By now you’ve all heard the news. Growing love-handles or having a little too much “junk in the trunk” will give us all cancer — or so the public-health gurus and their spin-meisters would have us believe. This latest mass hysteria is based on a study conducted by the American Cancer Society (ACS) and published in a recent issue of The New England Journal of Medicine. It’s a perfect example of what can happen when bad science (“according to the latest study…”) meets lazy journalists and an unwary public.
Predictably, the print media have already begun issuing mindless editorials — “Slim Down or Risk the Big C: Obesity Should Scare Everyone,” screamed The San Jose Mercury News — and Q-and-A stories intended to help overweight Americans avoid “dying from more than a dozen cancers.” Some scientists are calling this new ACS study “irrefutable” and “absolutely convincing.” A spokesman from the Harvard School of Public Health called it “really important” and claimed that “[w]e can unequivocally say 14 percent of cancer in men and 20 percent in women is due to being overweight and obesity.”
Irrefutable? Convincing? Unequivocal? Dying from more than a dozen cancers? Before we jump on the bandwagon, we thought actually reading the study was in order. Here’s what CNN’s sound bites aren’t telling you.
Lead researcher Eugenia Calle told a Reuters Health reporter that the equation for cancer risk is simple: “The more weight you have, the higher the risk.” But her own data don’t agree. Calle’s study reported 4.5 cancer deaths per 1,000 people in the so-called “healthy” weight range (anyone whose Body-Mass Index, or BMI, is between 18.5 and 24.9). But in the “overweight” weight range (BMI 25.0 to 29.9), she only found 4.4 cancer deaths per 1,000. “Overweight” people actually have an overall lower cancer risk than those in the government-approved “healthy” cohort. We checked the math — twice.
Some kinds of cancer, if Calle’s own numbers are to be believed, might be prevented by excess weight. So-called “inverse relationships” were found between obesity and brain cancer, lung cancer, leukemia, melanoma, and others.
The study reports that women in the very highest weight categories (those whose BMI is over 40) actually have a lower risk of cancer (5.22 deaths per 1,000) than the very slimmest men (5.78 per 1,000). Read that sentence again. What the study’s data actually show is that women who resemble Camryn Manheim or Roseanne Barr are less likely to die of cancer than men who look like actor David Spade or basketball’s Shawn Bradley.
Not a single person connected with this “research” had his or her height or weight measured by a doctor or nurse. Instead, the entire study used self-reporting questionnaires distributed by “volunteers” (read: not health professionals). Respondents were expected to know their current weight — down to the pound — and their exact weight one year earlier. The ACS study’s authors made no attempt to account for inaccuracies that could arise from this method of data collection.
In an editorial accompanying the study, a Harvard doctor and a Swedish epidemiologist expressed serious misgivings on two fronts. First, they write, “a biologic mechanism clearly linking overweight and obesity to forms of cancer … has eluded investigators.” [Translation #1: If we can’t show how obesity causes cancer-related deaths to increase, maybe it doesn’t at all.] Second, they speculate that “the apparent effect of overweight and obesity on mortality due to cancer” might simply reflect “the incidence of various types of cancer.” [Translation #2: If a study claims to show that overweight people are at greater risk for cancers of the kidneys, pancreas, and uterus, maybe the study is really just measuring how frequently those cancers occur — and nothing more.]
All in all, there’s still room to argue that overweight Americans are at moderate risk for any number of ailments. But this latest study simply doesn’t prove what your local talking-head says it proves.
It should be clear by now that obesity will be the next great public-health bugaboo (now that the tobacco industry has been bled dry). Eugenia Calle launched a telling salvo in USA Today last week. “We are at that the same point now with obesity,” Calle said, “that we were with smoking in the mid-’60s.” Calle, the ACS’s director of analytic epidemiology, also noted: “For smoking, we took action in a lot of different ways, including public education and policy and regulatory changes. It wasn’t just left up to the individual.”
And the same will soon be said of your food choices, if Calle’s cabal of cancer-scare artists has its way.
