July 17, 2002 -- Need another reason to lose those extra pounds
July 17, 2002 -- Need another reason to lose those extra pounds? How about reducing your risk of getting cancer?
Though obesity and cancer are major concerns for many Americans, most people are unaware that being overweight increases their risk for cancer, according to an American Institute for Cancer Research study. Of the more than 1,200 adults they polled this June, only 25% knew there as a link between the two.
Research now shows that fat doesn't just sit there -- it actively alters the body's normal hormonal and chemical balances, sending signals that, under the right conditions, cause cancer to grow.
"The more we understand about obesity, the more we realize that simply being overweight and inactive -- in other words, living the modern American lifestyle -- produces basic hormonal and metabolic changes," says George Bray, MD, of the Pennington Biomedical Research Center in Louisiana, in a news release.
"These changes make it easier for cancer to gain a foothold," Bray says.
Bray presented his research at the World Cancer Research International, a scientific conference on diet and cancer. New technologies are allowing scientists to study the influence of obesity on the body more precisely than ever before, he says.
"Most of us look at our guts and our hips and our love handles and think of fat as an inert substance that merely collects and hangs off of us," says Bray.
However, research shows that body fat produces an excess of substances such as sex hormones and insulin. Under normal circumstances these are perfectly normal substances that contribute to natural body chemistry. But in an obese person, higher levels of these chemicals can urge cells to grow and divide at an accelerated rate.
Some scientists predict that excess body fat will ultimately prove to be strongly implicated in the development of the so-called "hormonal" cancers -- those of the breast, prostate, ovary, uterus, and testicle, says Bray.
But obesity doesn't seem to affect only these types of cancers.
In fact, one study of almost 90,000 women -- between 40 and 59 -- shows that obesity doubles the risk of colorectal cancer in women. Researcher Thomas E. Rohan, MD, PhD, chairman of epidemiology and social medicine at Albert Einstein College of Medicine in New York, published the results in the August issue of the medical journal Gut.
Before menopause, fat tissue is only a minor source of total estrogen circulating in the body. Therefore, being very overweight in youth and young adulthood may increase a woman's risk for bowel cancer, they say.
However, being very overweight after menopause did not increase the women's risk of bowel cancer, reports Rohan. If anything, their risk slightly decreased. He suggests that after menopause, fat tissue is an important source of estrogen, which may be protective and counteract the harmful effects of insulin in the bloodstream.
Bottom line: "Avoiding weight gain is one of the most important things we can do to prevent cancer," says Bray.
