Just when they probably thought things couldn’t get any worse,the cabal of "obesity warriors" on a crusade to hype fear of fat has taken yet another blow. An article in Scientific American titled "Obesity: An Overblown Epidemic?" untangles the shoddy, agenda-driven research behind the so-called "obesity epidemic." The article begins: "A growing number of dissenting researchers accuse government and medical authorities — as well as media — of misleading the public about the health consequences of rising body weights."The article continues:

[Dissenting scientists] allege, however, that experts are blowing hot air when they warn that overweight and obesity are causing a massive, and worsening, health crisis. They scoff, for example, at the 2003 assertion by Julie L. Gerberding, director of the Centers for Disease Control and Prevention, that "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 terms of the health impact on our country and our society." (An epidemic of influenza killed 40 million people worldwide between 1918 and 1919, including 675,000 in the U.S.)

In addition to extensive reporting on the "dubious assumptions, statistical errors and outdated measurements" used to calculate the CDC’s 400,000 obesity-related deaths estimate (more on that next week), the article also investigates a headline-grabbing "Special Report" published in The New England Journal of Medicine claiming that obesity will eventually cost Americans 2 to 5 years of life expectancy. We debunked that article when it came out. And Science magazine reported earlier this month:

[The study’s lead author S. Jay] Olshansky now says that in light of Flegal’s recent paper on obesity deaths and a companion paper that she, Williamson, and other CDC scientists authored in the same issues of JAMA, his life expectancy forecasts might be inaccurate.

Now Scientific American reports that another co-author of the study is also backing away from its conclusions. (That co-author just happens to be Dr. D.B. Allison, the financially-conflicted researcher who came up with the method the CDC used to generate its bogus 400,000 number.) Regarding the life expectancy study, Scientific Americanreports:

"These are just back-of-the-envelope, plausible scenarios," Allison hedges, when pressed. "We never meant for them to be portrayed as precise." Although most media reports jumped on the "two to five years" quote, very few mentioned that the paper offered no statistical analysis to back it up.

So another obesity myth down the drain. For the technically inclined,Scientific American goes on to dissect the flawed study on life expectancy:

The life expectancy costs of obesity that Olshansky and his colleagues actually calculated were based on a handful of convenient, but false, presuppositions. First, they assumed that every obese American adult currently has a BMI of 30, or alternatively of 35 — the upper and lower limits of the "mild obesity" range. They then compared that simplified picture of the U.S. with an imagined nation in which no adult has a BMI of more than 24 — the upper limit of "healthy weight" — and in which underweight causes zero excess deaths.

To project death rates resulting from obesity, the study used risk data that are more than a decade old rather than the newer ratios Flegal included, which better reflect dramatically improved treatments for cardiovascular disease and diabetes. The authors further assumed not only that the old mortality risks have remained constant but also that future advances in medicine will have no effect whatsoever on the health risks of obesity.

If all these simplifications are reasonable, the March paper concluded, then the estimated hit to the average life expectancy of the U.S. population from its world-leading levels of obesity is four to nine months. ("Two to five years" was simply a gloomy guess of what could happen in "coming decades" if an increase in overweight children were to fuel additional spikes in adult obesity.) The study did not attempt to determine whether, given its many uncertainties, the number of months lost was reliably different from zero. Yet in multiple television and newspaper interviews about the study, coauthor David S. Ludwig evinced full confidence as he compared the effect of rising obesity rates to "a massive tsunami headed toward the United States."