial, involving both the disease itself and the body's response to it, as well as the treatments employed to fight the disease.

This pressure causes some of the signs and symptoms of cancer. ... A cancer may also cause symptoms like fever, extreme tiredness (fatigue), or weight loss. This may be because cancer cells use up much of the body's energy supply, or they may release substances that change the way the body makes energy from food.