Body Weight and Cancer Risk

Aprobado por la Junta Editorial de Cancer.Net, 01/2021

Being overweight or obese (very overweight) means your body has more fat compared to other tissue, such as muscle and bone. Too much extra weight raises your risk of certain types of cancer, as well as your risk for cancer coming back after treatment.

Talking about your weight with your doctor is important, but that can be hard for some people. Some people feel ashamed about their weight. Some people have even experienced discrimination because of their weight. It can also feel overwhelming to change your behaviors, like what and how much you eat and how much you exercise. But even small, simple changes can have a big impact on your health.

It is important to understand what doctors and researchers mean by cancer risk. Not everyone who has risk factors like being overweight or obese will develop cancer. Knowing your cancer risk can help you make healthier choices and can help you know what signs and symptoms to look out for.

Learn more about understanding cancer risk.

Why is being overweight linked to cancer risk?

Researchers are still studying the connection between body weight and cancer risk. They have found several reasons why weight can affect your cancer risk. These include:

  • Extra weight raises your levels of the hormones insulin and insulin growth factor-1 (IGF-1). Too much of this hormone can help some cancers develop.

  • Fat tissue also produces more of the hormone estrogen. Estrogen can help some cancers, like breast cancer, develop.

  • Chronic, low-level inflammation is more common in people who are obese (particularly if they have more belly fat) and that is linked with an increased cancer risk.

  • Fat cells affect the way your body regulates cancer cell growth.

Changes in your weight over your lifetime can also affect your risk of cancer. Studies show that the following factors can affect your risk:

  • Weighing more than most babies at birth

  • Gaining weight as an adult

  • Losing weight and gaining it back over and over

Eating a balanced diet, maintaining your weight, and adding regular exercise to your routine lowers your cancer risk. If you are a cancer survivor, making these healthy choices can also lower your risk of cancer coming back (recurrence).

What types of cancer are linked to being overweight or obese?

The following types of cancer have been linked to being overweight or obese:

  • Breast cancer

  • Uterine cancer

  • Prostate cancer

  • Pancreatic cancer

  • Gallbladder cancer

  • Thyroid cancer

  • Colorectal cancer

  • Head and neck cancer

  • Esophageal cancer

How to determine if you are overweight or obese

A measurement called your "body mass index" or BMI shows if you are overweight or obese. It is based on how much you weigh and your height. BMI measurements and classification can vary, depending on your race and body makeup. BMI is often used in research to help understand how weight is related to cancer, but it does not predict your future health. Talk with your health care team about what your BMI means for your cancer risk.

A healthy BMI is usually between 18.5 and 24.9. A BMI between 25 and 29.5 is considered overweight. A BMI of 30 or higher is considered obese.

Another measurement you can take is your waist measurement. Research shows that people with a larger waist measurement have a higher risk of some diseases, including heart disease and cancer. A healthy waist measurement is under 40 inches (101.6 cm) for men and under 35 inches (88.9 cm) for women.

Maintaining your weight

If you and your health care team are happy with your weight and you do not want to lose or gain weight, you should take steps to maintain your weight. Here are some tips:

  • Eat mostly vegetables, fruits, lean proteins, and whole grains.

  • Eat foods that make you feel full, including healthy fats such as nuts, fish, and olive oil.

  • Avoid highly processed foods like chips, white breads, cookies, and packaged foods with many artificial ingredients.

  • Avoid sugary drinks, such as fruit juice, soda, and other drinks with a lot of sugar. Check the sugar and calories in the your coffee and any alcoholic drinks.

  • Set a goal to do 30 to 60 minutes of physical activity on most days of the week. Physical activity can be moderate or intense. Take a brisk walk, join an exercise class, or go for a run. If you cannot get 30 to 60 minutes, do what you can. Even a few extra minutes a day lowers your cancer risk.

Ask your health care provider to help you figure out how many calories to eat each day. Stick to your daily limit, or as close to it as you can. Also, if you have been diagnosed with cancer, talk with your cancer care team beforehand about any concerns you may have about changes to your eating or exercise plans because of your diagnosis or treatment.

Reducing cancer risk if you are overweight or obese

Eating well and being more active are the best ways to improve your health if you are overweight or obese. Losing as little as 5% to 10% of your total body weight can reduce your risk of developing cancer. It may seem like a small amount, but research shows that it can improve your health. Even if you find losing weight hard, eating a more balanced diet and exercising regularly helps lower your cancer risk.

Here are some things you can do to help you make healthier choices:

Make small changes in your food choices and exercise routine. If you struggle with being more active and eating less, members of your health care team can help. A registered dietitian, exercise specialist, psychologist, or doctor who specializes in weight loss are professionals who can help you make changes.

Get support. It is important to feel supported when trying to make lifestyle changes. Most weight loss programs include sessions with a dietitian or weight loss specialist. They can help you make healthier changes and stick with them over time. Talk to your family about the changes you want to make and ask them to help. It is much easier to make changes if the people you live with make them, too.

Medication. Some health care providers may recommend taking medication if diet and exercise do not work and your obesity is causing other serious health conditions.

Weight loss surgery. If you have a serious health condition related to obesity, such as heart disease or diabetes, weight loss surgery may be an option. Weight loss surgery, also called bariatric surgery, is surgery to make your stomach smaller. There are different kinds of weight loss surgery. This is usually only considered for people who have a BMI of 40 or more or 35 or more with a serious health condition.

It is important to work with your health care team to help you make healthy changes and lose weight. Losing a lot of weight and maintaining a healthy weight can be difficult. A cycle of losing and gaining weight, sometimes called yo-yo dieting, has been linked to an increased risk for cancer. Crash diets, or diets where you do not get all of the nutrition you need, can be dangerous. And, if you have had an eating disorder in the past, you should always speak to your health care provider about changing your eating or exercise habit before you begin.

Questions to ask your health care team

For people seeking to lower their general cancer risk:

  • Does my body weight put me at a higher risk of developing cancer?

  • Will losing weight improve my overall health? Will it lower my cancer risk?

  • How much weight should I lose?

  • What programs and treatments are available to help me make changes to how I eat and exercise?

  • Can you recommend someone to help me with a weight loss program?

  • Where can I find information on healthy eating?

  • Where can I find information on exercise?

For cancer survivors:

  • What are the benefits to my health to making lifestyle changes?

  • Would losing weight affect my risk of cancer recurrence?

  • Are there certain exercises I should avoid due to the disease or its treatment?

  • Is there an oncology dietitian and/or other specialists that I can talk with about making food choices and my exercise routine?

Related Resources

Physical Activity and Cancer Risk

Changes People Can Make to Lower Their Cancer Risk

Food and Cancer Prevention

Survivorship: Healthy Living After Cancer

More Information

Academy of Nutrition and Dietetics: Your Health and Your Weight

National Cancer Institute: Obesity and Cancer Risk

Society of Gynecologic Oncology: A Patient’s Guide to Losing Weight to Reduce Your Risk of Endometrial Cancer