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Overweight, Obesity Linked to Cancers

Study Shows High Body Mass Index Ups Risk of Common and Rare Cancers
By
WebMD Health News
Reviewed by Louise Chang, MD

Feb. 14, 2008 -- If you're overweight or obese you have an increased risk for developing many common and not-so-common cancers, a research analysis shows.

Researchers combined data from more than 200 sets of data -- including more than 282,000 people -- that considered the impact of weight on 15 cancer sites.

Increased weight was most strongly linked to an increased risk for cancer of the esophagus in men and women and for endometrial and gallbladder cancers in women.

A modest association was found between excess weight and the risk for more common malignancies such as postmenopausal breast cancer in women, colon cancer in men, and blood cancer in both sexes.

But carrying extra weight was not associated with an increase in risk for prostate cancer in men, premenopausal breast cancer and ovarian cancer in women, and lung cancer in men and women.

The analysis appears in the Feb. 16 issue of The Lancet.

"We were surprised to find associations to both common and less common cancers," researcher Andrew G. Renehan, PhD, tells WebMD. "We also saw very clear differences between [obesity-related] risk at different sites between the sexes."

BMI and Cancer Risk

Renehan and colleagues from the University of Manchester in England used body mass index (BMI) measures from the studies to assess risk.

BMI is a numerical measure of fatness based on a person's weight relative to height. A BMI of 18.5 to below 25 is considered normal weight, while 25 to just under 30 is considered overweight, but not obese. Someone is considered obese if they have a BMI of 30 or above.

To put the numbers in perspective, someone who is 5-feet 7-inches tall would have a BMI of 25, 30, or 35, respectively, if they weighed 160, 190, or 225 pounds.

In men and women, each 5-point increase in BMI was associated with a roughly 50% increase in relative risk for esophageal adenocarcinoma, which is still relatively uncommon but growing in the U.S.

Other highlights from the analysis include:

  • Among women, each 5-point increase in BMI was associated with a roughly 60% increase in risk for endometrial (uterine) cancer. About 39,000 new cases of the cancer were estimated in the U.S. last year, with 7,400 estimated deaths from the disease. 
  • The link between overweight and obesity and colon cancer was stronger in men than in women; each 5-point increase in BMI was associated with a 24% increase in relative risk among men and a 9% increase in women. 
  • Excess weight was a much stronger risk factor for gallbladder cancer in women than in men, with each 5-point increase in BMI associated with a 59% increase in the relative risk for the cancer in women and no statistically significant increase in men. Gallbladder cancer is rare, with only about an estimated 9,000 new cases diagnosed last year in the U.S. 
  • Each 5-point increase in BMI was associated with a 12% increase in the risk of breast cancer after menopause in women, but no increase in risk prior to menopause. 
  • Increased BMI was also associated with a modest increased risk for blood cancers like leukemia, multiple myeloma, and non-Hodgkin's lymphoma in both men and women.

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