physical activity—or rather, the lack of it.

“In terms of physical activity, that impact

is strongest in gastrointestinal cancers,

particularly colorectal cancer,” Dr. Demark-

Wahnefried says. “It’s extremely important

in prevention, because if you’re active and

eat a healthy diet, your digestive system is

more active and efficient.” In fact, some

studies have shown that physical activity

can reduce the risk of colorectal cancer by as

much as 50 percent.

OBEsIty IN REsEARCh

Obesity is a major research focus at the

Cancer Center, where it is being studied for

its connection to various cancers from ani-

mal models in the laboratory to population-

based studies among survivors.

Cancer Center scientist Tim Nagy,

Ph.D., is vice chair for research in the

Department of Nutrition Sciences. His

research focuses on the role of caloric

restriction and body fat and its impact on

cancer—particularly why obese individuals

are more likely to die from the disease than

non-obese people.

“Our research suggests that elevated

risk is actually caused by addition of body

fat. Scientists no longer think of body fat as

tissue that just holds excess calories, hold-

ing energy in reserve,” Dr. Nagy says. “In

fact, extra body fat is an endocrine tissue

that produces hormones. As you increase

the amount of fat, certain hormones are

produced in excess, and other hormones are

produced less. We think that many of these

hormones may play a role in the discrepancy

in mortality rates.”

Dr. Nagy and his team have also found

that among overweight women who reduced

their weight to normal levels, cancer cells

tend to grow more slowly. Cell death occurs

less in the overweight state compared to a

more normal weight, meaning the cell cycle

is better regulated in leaner individuals.

These findings could have an impact on the

relationship between obesity and metastasis,

which is significant because “people mostly

die from metastatic disease rather than ini-

tial tumors,” Dr. Nagy says. He adds that

obesity may provide tumors with an envi-

ronment in which they can grow and flour-

ish, while leanness starves them.

While Dr. Nagy studies the obesity-

cancer connection at the cellular level, Dr.

Demark-Wahnefried, who has been involved

with some of the largest obesity studies

in the nation during her tenures at Duke

University and M.D. Anderson Cancer

Center (see Center Profile, page 14), works

at the population level.

One of Dr. Demark-Wahnefried’s major

projects currently is the ENERGY (Exercise

and Nutrition to Enhance Recovery and

Good Health for You) study in collabora-

tion with the University of California-San

Diego, the University of Colorado in Denver

and Washington University in St. Louis.

ENERGY is recruiting 800 breast cancer

survivors from across the United States (200

of whom will be from the Birmingham area)

who are overweight or obese and up to five

years post-diagnosis. During the study, the

women are assigned to either intensive inter-

ventions with classes or sessions with profes-

sional dieticians.

“The question we’re trying to answer

is this: Is it feasible to promote weight loss

4 u A b C o m P r e H e N S I V e C A N C e r C e N T e r

Dr. Wendy Demark-Wahnefried with some of the master gardeners from the Cancer Center’s gardening

project: (left to right) lathia banks, Dr. Wendy Demark-Wahnefried, Hope long, Jeanne bearden, leAnne

Porter, leonora roberson and Harold Deason