Obesity and Cancer Risk

The simple versionExplain▾

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.

Reaching and keeping a healthy weight is one way to lower cancer risk.

How doctors measure body fatExplain▾

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 fatExplain▾

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. For these, people with severe obesity can have several times the risk of people at a healthy weight.

How extra fat may lead to cancerExplain▾

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?Explain▾

This is an active area of research. Some studies suggest that losing weight lowers the risk of certain cancers, such as breast cancer after menopause and uterine cancer. Weight loss from surgery has also been linked to lower risk of some cancers.

The evidence is still growing, and losing weight is not always easy. But a healthy weight brings many other health benefits, too. Even a modest, steady weight loss can be a step toward better health.

Weight and people who already have cancerExplain▾

For people who already have cancer, extra body weight may affect their care. Research suggests it can play a role in quality of life, the chance of a cancer returning, and survival for some 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 weightExplain▾

Reaching a healthy weight is not about quick fixes or strict, short-term diets. Steady habits that you can keep tend to work best. Helpful steps include:

• Building meals around vegetables, fruits, whole grains, and beans.
• Cutting back on sugary drinks and highly processed foods.
• Moving your body regularly, even with simple activity like walking.
• Getting enough sleep, since poor sleep can affect weight.
• Setting small, realistic goals rather than aiming for large, fast changes.

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. Even a modest, steady weight loss can improve your health and lower some cancer risks.

For many people, working with a health professional makes the process easier. A doctor, dietitian, or weight-management program can offer a plan suited to your needs and health history.