Several cancers are associated with excess body fat; there is no single “obesity-related cancer.” An association describes a pattern seen across groups of people. It cannot tell whether one person will develop cancer, and it is not a reason to blame someone who has a diagnosis.
Which cancers are associated?
The National Cancer Institute lists increased risks for several cancers, including:
- Endometrial cancer (the lining of the womb), ovarian cancer, and breast cancer after menopause.
- Colon and rectal, pancreatic, gallbladder, liver, and kidney cancers.
- Adenocarcinoma of the esophagus, cancer of the upper stomach, thyroid cancer, and multiple myeloma.
These are different diseases with different risk factors. A link at the population level does not mean body weight caused a particular person's cancer. People at many body sizes can develop these cancers, and many people with excess body fat never do.
What does “increased risk” mean?
Risk is about likelihood, not certainty. Body mass index, or BMI, is commonly used in research to group people by weight and height, but it is an indirect measure of body fat. BMI alone cannot describe a person's health or predict whether they will develop cancer. A discussion of personal risk needs more context than one number.
For someone who already has cancer, population risk statistics cannot explain exactly why their cancer developed. It can be more useful to ask which concerns matter for their care now and what support they need, rather than trying to assign a single cause.
Why might there be a link?
Researchers are studying several possible pathways. These include changes in levels of estrogen, insulin and related growth signals, and long-lasting inflammation. Such pathways may help explain some associations, but they do not provide a simple cause for every cancer.
Nutrition during cancer care
Questions about long-term cancer risk are different from nutrition needs during treatment. Appetite, weight, and the ability to eat can change, and a person may need enough calories and protein to support their current care. A registered dietitian can work with the person, family, and care team to understand their needs. A general weight-loss message may not fit an individual's situation.
Questions to discuss
- Which risk factors matter in my own health history?
- What are my nutrition priorities right now?
- Would support from a registered dietitian be helpful?
- Who can help me make sense of conflicting advice about weight and cancer?
Further reading
National Cancer Institute: Obesity and Cancer
National Cancer Institute: Nutrition in Cancer Care