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.
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.