This week, CNN’s Paul Begala fell prey to one of the most over-hyped, and admittedly erroneous fat myths — that obesity supposedly kills 400,000 Americans a year. This blunder came Wednesday, when the Center for Consumer Freedom joined Center for Science in the Public Interest (CSPI) Executive DirectorMichael Jacobson on CNN’s Crossfire to debate the Cleveland Clinic’s recent announcement that it would try to evict McDonald’s from its premises.We thought we’d heard it all when CSPI’s Jacobson said that he wouldn’t "mind taking money from trial lawyers" and praised them for "fighting for the public good." But then Begalaturned to us and asked:
BEGALA: One of your reports was titled "An Epidemic of Obesity Myths." Well, with the government reporting 400,000 people a year dying because they’re too fat, is that really a myth?CCF: Yes, it is…
Like so many others, Begala mistakenly reiterated one of the most common obesity myths. Last month the CDC was forced to admit that its often-quoted "400,000 deaths" statistic was drastically exaggerated by a simple mathematical error. Meanwhile, leading CDC researchers are attacking the underlying methodology used to generate the 400,000 figure.The CDC’s 400,000 number is based on a previous study published in JAMA (the Journal of the American Medical Association) by financially conflicted University of Alabama Professor Dr. D.B. Allison. He estimated that 300,000 people supposedly died due to obesity in 1990. But even before the CDC’s follow-up report was published — saying the number had inflated to 400,000 in 2000 — a group of CDC researchers called Allison’s study (and by implication the CDC’s) into question.In a recent study published in the American Journal of Public Health, a group of CDC researchers found that Allison overestimated the number of deaths attributable to obesity because the risk substantially decreases with age. Specifically commentating on Allison’s work, they wrote: "we observed over a 10-fold difference in the magnitude of the estimates, from 23,313 to 297,835 deaths, depending on age specific mortality relative risks." The article ultimately concludes:
Given the 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 of the number of deaths attributable to obesity.
A second study by an overlapping team of CDC researchers found that Allison’s original study overestimated the total number of obesity-related deaths by at least 17 percent — and probably much more — by not properly accounting for the influence of either age and sex. Writing in the American Journal of Epidemiology they found:
The method used by Allison et al… is contradicted by several published statistical papers, which show that such an approach can lead to bias.
Using Allison’s method, they wrote, that "overestimation of deaths attributable to overweight and obesity in the US population is more likely than underestimation." Even assuming that everything else Allison did was correct — which it wasn’t — the authors point out that more than half the deaths occured among people over 75 years old: "If we restrict attention to deaths occurring in people under 75 years of age, the estimated number of deaths due to obesity would be considerably smaller."