ST. LOUIS _ Carrying extra weight is a risk factor for eight more types of cancer, according to a review of more than 1,000 medical studies.
Obesity is now linked to an increased risk of developing cancer of the thyroid, liver, stomach, gall bladder, pancreas and ovaries, plus meningioma, a type of brain tumor, and multiple myeloma, a blood cancer. Earlier research has shown links between obesity and cancer of the breasts, colon, esophagus, kidneys and uterus.
The researchers did not pinpoint a percentage of increased risk caused by obesity, but were able to rule out other risk factors like smoking to make the connections.
"We know for pancreas cancer that smoking is a cause, we know that for liver cancer smoking and alcohol are causes, and now we have this evidence that obesity is clearly a contributing cause as well," said Dr. Graham Colditz of Washington University, who led the research group under the World Health Organization.
More than 40 percent of U.S. women and 35 percent of men are obese, according to the Centers for Disease Control and Prevention. Meanwhile, cancer has surpassed heart disease as the No. 1 cause of death in 22 states, not including Missouri or Illinois.
Colditz said the concern is that cancer deaths will continue to increase because of a lack of successful treatments available for many types of the disease, whereas other killers like heart disease and diabetes are more easily managed.
But the research also points to possible cancer prevention effects from healthy diets and maintaining normal weight. The researchers tried to figure out if losing weight reduces the risk of cancer. They looked at women who had lost weight through surgery and found there were significant reductions in breast and endometrial cancers compared to obese women.
"A lot more work is needed in that area but there is promising evidence that weight loss can reverse some of that adverse effect of weight gain and obesity," Colditz said.
The report was published Wednesday in the New England Journal of Medicine.
