Diet and Fat: A Severe Case of Mistaken Consensus

And another fraud -- Ancel Keys -- who received great honours

In 1988, the surgeon general, C. Everett Koop, proclaimed ice cream to a be public-health menace right up there with cigarettes. Alluding to his office's famous 1964 report on the perils of smoking, Dr. Koop announced that the American diet was a problem of "comparable" magnitude, chiefly because of the high-fat foods that were causing coronary heart disease and other deadly ailments.

He introduced his report with these words: "The depth of the science base underlying its findings is even more impressive than that for tobacco and health in 1964". That was a ludicrous statement, as Gary Taubes demonstrates in his new book meticulously debunking diet myths, "Good Calories, Bad Calories" (Knopf, 2007). The notion that fatty foods shorten your life began as a hypothesis based on dubious assumptions and data; when scientists tried to confirm it they failed repeatedly. The evidence against Haagen-Dazs was nothing like the evidence against Marlboros.

It may seem bizarre that a surgeon general could go so wrong. After all, wasn't it his job to express the scientific consensus? But that was the problem. Dr. Koop was expressing the consensus. He, like the architects of the federal "food pyramid" telling Americans what to eat, went wrong by listening to everyone else. He was caught in what social scientists call a cascade.

We like to think that people improve their judgment by putting their minds together, and sometimes they do. The studio audience at "Who Wants to Be a Millionaire" usually votes for the right answer. But suppose, instead of the audience members voting silently in unison, they voted out loud one after another. And suppose the first person gets it wrong.

If the second person isn't sure of the answer, he's liable to go along with the first person's guess. By then, even if the third person suspects another answer is right, she's more liable to go along just because she assumes the first two together know more than she does. Thus begins an "informational cascade" as one person after another assumes that the rest can't all be wrong.

Because of this effect, groups are surprisingly prone to reach mistaken conclusions even when most of the people started out knowing better, according to the economists Sushil Bikhchandani, David Hirshleifer and Ivo Welch. If, say, 60 percent of a group's members have been given information pointing them to the right answer (while the rest have information pointing to the wrong answer), there is still about a one-in-three chance that the group will cascade to a mistaken consensus.

Cascades are especially common in medicine as doctors take their cues from others, leading them to overdiagnose some faddish ailments (called bandwagon diseases) and overprescribe certain treatments (like the tonsillectomies once popular for children). Unable to keep up with the volume of research, doctors look for guidance from an expert - or at least someone who sounds confident.

In the case of fatty foods, that confident voice belonged to Ancel Keys, a prominent diet researcher a half-century ago (the K-rations in World War II were said to be named after him). He became convinced in the 1950s that Americans were suffering from a new epidemic of heart disease because they were eating more fat than their ancestors. There were two glaring problems with this theory, as Mr. Taubes, a correspondent for Science magazine, explains in his book. First, it wasn't clear that traditional diets were especially lean. Nineteenth-century Americans consumed huge amounts of meat; the percentage of fat in the diet of ancient hunter-gatherers, according to the best estimate today, was as high or higher than the ratio in the modern Western diet. Second, there wasn't really a new epidemic of heart disease. Yes, more cases were being reported, but not because people were in worse health. It was mainly because they were living longer and were more likely to see a doctor who diagnosed the symptoms.

To bolster his theory, Dr. Keys in 1953 compared diets and heart disease rates in the United States, Japan and four other countries. Sure enough, more fat correlated with more disease (America topped the list). 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. (And, as Mr. Taubes notes, no one would have puzzled over the so-called French Paradox of foie-gras connoisseurs with healthy hearts.)

The evidence that dietary fat correlates with heart disease "does not stand up to critical examination," the American Heart Association concluded in 1957. 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.

The association's report was big news and put Dr. Keys, who died in 2004, on the cover of Time magazine. The magazine devoted four pages to the topic - and just one paragraph noting that Dr. Keys's diet advice was "still questioned by some researchers." That set the tone for decades of news media coverage. Journalists and their audiences were looking for clear guidance, not scientific ambiguity.

After the fat-is-bad theory became popular wisdom, the cascade accelerated in the 1970s when a committee led by Senator George McGovern issued a report advising Americans to lower their risk of heart disease by eating less fat. "McGovern's staff were virtually unaware of the existence of any scientific controversy," Mr. Taubes writes, and the committee's report was written by a nonscientist "relying almost exclusively on a single Harvard nutritionist, Mark Hegsted." 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."

Meanwhile, there still wasn't good evidence to warrant recommending a low-fat diet for all Americans, as the National Academy of Sciences noted in a report shortly after the U.S.D.A. guidelines were issued. But the report's authors were promptly excoriated on Capitol Hill and in the news media for denying a danger that had already been proclaimed by the American Heart Association, the McGovern committee and the U.S.D.A.

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.

With skeptical scientists ostracized, the public debate and research agenda became dominated by the fat-is-bad school. Later the National Institutes of Health would hold a "consensus conference" that concluded there was "no doubt" that low-fat diets "will afford significant protection against coronary heart disease" for every American over the age of 2. The American Cancer Society and the surgeon general recommended a low-fat diet to prevent cancer.

But when the theories were tested in clinical trials, the evidence kept turning up negative. As Mr. Taubes notes, the most rigorous meta-analysis of the clinical trials of low-fat diets, published in 2001 by the Cochrane Collaboration, concluded that they had no significant effect on mortality.

Mr. Taubes argues that the low-fat recommendations, besides being unjustified, may well have harmed Americans by encouraging them to switch to carbohydrates, which he believes cause obesity and disease. He acknowledges that that hypothesis is unproved, and that the low-carb diet fad could turn out to be another mistaken cascade. The problem, he says, is that the low-carb hypothesis hasn't been seriously studied because it couldn't be reconciled with the low-fat dogma.

Mr. Taubes told me he especially admired the iconoclasm of Dr. Edward H. Ahrens Jr., a lipids researcher who spoke out against the McGovern committee's report. Mr. McGovern subsequently asked him at a hearing to reconcile his skepticism with a survey showing that the low-fat recommendations were endorsed by 92 percent of "the world's leading doctors."

"Senator McGovern, I recognize the disadvantage of being in the minority," Dr. Ahrens replied. Then he pointed out that most of the doctors in the survey were relying on secondhand knowledge because they didn't work in this field themselves. "This is a matter," he continued, "of such enormous social, economic and medical importance that it must be evaluated with our eyes completely open. Thus I would hate to see this issue settled by anything that smacks of a Gallup poll." Or a cascade.

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Cell transplant 'can ease slipped disc pain'

The results so far are not very impressive, however

A new treatment for slipped discs reduces pain, improves mobility and cuts the likelihood of further surgery, research revealed yesterday. Two years after undergoing the procedure, which involves injecting soft tissue cells into damaged discs, patients had less than a third of the pain they experienced beforehand. They reported 20 per cent less pain than those who had standard slipped disc operations and greater ability to move and function normally, according to the study.

There are around 14 million consultations with doctors about back pain in Britain every year. More than 20,000 operations a year are carried out for degenerative back problems such as slipped discs in England.

Vertebral discs form the cushioning and connecting material between the 24 vertebrae that make up the spine. Ageing or injury can cause the cartilage that makes up the outer wall of the disc to tear, allowing the soft inner part to bulge out - known as a slipped disc herniation. The escaped soft tissue can press against and potentially damage sensitive nerves, causing back and leg pain. In serious cases an operation is needed to remove material, relieving pressure on spinal nerve tissue.

However, the loss of the tissue leads to reduced disc height and shock absorption. Some 70 per cent of patients are left with continued pain and around one in 10 faces further surgery.

The new treatment - autologous disc-derived chondrocyte transplantation (ADCT) - involves growing soft tissue cells from the removed material, which are later re-injected into the damaged disc. The aim is to return the disc to its former size and health to delay the degeneration that usually follows a slipped disc. The procedure was developed at Co.don, a biotechnology company based near Berlin in Germany.

Researchers compared the experiences of 120 patients who had the treatment with 120 who had traditional surgery. The full study will only be completed five years after all patients had their operations, however interim results are available for 52 patients who were questioned two years after treatment. Those who had the new treatment reported 20 per cent less pain and a third less disability than those who had conventional surgery. They also reported having an average of 30 per cent of the pain they had been experiencing.

Jeremy Fairbank, professor of spinal surgery at the Nuffield Orthopaedic Centre in Oxford, said he would be sceptical until the full results of a large-scale clinical trial were published. He said: "Cell death occurs as part of disc degeneration and I am not convinced that the new cells that are injected in will be any more likely to survive."

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Just some problems with the "Obesity" war:

1). It tries to impose behavior change on everybody -- when most of those targeted are not obese and hence have no reason to change their behaviour. It is a form of punishing the innocent and the guilty alike. (It is also typical of Leftist thinking: Scorning the individual and capable of dealing with large groups only).

2). The longevity research all leads to the conclusion that it is people of MIDDLING weight who live longest -- not slim people. So the "epidemic" of obesity is in fact largely an "epidemic" of living longer.

3). It is total calorie intake that makes you fat -- not where you get your calories. Policies that attack only the source of the calories (e.g. "junk food") without addressing total calorie intake are hence pissing into the wind. People involuntarily deprived of their preferred calorie intake from one source are highly likely to seek and find their calories elsewhere.

4). So-called junk food is perfectly nutritious. A big Mac meal comprises meat, bread, salad and potatoes -- which is a mainstream Western diet. If that is bad then we are all in big trouble.

5). Food warriors demonize salt and fat. But we need a daily salt intake to counter salt-loss through perspiration and the research shows that people on salt-restricted diets die SOONER. And Eskimos eat huge amounts of fat with no apparent ill-effects. And the average home-cooked roast dinner has LOTS of fat. Will we ban roast dinners?

6). The foods restricted are often no more calorific than those permitted -- such as milk and fruit-juice drinks.

7). Tendency to weight is mostly genetic and is therefore not readily susceptible to voluntary behaviour change.

8). And when are we going to ban cheese? Cheese is a concentrated calorie bomb and has lots of that wicked animal fat in it too. Wouldn't we all be better off without it? And what about butter and margarine? They are just about pure fat. Surely they should be treated as contraband in kids' lunchboxes! [/sarcasm].

Trans fats:

For one summary of the weak science behind the "trans-fat" hysteria, see here. Trans fats have only a temporary effect on blood chemistry and the evidence of lasting harm from them is dubious. By taking extreme groups in trans fats intake, some weak association with coronary heart disease has at times been shown in some sub-populations but extreme group studies are inherently at risk of confounding with other factors and are intrinsically of little interest to the average person.

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