Does Obesity Cause Cancer

By Nancy Menefee Jackson

In addition to the body count from heart disease and other cardiovascular ailments, the trend toward obesity claims 90,000 American lives each year due to cancer.

A massive study, published in the New England Journal of Medicine, links being overweight with an increased risk of cancer.

“For most cancer sites and all the types of cancer, there’s very much a dose response,” says lead researcher Eugenia Calle, Ph.D., director of analytic epidemiology for the American Cancer Society. “There is an increasing risk. The more overweight you are, the more likely you are to die of cancer.”

Researchers followed 900,000 people for 16 years, all of whom were cancer-free when the study began. The heaviest members were found to have death rates that were 52 percent higher for men and 62 percent higher for women than those of people of normal weight. That means that overweight and obesity may account for 14 percent of all cancer deaths in the United States for men and 20 percent for women.

The study confirmed earlier studies that indicated that excess weight was linked to cancers of the breast (postmenopausal), uterus, colon, rectum, kidney, esophagus and gall bladder. The new study also showed that pancreas and liver cancer, non-Hodgkin’s lymphoma, multiple myeloma, and cancers of the stomach and prostate in men and cancers of the cervix and ovary in women are associated with the extra pounds.

That, says Calle, was the most dramatic finding of the study.

“Because the study is so large, we were able to look at so many individual cancer sites,” she says. “Some of these cancers are rarer than others, but because we had so many people we could study them, too.”

While she is not surprised by the link between weight and cancer, Calle notes that the wide range of cancers linked was unexpected. “It’s more the rule than the exception,” she says.

However, some cancers – such as brain, bladder, melanoma and lung – did not appear linked.

Obesity raises the amount of estrogen in the blood, it increases acid reflux, and it raises insulin levels, which in turn results in more cell division. Obesity also makes it more difficult to diagnose and treat cancer.

Too few lose weight

If gaining weight increases the risk of cancer, would losing weight decrease it?

Sadly, Calle says, it is difficult to find subjects for such a study because people who lose weight tend to gain it back. “We can study people who quit smoking,” Calle says, “but we do not have a lot of people who lose weight and keep it off.”

She assumes that losing weight would reduce the risk, though, because losing weight does reduce the hormonal activity — insulin levels drop, as do hormone levels and blood pressure.

“The hormonal levels decrease with weight loss,” Calle says. “When you lose weight, insulin levels go down quickly.”

But losing weight or even maintaining a healthy weight is — pardon the pun — a growing problem for Americans.

“Only 35 percent of adults are of a normal weight; 65 percent of adults are overweight. We just keep accommodating it and accommodating our perception of what is normal,” Calle says.

Calle knows how hard that struggle is. “I work very hard to maintain what is on the high end of normal,” she says. “I’m not a ‘skinny-minnie.'” But a more sedentary lifestyle, increasing child obesity, dependence on the car, and time pressures that mean fast food for dinner again shape our culture – and our waistlines.

“The first step is a different mindset,” Calle says. “We have to begin to equate normal weight with a state of health. We’ve kind of gotten there with smoking – even people who do smoke don’t want to be smoking, and they don’t want their kids to smoke.”

“People will need to demand a world that makes it easier to stay at an appropriate weight,” Calle says. “We want decent stairwells so that we can take the stairs at work,” she says. “We don’t want just vending machines full of crap. We have to change our cultural norms if we’re going to get a hold of this.”