Overweight, Obesity Linked to Cancers
Study Shows High Body Mass Index Ups Risk of Common and Rare Cancers
By
Salynn Boyles
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.
Estimating Future Risk
Being able to quantify cancer risk in relation to body weight should help
public health officials estimate the impact of both the aging of the population
and the obesity epidemic on cancer rates over the next decade and beyond,
Renehan says.
Nutritional epidemiologist Susanna Larsson, PhD, of Stockholm's Karolinska
Institutet tells WebMD that the analysis makes it clear that more needs to be
done at the community level to help people maintain healthy body weights.
"We have not seen the initiatives that will be needed to address this
problem," she says.
American Cancer Society epidemiologist Michael Thun, MD, MS, agrees.
"If people could lose weight easily they
would," he tells WebMD. "But the fact is, there are many, many things
in our social and physical environment that make it easy to gain weight. Food is
everywhere, and physical activity is no longer
built into our daily lives. For most people it is voluntary."
Although awareness is growing, Thun says most people still don't know that
being overweight or obese makes them more likely to get cancer.
"They know that obesity is linked to heart disease and diabetes," he says. "But
the average person on the street would still be surprised that obesity is
related to cancer risk."
SOURCES: Renehan, A.G. The Lancet, Feb. 16, 2008; vol 371: pp 569-578. Andrew G. Renehan, PhD, department of surgery, School of Cancer Studies,
University of Manchester, England. Susanna C. Larsson, PhD, division of nutritional epidemiology, National
Institute of Environmental Medicine, Karolinska Institutet, Stockholm,
Sweden. Michael J. Thun, MD, MS, vice president of epidemiology and surveillance
research, American Cancer Society, Atlanta. National Cancer Institute web site. American Cancer Society web site.
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