Cascading into a Crusade Against Dietary Fat

In the first hour of today's Rush Limbaugh show, he discussed a column by John Tierney called "Diet and Fat: A Severe Case of Mistaken Consensus". It's a very interesting article about the main idea of Gary Taubes's new book Good Calories, Bad Calories: that eating fat isn't bad.

The article showed how scientific consensus can come to a faulty conclusion due to a phenomenon known to social scientists as a "cascade": a confident voice can lead others in the wrong direction like sheep that have gone astray. In 1953, Dr. Ancel Keys showed a correlation between how much fat people from a particular country ate vs. how much heart disease was in the population. ("But critics at the time noted that if Dr. Keys had analyzed all 22 countries for which data were available, he would not have found a correlation.") In 1957, the American Medical Association didn't find Dr. Keys' evidence convincing. But Dr. Keys didn't give up his efforts to get his theory support:

But three years later the association changed position — not because of new data, Mr. Taubes writes, but because Dr. Keys and an ally were on the committee issuing the new report. It asserted that “the best scientific evidence of the time” warranted a lower-fat diet for people at high risk of heart disease.

Years later, a Senate committee issued a report written by a non-scientist that relied "almost exclusively" on one particular nutritionist.

That report impressed another nonscientist, Carol Tucker Foreman, an assistant agriculture secretary, who hired Dr. Hegsted to draw up a set of national dietary guidelines. The Department of Agriculture’s advice against eating too much fat was issued in 1980 and would later be incorporated in its “food pyramid.”

Tierney also explained how as politicians became more convinced that the science was irrefutable, scientists began to risk their reputations if they questioned the "fat is bad" theory:

The scientists, despite their impressive credentials, were accused of bias because some of them had done research financed by the food industry. And so the informational cascade morphed into what the economist Timur Kuran calls a reputational cascade, in which it becomes a career risk for dissidents to question the popular wisdom.

John Tierney also has a follow-up article about this topic: How the Low-Fat, Low-Fact Cascade Just Keeps Rolling Along