DENVER - If the nightly dessert after dinner could cause cancer, would you ease up on the sweets?

Millions of Americans have stopped smoking out of concerns over the risk of lung cancer. Now, researchers are finding extra body fat causes just as great of a risk of getting some kind of cancer.

"One cancer in five - or 20 percent - in the United States is due to carrying extra body fat," Dr. Tim Byers, Associate Director for Cancer Prevention and Control at the University of Colorado Cancer Center.

Byers says over the last 20 years, there's been growing evidence that extra body fat increases the risk for common cancers. How that happens varies depending on the specific cancer.

"For some cancers, we don't really know why the extra body fat increases cancer risk," Byers said.

For example, the reason behind the risk for kidney cancer is a mystery that Byers is trying to figure out.

"For liver cancer, it looks like the fat cells infiltrate into the liver and cause local inflammation which drives cancer in the liver," Byers said.

Byers refers to the increased risk of esophageal cancer as a "mechanical problem." Extra body fat increases pressure in the abdomen which causes reflux which damages the esophagus, thereby opening the door for cancer.

"For breast cancer, we know the extra body fat that women carry increases their estrogen levels," Byers said. "That's good for some things and bad for others. One of the things it is bad for is that it increases risk for breast cancer and endometrial cancer."

Byers and his colleagues on the University of Colorado Anschutz Medical Campus studied 700 women who had survived breast cancer. The goal was to determine if intentional weight loss might reverse the risk of a recurrence of the disease.

Half of the women in this study were in put in weight loss groups; the other half were in a group that only received weight loss advice. Byers said that the women in the "weight loss group" dropped, on average, 7 percent body fat. Their estrogen level also dropped to a healthy level, Byers said.

"Our hope now is to extend this study to 2,500 women with breast cancer to determine whether this intentional weight loss, which we know is good for general health, might also reduce the risk of breast cancer recurrence," Byers said. "We think it probably will. We think weight loss should be a standard of practice in oncology care for women after breast cancer."

Byers is optimistic that the message of living a healthier lifestyle is getting through to people.

"What we're seeing around the country, and Colorado as well, is that the steep incline in body fat we've seen over the last 30 years have begun to flatten out," Byers said. "I think we're going to turn this around."

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