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Weight Loss and Cancer

Cancer patients often struggle with weight loss, which can happen during treatment for a number of reasons. Weight loss or gain may be used as a tool to monitor a patient’s success during treatment. Maintaining weight is important because treatment is difficult on the body and patients might even be encouraged to try gaining weight prior to beginning radiation or chemotherapy. While nutrition is certainly important, high-calorie diets might be recommended to ensure that patients have enough energy during treatment and to combat the muscle loss that might occur when the body is forced to manufacture additional glucose (the primary nutrient for the brain) and is not otherwise getting enough exercise to encourage building more muscle mass.

Weight loss may occur due to treatment side effects

One of the most common side-effects of cancer treatment is nausea. Radiation therapy that is used to treat areas near the digestive tract is very likely to cause issues with nausea, as well as inducing vomiting or diarrhea. These issues may persist for weeks, even after radiation treatment has concluded, if there was damage to the intestinal lining or the treatment caused excessive inflammation. During such time, a patient may have difficulty keeping any food down or might have a drastically reduced appetite.

Finding foods that are easier to digest is one important way to combat nausea, but it may be necessary to also utilize a combination of drugs like Imodium to slow the digestive process down and anti-nausea drugs to reduce the urge to vomit. Too much diarrhea may also lead to dehydration, which patients must be wary of. Generally, however, the effects caused by radiation therapy are quick to clear up after treatment is over. If a patient has lost significant weight during the process, it should be possible to regain this weight through healthy diet and exercise as needed.

Side effects can make eating difficult

Chemotherapy and targeted therapies also have the potential for creating problems with nausea, vomiting, and diarrhea. Because such treatments often take place over a much longer period of time than radiation, consistent monitoring of the patient’s weight is useful.

Aside from digestive issues affecting appetite or the ability to keep food down, other side effects may make eating difficult. Mouth sores, trouble swallowing or chewing, and changes in the way foods taste or smell are just some of the side effects that can make meals difficult. Depression also plays a role, with many patients and caregivers not realizing the importance of maintaining good mental health during treatment.

Weight loss may be triggered directly by cancer tumors

It was long believed that the main reason for cancer patients to lose weight even when they increased their caloric intake was the hungry nature of cancer cells. In effect, tumors would be consuming so much energy that the rest of the body would have to resort to burning fat and muscle mass to feed healthy cells and nourish the brain.

Recent research has shown that there are two types of fat in the human body, referred to as “white fat” and “brown fat,” the latter being a specialized type of fat that actually burns energy to keep the body warm. Brown fat is typically found in infants, but healthy adults mostly have white fat. In some cancer patients, it has been noted that white fat changes to brown fat, contributing to weight loss. This may also possibly spur the onset of cachexia, a condition where the patient loses both fat and muscle mass at a rapid rate.

Tumors may secrete hormones or other chemicals that trigger cachexia or the development of brown fat. Cachexia, also associated with other conditions such as rheumatoid arthritis, is directly responsible for a large percentage of cancer deaths.

Treating weight loss is essential

Palliative care is available to treat most of the symptoms that cause weight loss in patients. Working with a nutrition specialist in conjunction with a medical oncologist may help patients retain and even regain their weight. When eating is particularly difficult, intravenous nutrient therapy may be used. For most patients, however, a combination of adjusted diet and palliative medications will help maintain a healthy weight.

Patients can take action.

Drink fluids

Your body cannot function well if it is not hydrated, and fluids are necessary for flushing toxins.

Eat a high-protein, balanced diet

You not only need to protect lean muscle mass, but you want to be able to build muscle.

Increase your calories

Avoiding empty calories like processed sugars is probably good, but it is important to eat nutrient-rich foods that can provide the extra energy necessary for successful treatment. Smoothies, protein shakes, and plenty of small, frequent snacks can help to raise the calorie count while providing a good nutritional balance.

Stay physically active

Exercise matters for many reasons, ranging from enhanced immune system performance to increased energy. But when it comes to retaining body mass, muscles must be exercised.

Treating cancer requires treating the whole patient. Weight gain or loss may offer clues to the patient’s overall well-being and the success of treatment. As part of patient care (or self-care), paying attention to what we eat and how it affects us plays a vital role in remaining healthy — in or out of active treatment.1-5



  1. Weight Loss. Available at:
  2. Why Do Cancer Patients Waste Away? Research Finds New Clues. Healthline. Available at:
  3. Signs and Symptoms of Cancer. American Cancer Society. Available at:
  4. Coping with Cancer-Related Weight Changes and Muscle Loss. CancerCare. Available at:
  5. Aoyagi, T., Terracina, K. P., Raza, A., Matsubara, H., & Takabe, K. (2015). Cancer cachexia, mechanism and treatment. World Journal of Gastrointestinal Oncology, 7(4), 17–29. Available at: