RESEARCHERS ESTIMATE THAT OBESITY causes about 20% of instances of cancer. Over the past several decades, hundreds of studies have linked obesity and cancer risk, and excess weight has been associated with higher rates of cancer recurrence and mortality.

However, while 94% of Americans recognize that tobacco use poses a cancer risk and 84% know that excessive exposure to the sun can cause cancer, only 50% are aware that weight affects cancer risk, according to results of the American Institute for Cancer Research 2017 Cancer Risk Awareness Survey.

The specifics of how weight increases cancer risk are still not fully understood. Many studies define obesity using body mass index (BMI), a measurement computed from a person’s height and weight. The BMI is easy to measure, but it neglects important details like a person’s muscle mass or fat distribution, as well as lifestyle factors associated with weight, like diet and exercise.

Some physicians are focusing on how to help cancer patients lower their mortality and recurrence risks via those lifestyle factors. “After diagnosis with a serious medical condition, people might be more receptive to making lifestyle changes,” says Jennifer Ligibel, a breast oncologist at Dana-Farber Cancer Institute in Boston. “Cancer diagnoses can be teachable moments.”

Ligibel is the lead investigator of the Breast Cancer Weight Loss study, a lifestyle intervention program for women diagnosed with breast cancer who are overweight or obese. Since 2016, more than 1,900 women have volunteered to be randomly assigned to either a two-year weight-loss program or to general health education alone. Women in the weight-loss program receive coaching over the phone on diet and exercise as well as general health education in the form of written materials and online webinars, while women in the other study arm receive only the general health education.

Other studies focus specifically on diet and exercise rather than weight loss. The Lifestyle Intervention for oVarian cancer Enhanced Survival (LIVES) study coaches women with previously treated stage II, III or IV ovarian, fallopian tube or primary peritoneal cancer on how to meet the study’s diet and exercise goals while dealing with symptoms resulting from treatment, like fatigue. “We’re not focused on weight loss; we’re focused on diet quality and moving your body more,” says LIVES study co-investigator Tracy Crane, a registered dietitian nutritionist at the University of Arizona in Tucson. She adds that people in the study with weight to lose who change their dietary and exercise habits may see their weight drop.​​​

Lasting Change

Registered dietitian nutritionist Tracy Crane of the University of Arizona in Tucson offers these tips on how to make lifestyle changes that stick.​

  • Start small. “Don’t take on the whole world in one day,” says Crane. “Have small goals, like adding one vegetable serving a day or parking a couple spaces farther away at the grocery store.”
  • Give yourself time. If you’ve undergone treatment recently, keep in mind that it may take time for certain aftereffects, like symptoms of neuropathy, to fade and for your energy level to improve.
  • Rest up. Getting enough sleep​ is crucial to staying motivated to achieve your diet and fitness goals. “It’s hard to make healthy food choices when you’re tired,” says Crane.

In addition to analyzing blood samples and measuring the effects of these changes on disease progression, researchers are also assessing how coaching promotes lasting change. “After diagnosis and treatment, this is how you can take some control over your health,” says Crane. “My greatest success is when people tell me ‘This has become my new lifestyle.’”​