The rhetoric surrounding the so-called “obesity epidemic” has itself reached epidemic proportions. At the center of the debate is a study conducted by a team of researchers from the Centers for Disease Control and Prevention that led to the myth that obesity causes 400,000 deaths annually. In little more than a year, the CDC’s much-touted study has come unraveled. Here is a timeline of the study’s incremental demise.
March 10, 2004 — Despite internal dissent at the CDC, JAMA publishes the 400,000-deaths study.
May 7, 2004 — Science magazine reports that even before publication, “some researchers, including a few at CDC, dismiss [the CDC’s 400,000 deaths statistic], saying the underlying data are weak.” The article reads in part:
Some researchers, including a few at CDC, dismiss this prediction, saying the underlying data are weak. They argue that the paper’s compatibility with a new antiobesity theme in government public health pronouncements — rather than sound analysis — propelled it into print … [Some argue that] the new numbers on obesity are weak — or as one critic in CDC says, “loosey-goosey.” … Several epidemiologists at CDC and the National Institutes of Health (NIH) echoed [concerns about statistical biases that inflated the deaths associated with obesity] but declined to speak on the record. “I don’t want to lose my job,” said one CDC staffer who does research in the area. Critics also object that the authors added an arbitrary number of deaths from poor nutrition (15,000) to the obesity category. A CDC scientist says internal discussions on these issues got “very contentious” months before publication and left some feeling that the conclusions were not debatable.
June 2, 2004 — The Center for Consumer Freedom releases “An Epidemic of Obesity Myths” debunking the 400,000 deaths figure, along with a number of other myths surrounding the obesity debate.
June 21, 2004 — Congressman Henry Waxman (D-CA) requests a Government Accountability Office investigation of the CDC’s death estimate for obesity.
June 23, 2004 — CDC National Center for Chronic Disease Prevention and Health Promotion acting director Dr. George Mensah asks the CDC’s Dr. Stephen Thacker to conduct an internal review of the 400,000-deaths study.
August 15, 2004 — CDC researchers Katherine Flegal and David Williamson and National Institutes of Health researcher Barry Graubard co-author a paper in the American Journal of Epidemiology critiquing the method used in the CDC’s original paper. The authors conclude:
Existing estimates of the number of deaths attributed to overweight and obesity were calculated by using a method likely to produce biased estimates, when the effects of obesity vary by age or other characteristics. Estimates of deaths attributable to overweight and obesity arrived at by using this approach may be biased and should be viewed cautiously.
A second paper, published in the American Journal of Public Health by Flegal, Williamson and two other CDC researchers, also criticizes the 400,000-deaths paper’s methods. The authors warn:
Our examination suggests that given present knowledge about the epidemiology of obesity, and especially the impact of age on mortality risks associated with obesity, it may be difficult to develop accurate and precise estimates. We urge caution in the use of current estimates on the number of deaths attributable to obesity and also urge researchers to devote greater efforts to improve the data and methods used to estimate this important public health statistic.
Significantly, both studies were submitted for publication in 2003, months before the 400,000-deaths study appeared in JAMA.
November 8, 2004 — The Newark Star-Ledger reports that CDC Director Julie Gerberding once compared obesity to the Black Death:
“If you looked at any epidemic — whether it’s influenza or plague from the Middle Ages — they are not as serious as the epidemic of obesity in the terms of the health impact on our country and our society.”
November 23, 2004 — The Wall Street Journal publishes a front-page story on errors in the 400,000-deaths study. The article reads in part:
A widely quoted federal study that concluded obesity is poised to overtake tobacco as the leading cause of preventable death inflated the impact of obesity on the annual death toll by tens of thousands due to statistical errors … Even before the disputed study was published, several scientists at the CDC expressed misgivings to their superiors about its methodology and findings, according to documents and people familiar with the debate … “I am worried that the scientific credibility of CDC likely could be damaged by the manner in which this paper and valid, credible, and repeated scientific questions about its methodology have been handled,” wrote Terry Pechacek, associate director for science in the CDC ‘s Office on Smoking and Health, in an April 30 e-mail shortly after the study was published. Dr. Pechacek wrote to colleagues that he had warned two of the paper’s authors, as well as another senior scientist, “I would never clear this paper if I had been given the opportunity to provide a formal review.”
December 3, 2004 — A follow-up article in The Wall Street Journal revealed additional problems with the CDC’s methodology:
Critics of the study say the estimate was inflated not just by the statistical mistakes the CDC acknowledged last week, but also by the authors’ scientific approach. The number of obesity-related deaths could be less than half of the 400,000 estimated in the flawed CDC study, according to some scientists familiar with the debate.
University of Alabama professor David Allison, who originally developed the methodology used in the CDC study, admits in the story that measuring obesity-attributable deaths “is an evolving science.”
January 18, 2005 — The CDC published an erratum in JAMA admitting to a mathematical error. The estimate of deaths is lowered to 365,000 per year.
February 9, 2004 — A summary report of the CDC’s internal review committee is buried on the agency’s website.. It concludes that the underlying methodology used to estimate obesity-attributable deaths had significant limitations:
The paper published by Mokdad, et al., Actual Causes of Death in the United States, 2000, has provoked significant controversy both inside and outside the agency. While there was at least one error in the calculations and both the presentation of the paper and limitations of the approach could have been expressed more clearly, the fundamental scientific problem centers around the limitations in both the data and the methodology in this area. (emphasis added)
The report also notes:
The scientists expressed concerns and did meet with some of the authors but they were not convinced that their perspectives were listened to or that requests for data were acknowledged.
February 25, 2005 — Responding to an op-ed by the Center for Consumer Freedom calling on the CDC to retract its embattled study, CDC Chief of Science Dixie Snider writes in the Atlanta Journal Constitution: “…we cannot and should not let this discussion of scientific methodology detract from the real issue.”
According to the CDC’s website, Snider’s job is “maintaining the integrity and productivity of CDC’s scientists by resolving controversial scientific issues.” Despite the fanfare with which the CDC announced its original finding of 400,000 deaths, Snider adds, “we should not let the focus on deaths attributable to obesity distract us from this serious health issue.”
February 28, 2005 — Following Snider’s astounding comments, the editorial board of The Washington Times joins CCF in calling on the CDC to publicly retract the flawed study. Describing Snider’s derision of science as “dangerous reasoning,” they write:
It’s clear that over the concerns of its own researchers the CDC shamefully pushed a scientifically flawed study to reach some politically correct end. Since then, it has not given contrary evidence publicity equal to the original report. Nothing less than a full retraction of the original study and an apology to the American people can amend these egregious mistakes.
April 20, 2005 — A team of researchers from the CDC and the NIH publish a bombshell study in JAMA attributing less than 26,000 deaths to obesity and overweight. The study stands in stark contrast to the CDC’s original estimate, which was fifteen times higher. CDC Chief of Science Dixie Snider says the agency won’t take a position on the new study because, “We’re too early in the science.”
April 22, 2005 — Opinion leaders across the country take the CDC to task for it’s handling of the obesity-death estimate. The editorial board of The New York Times opines:
[The new study’s] estimate has exploded like a bombshell amid the health officials struggling to control the undeniable upsurge of obesity here and abroad. It leaves the C.D.C., in particular, with a lot of explaining to do … The C.D.C. needs to say, loud and clear, whether it believes the estimates. The whole notion of what constitutes normal weight and overweight may have to be rethought.