December 18, 2009

"The low-fat diet seems to be unhealthy"

Philosopher Martin Cohen has an interesting piece on the "madness of crowds," with particular reference to Climategate. Worth reading, and this excerpt is pretty interesting also!

Times Higher Education - Beyond debate?:

...One of the best examples of cascade theory is that of the entirely false consensus that built up in the 1970s around the danger of "fatty foods". In fact, this consensus still exists, even though it has never had any scientific basis.

The theory can be traced back to a single researcher, Ancel Keys, who published a paper saying that Americans were suffering from "an epidemic" of heart disease because their diet was more fatty than their bodies were used to after thousands of years of evolution.

In 1953, Keys added additional evidence from a comparative study of the US, Japan and four other countries. Country by country, this showed that a high-fat diet coincided with high rates of heart disease.

Unfortunately for this theory, it turned out that prehistoric "traditional diets" were not especially low-fat after all - indeed, even the hunter-gatherers of yore, if they relied on eating their prey, would have had more fat in their diet than most people do today. As Science magazine pointed out, in the most relevant period of 100 years before the supposed "epidemic" of heart disease, Americans were actually consuming large amounts of fatty meat, so the epidemic followed a reduction in the amount of dietary fat Americans consumed - not an increase...

(continues below)

...Keys' country-by-country comparison had also been skewed, with countries that did not fit the theory (such as France and Italy with their oily, fatty cuisines) being excluded. The American Heart Association (AHA), considered to be the voice of experts, issued a report in 1957 stating plainly that the fats-cause-heart-disease claims did not "stand up to critical examination". The case for there being any such epidemic was dubious, too - the obvious cause of higher rates of heart disease was that people were living longer, long enough to develop heart disease. But it was too late: the cascade had started.

Three years later, the AHA issued a new statement, reversing its view. It had no new evidence but it did have some new members writing the report, in the form of Keys himself and one of his friends. The new report made the cover of Time magazine and was picked up by non-specialists at the US Department of Agriculture, who then asked a supporter of the theory to draw up "health guidelines" for them. Soon, scarcely a doctor could be found prepared to speak out against such an overwhelming "consensus", even if a few specialized researchers still protested. And all this was good enough for the highest medical officer in the US, the Surgeon General, in 1988 to issue a doom-laden warning about fat in foods, and claiming that ice-cream was a health menace on a par with tobacco smoking.

It was a pretty silly theory, and certainly not one based on good evidence. In fact, in recent years, in large-scale studies in which comparable groups have been put on controlled diets (low fat and high fat) a correlation has at last been found. It turns out that the low-fat diet seems to be unhealthy. But no one is quite sure why....
Posted by John Weidner at December 18, 2009 8:04 AM
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