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Obesity linked to 8 more types of cancer

REUTERS/Rick Wilking
An estimated 640 million adults and 110 million children are now obese.

More than a decade ago, after conducting a comprehensive review of the scientific evidence at that time, an international team of researchers reported that excess weight was linked to higher risks of five cancers: colon, esophagus, kidney, breast and uterus.

That same group of researchers — convened by the World Health Organization’s International Agency for Cancer on Research (IARC) — now says the list needs to be expanded.

Significantly.

In a new analysis of the existing evidence, published Thursday in the New England Journal of Medicine (NEJM), the researchers identify eight additional cancers linked to excess weight and obesity: stomach, liver, gall bladder, pancreas, ovary, thyroid, meningioma (a type of brain tumor) and multiple myeloma (a type of blood cancer).

“The burden of cancer due to being overweight or obese is more extensive than what has been assumed,” said Dr. Graham Colditz, a cancer-prevention specialist at the Washington University School of Medicine in St. Louis and chair of the IARC research team, in a released statement. “Many of the newly identified cancers linked to excess weight haven’t been on people’s radar screens as having a weight component.” 

A global problem

Obesity is generally determined by body mass index (BMI). Overweight is defined as a BMI of 25.0 to 29.9, and obesity as a BMI of 30 or more. (Yes, the BMI method of determining a healthy weight is not accurate in every case, but it’s generally considered “a good proxy for assessing overall body fatness,” as the authors of the new analysis point out.)

The rapidity with which the world is becoming obese is stunning. An estimated 640 million adults and 110 million children are now obese. That’s six times as many adults and twice as many children as four decades ago.

In fact, more people today are overweight or obese than are underweight.

In the United States, 38 percent of adults aged 20 and older are considered obese, according to the Centers for Disease Control and Prevention (CDC). 

Last year, the U.S. passed a distressing milestone: More Americans are now obese than overweight.

The toll on health is enormous. Globally, about 4.5 million deaths are caused by overweight and obesity each year, according to a study published earlier this year in the journal Cancer Epidemiology.

Many of those are cancer deaths. The Cancer Epidemiology study estimated, for example, that 9 percent of cancers developed among women in North America, Europe and the Middle East are linked to obesity.

Up to 13 cancers

In the new IARC analysis, which involved examining more than 1,000 relevant epidemiologic studies, the highest risks associated with being overweight or obese were for uterine cancer and esophageal cancer (specifically, adenocarcinoma, which begins in the mucus-producing glandular cells of the esophagus).

When compared with people of normal weight, those with the highest BMI (40 or greater) were almost five times more likely to develop uterine cancer and almost seven times more likely to develop esophagus adenocarcinoma. 

For people in the highest BMI category, the increased relative risk for the other 11 cancers ranged from 10 percent (for multiple myeloma and postmenopausal breast cancer) to 80 percent higher (for cancers of the stomach, kidney and liver).

The analysis also found that the higher the BMI, the greater the risk — for some cancers, at least. For example, compared with normal-weight women, those with a BMI of 25 to 25.9 had a 50 percent higher relative risk for endometrial (uterine) cancer. That risk more than doubled when the BMI was between 30 and 34.9, and it more than quadrupled when it reached the 35 to 39.9 range. And for women with a BMI of 40 or greater, the risk climbed seven-fold.

Another wake-up call

The studies involved in this analysis were mostly observational ones, which means they cannot prove a direct link between excess weight and the development of cancer.

The authors of the current analysis point out, however, that excess fat is associated with an overproduction of various hormones, such as estrogen, testosterone and insulin, as well as with chronic inflammation — factors that may help explain its link to cancer.

But plenty of people who aren’t overweight or obese develop cancer, and many obese people never get the disease. So this study shouldn’t be used as way of “blaming” overweight people with cancer for their illnesses.

Still, as Colditz says: “This is another wake-up call. It’s time to take our health and our diet seriously.”

FYI: You’ll find an abstract of the IARC report on the NEJM website, but the full report is, unfortunately, behind a paywall.

Comments (3)

  1. Submitted by Greg Kapphahn on 08/25/2016 - 10:32 am.

    “Linked”?

    There seems to be a serious issue in this report,…

    and all those like it,…

    which confuse correlation with causation.

    Unless and until the mechanism(s) by which obesity “causes”

    cancer of the colon, esophagus, kidney, breast and uterus,…

    it’s every bit as likely that the obesity, itself, is a side effect of the cancer which is developing within the patient’s body.

    Cancers of the colon, esophagus and stomach (which I’m surprised they left out) can easily irritate the digestive system in ways which the patient experiences as increased appetite.

    Cancer of the kidneys can alter body chemistry in ways that increase excretion of certain blood salts and decrease excretion others leaving the patient with increased appetite as the body seeks to compensate.

    The reality is and always has been the correlation is NOT causation and lazy statistical analysis such as this report represents,…

    completely sidesteps the kind of research needed to actually do anyone any good.

    Believing that telling patients to lose weight without exploring the reasons for their eating habits and appetite,…

    and paying close attention to how they’re experiencing their “appetite,”….

    risks missing a lot reasons for those experiences of “appetite” that might very well kill the patient;…

    reasons which have been ignored because of reports like this which make the unsupported claim that the patient’s WEIGHT is the problem,…

    (not a symptom of a much more serious problem.)

    • Submitted by Susan Lesch on 08/25/2016 - 11:57 am.

      Hold on

      Mr. Kapphahn, Ms. Perry writes, “The studies involved in this analysis were mostly observational ones, which means they cannot prove a direct link between excess weight and the development of cancer.” She lists stomach cancer first in a long list. (I don’t know why you are surprised they left it out, because they didn’t.)

      Separately, CDC said this week, “By 2014, cancer had replaced heart disease as the leading cause of death in 22 states….”
      http://www.cnn.com/2016/08/24/health/leading-causes-of-death-2016-heart-disease-cancer/

  2. Submitted by Earle Fowler on 09/01/2016 - 06:06 am.

    I concur

    Not to put the focus on Mr. Kapphahn response……….but I think what Ms. Perry was pointing out is that proper, better, nutrition and a change of life style can and will aid people that have excess body fat. Body fat being the possible cultprit behind the possible avenue or venue in which certain types of caner cells hybernate. By pointing out that there is a greater % of cancer types that can possibly develops in a particular body type is extremely helpful. The article did conclude that cancer develops in all body types and the article was not drawing any conclusion about cancer as being directly connected with obesity/overweight…….

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