Weight loss

Losing weight when you are not trying to is a common symptom in people with cancer.

Weight loss and cancer

Weight loss is common in people with cancer. It might be one of the reasons why you first go to the doctor.

There are several causes of weight loss and your doctor can treat many of these.

Losing weight is often associated with a loss of appetite. But this is not the only cause. For people with cancer, other causes are:

  • pain

  • a swollen tummy (abdomen)

  • feeling and being sick (nausea and vomiting)

  • difficulty swallowing

  • feeling full because of a swollen (enlarged) liver

  • a blocked bowel

  • high levels of calcium in the blood

  • not being able to absorb nutrients from food (malabsorption)

Cachexia

Some people may lose weight despite eating normally. This is called cachexia (pronounced kak-ex-ee-a). With cachexia, your body may not be absorbing all the fat, protein and carbohydrate from the food you eat. And you may be burning calories faster than normal.

People with cachexia lose muscle and often fat too. Scientists think that cancer releases chemicals into the blood. The chemicals contribute to the loss of fat and muscle.

Continuous weight loss can be worrying and a constant reminder of your illness. It can affect your quality of life and how you feel about yourself.

Weight loss can depend on cancer type

Weight loss is more common in some cancer types.

About 60 out of 100 people with lung cancer (60%) have a loss of appetite and significant weight loss at the time of their diagnosis. In people with upper gastrointestinal cancer, this number is 80 out of 100 people (80%). Upper gastrointestinal cancers include:

  • food pipe (oesophagus) cancer

  • stomach cancer

  • small bowel cancer

  • pancreatic cancer

  • liver cancer (including primary and secondary liver cancers, bile duct and gallbladder cancer)

Monitoring your weight

Your doctor will want to find out the cause if you are losing weight without dieting.

You can:

  • weigh yourself once a week at the same time, wearing the same clothes
  • keep an eye on how tight or loose your clothes, watch or rings are if you don't have scales

Let your healthcare team know if you are worried about changes in your weight.

  • ESMO Handbook of Nutrition and Cancer (2nd edition) 
    A Jatoi, S Kaasa and M Strijbos
    ESMO Press, 2023

  • Nutrition in cancer patients
    P Ravasco
    Journal of Clinical Medicine, 2019. Volume 8, 1211

  • Cancer cachexia in adult patients: ESMO clinical practice guidelines
    J Arends and others
    Annals of Oncology, 2021. Volume 6, 100092

  • Diagnostic criteria for the classification of cancer-associated weight loss
    L Martin and others
    Journal of Clinical Oncology, 2015. Volume 33. Pages 90-99

  • ESPEN expert group recommendations for action against cancer-related malnutrition
    J Arends and others
    Clinical Nutrition, 2017. Volume 36. Pages 1187-1196

  • The information on this page is based on literature searches and specialist checking. We used many references and there are too many to list here. If you need additional references for this information please contact patientinformation@cancer.org.uk with details of the particular issue you are interested in.

Last reviewed: 
13 Sep 2023
Next review due: 
14 Sep 2026

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