Obesity & Cancer Risk: What’s the Connection?

December 5, 2017 | by City of Hope

Some risk factors for cancer are out of your control. You can’t change your genetic history, for example. But many factors that increase the risk of developing cancer are within your control.

Along with quitting smoking, maintaining a healthy weight is one of the best ways to lower the odds of developing cancer, said Elaine Siu, M.S., R.D., C.N.S.C., a clinical dietician at City of Hope.

Researchers are still exploring the specific ways that being overweight could lead to cancer. But it’s clear there’s a connection. Here’s what we know so far.

The body fat-cancer connection

An estimated 70 percent of U.S. adults are overweight (with a body mass index, or BMI, of 25-29.9) or obese (with a BMI greater than 30). (You can calculate your BMI here.)

Higher amounts of body fat are linked to an increased risk of many types of cancer, including:

  • Breast cancer
  • Colorectal cancer
  • Endometrial cancer
  • Esophageal adenocarcinoma
  • Gallbladder cancer
  • Gastric cardia cancer
  • Kidney cancer
  • Liver cancer
  • Meningioma
  • Multiple myeloma
  • Ovarian cancer
  • Pancreatic cancer
  • Thyroid cancer

Being either overweight or obesity can boost cancer risk, “though studies often show that the higher the BMI, the greater the risk,” Siu said.

Cancer biology

There are several ways that excess bodyweight might contribute to cancer:

  • Inflammation. “People who are overweight or obese tend to have chronic low-level inflammation,” Siu said. Over time that inflammation can damage DNA, which can lead to the development of cancer.
  • Hormones. Fat cells produce excess amounts of the hormone estrogen. High estrogen levels have been linked to breast, ovarian and endometrial cancers. Fat tissue also releases a group of hormones called adipokines, which can stimulate or prevent cells from growing.
  • Insulin. People who are obese are more likely to have high levels of insulin in their blood, which may contribute to colon, kidney, prostate and endometrial cancers.

Lowering your risk

The good news is that by lowering your BMI, you can lower your risk, Siu said. “Even a slight decrease in weight seems to be beneficial.”  

To reach a healthier weight, she recommends taking it slow. “You don’t have to make drastic lifestyle changes,” she said.

Siu recommends avoiding sodas and fruit juices, which pack a lot of calories but offer little in the way of nutrition. Focus on eating a mostly plant-based diet rich in fiber and a variety of fruits and vegetables of every color. And try to increase physical activity.

The key is to start with small, achievable goals and build on them. “Take it one step at a time,” she said.

Reaching a healthier weight has a multitude of benefits – and cutting cancer risk is high on the list.

For Wellness lifestyle tips and healthy recipes visit Living Well. Living well is a collection recipes, articles and videos created to support the emotional, mental, physical and spiritual well-being of cancer patients and their families. Brought to you by City of Hope Cancer Center.

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