Last Updated: 2003-04-23 17:00:08 -0400 (Reuters Health)
By Alison McCook
NEW YORK (Reuters Health) - A significant proportion of deaths from cancer may be due to excess body weight and obesity, according to an American Cancer Society report.
Based on a study involving almost one million adults, the researchers conclude that 14 percent of deaths from cancer in men and 20 percent of cancer deaths in women may be due to being overweight and obese.
The study's authors estimate that more than 90,000 cancer deaths each year could be avoided if every American maintained a healthy weight.
"Obesity is related to most cancer sites, not just a select few," study author Dr. Eugenia E. Calle told Reuters Health.
Calle said she hopes these results help people understand the devastating impact being overweight or obese can have on health.
"I'm hoping that this study will increase the public awareness that this is yet another important health outcome that obesity puts you at higher risk for," Calle noted.
During the 16-year study, Calle and her colleagues followed more than 900,000 U.S. adults who were free of cancer in 1982, noting if any died of the disease. The researchers measured body weight using body mass index, which takes into account weight and height.
Compared to people of normal weight, those who were overweight and obese had a higher risk of death from a host of different cancers, according to a report in The New England Journal of Medicine.
Among both sexes, excess body weight upped the risk of death from cancer of the esophagus, colon and rectum, liver, gallbladder, pancreas and kidney, as well as for non-Hodgkin's lymphoma and multiple myeloma.
In men, the heaviest individuals were more likely to die from cancer of the stomach and prostate. In women, excess deaths were seen for cancer of the breast, uterus, cervix and ovary.
And the higher the BMI, the more likely a person was to die from cancer, the researchers report.
A BMI of between 18.5 and 24.9 is considered normal, between 25.0 and 29.9 overweight, and 30.0 or more obese.
Among the heaviest people -- with BMIs of at least 40 -- the risk of death from cancer of any type was 52 percent higher in men and 62 percent higher in women than in people with normal BMIs.
"The more weight you have, the higher the risk," Calle said in an interview.
However, the fact that death risk appears to increase incrementally with body weight is somewhat encouraging, she added.
"Losing any kind of weight would help," Calle noted.
She explained that the current study measures risk of death from cancer, but not the risk of developing the disease. Previous research in breast cancer has shown that carrying extra weight can increase the risk of both getting and dying from the disease, Calle said, but for other types of cancer, that may not be the case.
Although the exact reasons why obesity might increase cancer death risk are unclear, Calle said that people with relatively high BMIs also tend to have higher levels of hormones in their bodies, which can predispose them to cancer.
In addition, research suggests that carrying excess weight in the abdomen can disrupt the metabolism of insulin, resulting in a condition that can increase cancer risks, she explained.
People who are obese are also more likely to develop gallstones and reflux disease, which can lead to chronic inflammation in the body and, subsequently, certain types of cancer, Calle added.
In a related editorial, Drs. Hans-Olov Adami of the Karolinska Institute in Sweden and Dimitrios Trichopoulos of Harvard University in Boston write that this is not the first study to suggest that excess body weight increases cancer risk.
However, they write that programs aimed at preventing cancer through weight control have been stymied by a number of reasons, including the fact that other factors such as smoking play a larger role, and researchers remain uncertain why being overweight influences cancer risk.
It remains to be seen whether the latest findings "will provide the necessary additional motivation for controlling body weight in the United States and around the world," Adami and Trichopoulos write.
Trichopoulos has received fees from NutraSweet and Coca-Cola.
SOURCE: The New England Journal of Medicine 2003;348:1625-1638.