Physicians Must Spread Message about Obesity-Cancer Link

Wendy Demark-Wahnefried, Ph.D., R.D.
The American Cancer Society estimates that obesity contributes to as much as 33 percent of all cancer-related mortality in the United States. While there continues to be uncertainty about how specific aspects of excess adiposity, excessive energy intake, and physical inactivity relate to cancer, there is no debate that these contribute to a serious health problem.


Wendy Demark-Wahnefried, PhD, RD, Associate Director for Cancer Prevention and Control for the UAB Comprehensive Cancer Center, says obesity is a risk factor for at least six different cancers. “Those cancers are postmenopausal breast, colorectal, endometrial, kidney, pancreatic and esophageal,” she says. “While there is no consensus yet, evidence is also growing for cancers of the ovary and gallbladder.”


Demark-Wahnefried says researchers have found several clues as to how obesity affects the risk for these cancers. “It could be hormone driven in some cancers like breast cancer,” she says. “Adipose tissue can convert precursor hormones to estrogen, which could fuel breast cancer. If a person has excess fat in the body, she also might have less of a sex hormone binding globulin. As a result, more free sex hormones are present to interact with tissue and can cause mayhem in the body.”


Insulin is another hormone that is present in higher levels in the obese. “People with uncontrolled diabetes are at risk for cancer. The higher insulin levels also can act as a fuel for cancer, but more recent data suggest that people do not even have to have diabetes for this to occur,” Demark-Wahnefried says. “Another growth factor – vascular endothelial growth fact (VEGF) – seems to play a role in obesity. People who have a high VEGF typically have more aggressive cancers.”


Demark-Wahnefried points out that there could be a multitude of pathways leading to these cancers, “or it could be a combination of them all – a magic cocktail of growth factors,” she says. “Nobody had all the answers yet.”


Much of the research at the Comprehensive Cancer Center focuses on nutrition and energy balance to fight the obesity that has given Alabama the distinction of being the nation’s second most obese state. Demark-Wahnefried is working with UAB researchers in the Office of Energetics to find ways to help people use good nutrition and physical activity to balance energy intake with energy expenditure. “We want to strive for energy balance – take in only what we need so we don’t gain weight,” she says. “For those who are overweight, we strive to create negative energy balance to achieve a healthier weight.”


Demark-Wahnefried has done a lot of research on delivering diet and exercise intervention to cancer survivors. Her most recent study, Reach Out to Enhance Wellness (RENEW), tested the impact of a diet-exercise mailed material/telephone counseling program on weight loss in 641 prostate, colorectal and breast cancer survivors. This study was effective not only in improving diet and exercise behaviors, but also in promoting durable weight loss.


In another pilot study, Demark-Wahnefried and her colleagues paired cancer survivors with a master gardener from the Alabama Cooperative Extension. The gardeners taught them to grow their own food. As a result, participants saw improvement in diet, physical activity and their functional status. The study was so successful that Demark-Wahnefried has applied for a grant that would allow researchers to broaden the study. “There is a lot of enthusiasm both here at UAB and at the Cooperative Extension for continuing this study,” she says.


In order for patients to benefit from the research linking cancer to obesity, Demark-Wahnefried says it is imperative that they get the message that they might be at risk. She says physicians are the best messengers to reach the many Alabamians who need to know. “Studies show that physicians have the highest impact on a person’s lifestyle behaviors, so they need to get the message out to their patients who have a weight problem that they are at risk for cancer,” she says.


For cancer prevention and for cancer survivors, the American Cancer Society recommends that people:

  • Achieve and maintain a healthy weight throughout life,
  • Adopt a physically active lifestyle,
  • Consume a healthy diet with an emphasis on plant foods, and
  • Limit consumption of alcoholic beverages.


Cancer is one disease that scares people, Demark-Wahnefried says, and physicians need to take every opportunity to reinforce these recommendations. “Physicians are on the front line in this fight against cancer. They have a responsibility to talk to their at-risk patients,” she says. “I know they don’t have a lot of time to help everyone, but they can refer patients to the appropriate sources for help. More people are surviving cancer, and there are a lot of things we can do to help give them that chance.”



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