Excess weight in youth linked to increased colorectal cancer in women

Women who were obese as teens at increased risk of colorectal cancer

Women who were overweight or obese early in life are at an increased risk of developing colorectal cancer as adults, according to a new study.

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Researchers analyzed data from over 75,000 American women and 34,000 American men. During 22 years of follow-up, they identified 1,292 cases of colorectal cancer -- a term used for cancer that begins in the colon or rectum -- in women and 808 cases in men.

They found that, compared to women who were lean in childhood, women who were overweight as children had a 28 percent higher risk of developing colorectal cancer. Women who were overweight as teenagers had a 27 percent higher risk of colorectal cancer than women who were lean as teens.

The link between being overweight as a child or teenager and a higher risk of colorectal cancer was not found in men.

"We really don't know why we only observed the association in women and not in men, but since this is still a relatively new area of research, it's too early to conclude that this association does not exist in men," said study senior author Esther Wei, of the California Pacific Medical Center.

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"Our study supports the growing evidence that early life body size can influence risk of colorectal cancer many decades later," she added.

The study was not designed to prove that being overweight as a child or teenager causes colorectal cancer later in life. The findings were published in the journal Cancer Epidemiology, Biomarkers and Prevention.

Colorectal cancer is the third most common cancer diagnosed in men and women in the United States. The lifetime risk is about 1 in 20, with a slightly lower risk in women than men.

According to the Centers for Disease Control and Prevention, about one-third of American children and teens are overweight or obese. In the past 30 years, obesity in children has more than doubled and more than quadrupled in adolescents.

A recent study found that obese women are 41 percent more likely to develop certain cancers than women who are of a normal weight. According to the National Cancer Institute, one possibility explaining the association between obesity and cancer is the fact that fat tissue produces excess amounts of estrogen, high levels of which have been linked to an increased risk of breast and endometrial cancer. Another possibility is that fat cells produce adipokines, hormones that may stimulate or inhibit cell growth.

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