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  experience weight loss and cachexia, or wasting, which is the combination of weight loss and muscle mass loss. Weight loss and muscle wasting also often come 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 be from other side effects of cancer or cancer treatment that include:
- Changes to the immune system or metabolism, which is 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 effects—also called symptom management, palliative care , or supportive care—is 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 your comfort and well-being. The following suggestions may help:
- Increase the amount of food you eat. Talk with your health care team about how much more you should try to eat.
- 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 shortly before each cancer treatment, such as chemotherapy, to help prevent feelings of dislike to these foods due to nausea or vomiting from treatment.
Nutrients given through an intravenous (IV) tube, which is a tube inserted into a vein, are usually not recommended, except when a person is expected to recover and requires short-term nutritional support.
Sometimes, 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 feeling full before eating enough food.
- Pancreatic enzyme (lipase) replacement helps the body absorb fat.
- Dronabinol (Marinol), a cannabinoid made in the laboratory, may stimulate appetite.
- Other medications are being studied to help people with cancer improve their appetite and gain weight.
Nutrition counseling may help people with cancer get essential nutrients, such as protein, vitamins, and minerals into their diet and maintain a healthy body weight. Ask your health care team for a referral to a registered dietitian or nutritionist. You can also find a dietitian  through the Academy of Nutrition and Dietetics.
You may also find it helpful to keep a record of what, when, and how much you ate, including how you felt during and afterwards. For example, did you have nausea, feel full quickly, or notice changes in how you taste the food. These details can help you work with your health care team to find the best way to maintain your weight, or gain needed weight, during cancer treatment.
Side Effects