Cancer, treatment and unplanned weight loss - why does it happen?

A diagnosis of cancer brings with it many physical and emotional challenges and changes to your life. The cancer itself and cancer treatments like chemotherapy, radiation therapy and surgery can have a negative impact on what you are able to eat and how your body absorbs food. This is why weight loss and under-nutrition are common for people living with cancer, from before diagnosis, during cancer treatment and over time.1-3

does unplanned weight loss impact on my health?

Cancer and cancer treatments may place a high demand on the body. Unplanned weight loss during illness or treatment is mainly muscle loss, whereas fat mass is maintained into advanced stages of cancer. Unfortunately, this weight loss with muscle wasting is never healthy or beneficial, even when initial weight is high.

Weight loss and muscle wasting may lead to treatment interruptions, difficulty coping with treatment side effects, a decreased response to therapy, weakness and a poor quality of life.

In fact, weight loss has been shown to worsen the overall outcome of cancer management compared to people who are able to maintain their weight throughout their cancer course.3-6

  1. Laviano A, Meguid MM. Nutritional issues in cancer management. Nutrition 1996; 12(5): 358-71.
  2. Ravasco P, et al. Nutritional deterioration in cancer: the role of disease and diet. Clinical Oncology. 2003; 15(8): 443-50.
  3. Marshall K, Loeliger J. Investigating Practices Relating to Malnutrition in Victorian Cancer Services

– Phase I, full technical report. Department of Health, State Government of Victoria, Melbourne; 2012.

  1. Fearon K, et al. Definition and classification of cancer cachexia: an international consensus. Lancet Oncol. 2011; 12(5):489-95.
  2. Arends J, et al. ESPEN guidelines on nutrition in cancer patients. Clin Nutr. 2016; doi: 10.1016/j.clnu.2016.07.015.
  3. Martin L, et al. Diagnostic criteria for the classification of cancer associated weight loss. J Clin Oncol. 2015 Jan 1;33(1):90-9.

It’s important that you give your body the nutrients it needs to keep your weight stable, stay strong during surgery, chemotherapy and/or radiation therapy, and to support recovery after these treatments.