Researchers from Harvard’s School of Public Health and decision makers at the Centers for Disease Control and Prevention (CDC) have launched separate campaigns to downplay and undermine a recent study, led by CDC researcher Katherine Flegal, attributing 25,814 deaths to overweight and obesity. The CDC had previously said the number was 400,000, more than fifteen times higher.
These efforts come in spite of a near-consensus that Flegal’s study, published in JAMA, surpasses all previous work in the field. Science magazine reported last month: “Scientists agree that Flegal’s study is superior.” CDC’s Donna Stroup, a co-author of the original 400,000 study, admits the Flegal study is “a step forward.”
Nonetheless, on May 26 a group of researchers from Harvard — each with a long history of hyping the problem of obesity — held a “symposium” to critique the supposedly “flawed” Flegal study. No one bothered to mention at the event that Dr. Flegal and her colleagues anticipated and addressed Harvard’s criticisms in their original article. The scientifically inclined can click here to read more about the Harvard critique and why it doesn’t hold water.
A week after the Harvard symposium, CDC director Julie Gerberding held a press conference aimed at “clearing up the confusion” about obesity. In essence, she urged the public to ignore the Flegal study and continue thinking of obesity as a raging “epidemic.” Headlines like “CDC apologizes for mixed messages on obesity” and “CDC weighs in again: Extra pounds not OK” were the result.
Below you will find the CDC’s primary excuses for downplaying the Flegal study, and why they amount to little more than misdirection.
CDC Claim: We shouldn’t focus so much on obesity-related deaths.
Writing in the Atlanta Journal-Constitution, CDC’s Dixie Snider argued: “We should not let the focus on deaths attributable to obesity distract us from this serious health issue.” Echoing Snider’s comments, USA Today reported:
The debate about the number of deaths “is not where the discussion ought to be,” says Bill Dietz, director of the CDC’s division of nutrition and physical activity. “To me, the issue is that the diseases associated with obesity are impairing people’s quality of life and contributing to the steady rise in medical costs.”
The CDC has, to put it mildly, changed its tune on the importance of obesity deaths. In March 2004, when the CDC released the original 400,000 deaths study, agency director Gerberding told a crowded press conference: “The fact that more than a third of deaths in America each year are related to smoking, poor eating habits and physical inactivity is both tragic and unacceptable.” In subsequent months, the “obesity kills” mantra quickly became the central theme of the agency’s public statements on obesity. Gerberding herself used the 400,000-deaths estimate in Congressional testimony to justify the agency’s $6.9 billion budget request. It was the only obesity-related statistic she used during her testimony.
An internal CDC memorandum, written by Gerberding and the other authors of the 400,000 deaths study, reveals what the agency really thinks about the importance of measuring obesity-related mortality:
Although significant scientific questions remain about how best to assess the actual causes of death, it remains a public health priority to identify those deaths that could be prevented or delayed substantially in the population.
CDC Claim: The science of measuring obesity-attributable deaths is still evolving.
It is of course true that science is evolving. But it’s a bit hard to believe the CDC’s claim that “we’re too early in the science” to take a position on the number of obesity-related deaths. It certainly didn’t have this concern when it engaged in a massive publicity campaign surrounding the 400,000 deaths number. At the time, the CDC chose to ignore significant problems with that statistic. Internal CDC documents indicate that the agency knew it was using the “wrong formula.”
CDC Claim: We were merely updating an old obesity-death study, not developing a new method of measurement.
To justify using an outdated and highly controversial methodology, the CDC claims that it was simply updating a study from 1993, which estimated the number of deaths from poor diet and physical inactivity at 300,000 annually. Commenting on the “considerable media coverage” and “letters from some scientists about our methods and assumptions,” CDC’s Stroup explained in an Institute of Medicine publication that the 400,000 deaths study, “was a classic replication study: its methodology was largely similar to that of the earlier study, in order to allow for comparisons of the 1990 and 2000 estimates.”
But the 400,000 estimate did not use the methodology of the 1993 paper. It relied on an entirely different method developed in 1999 by the University of Alabama’s David Allison. According to recently released internal CDC documents:
At the time this study was being conducted, the scientific literature had several papers describing potential bias. Following Allison et al in using an incorrect method was not justified. From the cross-clearance, it seems as if this bias from the wrong formula was pointed out to the authors.
CDC Claim: This is just one study to measure obesity-related deaths. It is not definitive.