Weight loss is common among people with cancer and is often the first noticeable sign of the disease. As many as 40% of people with cancer report unexplained weight loss at the time of diagnosis, and up to 80% of people with advanced cancer  (cancer that cannot be cured) experience weight loss and cachexia (or wasting), which is the combination of weight loss and muscle mass loss. It is common for people with solid tumor cancers (such as lung and breast cancers) and people with blood cancers (such as leukemia and lymphoma) to experience weight loss.
The condition is associated with fatigue , weakness, loss of energy, and an inability to perform everyday tasks. People experiencing cachexia often cannot manage treatments well and may experience more intense symptoms.
Weight loss often begins when a person experiences appetite loss  or finds food unappealing. This may result from other side effects of cancer or cancer treatment that include:
- Changes to the immune system or metabolism (the process of the body breaking down food and turning it into energy)
- Nausea and vomiting 
- Constipation 
- Mouth sores 
- Difficulty swallowing 
- Loss of taste 
- Depression 
- Pain 
Relieving side effectsâalso called symptom management, palliative care , or supportive careâis an important part of cancer care and treatment. Talk with your health care team about any symptoms you experience, including any new symptoms or a change in symptoms.
Controlling cancer-related weight loss is important for the comfort and well-being of a person with cancer. The following suggestions may help:
- Increase the amount of food you eat by about 450 calories per day.
- Consider asking your doctor about receiving food through a tube that goes directly to the stomach, which may help people with head and neck or esophageal cancers who are having difficulty chewing  or difficulty swallowing .
- Eat light meals and avoid protein-rich foods before cancer treatment to help prevent aversions (feelings of dislike) to these foods.
Nutrients given through an intravenous (IV) tube (a tube inserted into a vein) are usually not recommended, except when a person is expected to recover and requires short-term nutritional support.
In some cases, doctors may recommend medications to address weight loss.
- Megestrol acetate (Megace) is a progesterone hormone that can improve appetite, weight gain, and a person's sense of well-being.
- Steroid medications can increase appetite, improve a person's sense of well-being, and help with nausea, weakness, or pain. Because of serious side effects, do not use steroids for more than a few weeks.
- Metoclopramide (Reglan) can prevent early satiety (feeling full before eating enough food).
- Pancreatic enzyme (lipase) replacement helps the body absorb fat.