The short answer
Having overweight or obesity raises the risk of at least 13 types of cancer. Extra body fat can change hormones, insulin levels, and inflammation in ways that may help cancer grow. Studies of weight loss show mixed results, so ask your care team what is right for you.
Overweight and obesity are linked to at least 13 types of cancer.
NCI says the risk increases are largest for cancers of the uterus (endometrium) and esophagus in people with severe obesity.
Extra body fat can raise hormone and insulin levels and cause inflammation, which may help cancer grow.
Studies found lower breast and endometrial cancer risk in people who lost weight intentionally, but randomized trials of weight-loss diets were inconclusive.
Watch: Body weight and cancer risk
45 sec · Captioned · Overweight and obesity are linked to at least 13 types of cancer.
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This page explains how body weight is linked to cancer risk. It covers which cancers are involved, why the link may exist, and steps toward a healthy weight.
The simple version
Carrying too much body fat raises the risk of cancer. Research links overweight and obesity to at least 13 different types of cancer.
Obesity is a condition where a person has an unhealthy amount or spread of body fat. It is common, and it can affect health in many ways beyond cancer, such as heart disease and diabetes.
Talk with your care team about what a healthy weight means for you.
How doctors measure body fat
Doctors often use a number called body mass index, or BMI. BMI is based on your height and weight. It gives a rough idea of how much body fat a person has.
BMI is useful, but it is not perfect. It cannot tell exactly how much fat a single person has. So doctors sometimes also look at:
- Waist size
- The ratio of waist to hips
- Other body measurements
Where fat sits matters, too. Fat around the belly and organs, called visceral fat, seems to carry more health risk than fat just under the skin.
Which cancers are linked to body fat
Studies that followed large groups of people over time show that higher body fat is linked to these cancers:
- Uterus (endometrial cancer)
- Esophagus
- Upper stomach
- Liver
- Kidney
- Pancreas
- Colon and rectum
- Gallbladder
- Breast (after menopause)
- Ovary
- Thyroid
- Multiple myeloma (a blood cancer)
- Meningioma (a type of brain tumor)
The links are strongest for uterine and esophageal cancers. NCI says people with severe obesity have about seven times the risk of endometrial cancer and nearly five times the risk of esophageal cancer, compared with people at a healthy weight.
How extra fat may lead to cancer
Researchers have found several ways that extra body fat may raise cancer risk:
- Hormones. Fat tissue makes extra estrogen, which is linked to breast, uterine, and other cancers.
- Insulin. People with obesity often have high insulin levels, which are tied to several cancers.
- Inflammation. Extra fat can cause ongoing, low-level inflammation, which may help tumors grow.
- Growth signals. Fat cells release chemicals that can affect how other cells grow.
Does losing weight help?
This is an active area of research. NCI says studies found lower risks of breast and endometrial cancers among people who lost weight intentionally. Randomized controlled trials of weight-loss diets have been inconclusive. Weight loss through bariatric surgery has been associated with reduced cancer risks.
Losing weight is not always easy, and any weight-loss plan is best made with your care team.
Weight and people who already have cancer
For people who already have cancer, extra body weight may affect their care. NCI says obesity may worsen quality of life, cancer recurrence, cancer progression, survival, and the risk of certain second primary cancers.
If you have cancer, your care team is the best guide on whether weight changes would help you. They may suggest working with a dietitian or an exercise program suited to your situation.
Steps toward a healthy weight
Weight is affected by many things, some of them beyond personal control, such as genes, medicines, and life circumstances. So it helps to be kind to yourself. A doctor, dietitian, or weight-management program can offer a plan suited to your needs and health history. Do not start a new diet or exercise program during cancer treatment without asking your care team.
Common questions
How is obesity linked to cancer?
Research shows that people with more body fat have a higher risk of at least 13 types of cancer. Extra fat can raise levels of hormones like estrogen and insulin and cause ongoing inflammation, all of which can help cancer cells grow.
Which cancers are tied to excess body weight?
They include cancers of the uterus (endometrium), esophagus, upper stomach, liver, kidney, pancreas, colon and rectum, gallbladder, breast (after menopause), ovary, thyroid, and two others called multiple myeloma and meningioma. NCI says the risk increase is largest for uterine and esophageal cancers.
What is BMI?
BMI, or body mass index, is a number based on your height and weight. Doctors use it as a rough guide to body fat. It is helpful but not perfect, so doctors may also look at things like waist size.
Does losing weight lower cancer risk?
NCI says studies found lower risks of breast and endometrial cancers among people who lost weight intentionally, but randomized controlled trials of weight-loss diets were inconclusive. Weight loss through bariatric surgery has been associated with reduced cancer risks. Ask your care team what is right for you.
Does obesity affect people who already have cancer?
It can. Research suggests obesity may affect quality of life, the chance of cancer coming back, and survival for some cancers. Your care team can talk with you about what is right for you.
Where does the extra fat matter most?
Fat around the belly and internal organs, called visceral fat, seems to carry more health risk than fat just under the skin. This is one reason doctors sometimes measure waist size.
Questions to ask your doctor
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Last updated: 2026-10-16Next planned review: 2027-07-04
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Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes, and this is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and then compared with the sources listed on it, looking for statements those sources do not back up. That check is not a sentence-by-sentence record and can miss errors. It is not a medical review, and it does not confirm the page is complete or right for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
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