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Good Calories, Bad Calories book report / review

(originally posted to my now-defunct LiveJournal; I've also written a summary of Taubes's followup book, Why We Get Fat)

Good Calories, Bad Calories is a 2007 book by Gary Taubes examining the link between recent widespread dietary changes and "diseases of civilization" such as heart disease and obesity. While it's certainly possible to use the book to draw conclusions about what to eat and what not to eat, it can best be described as a history of the changes during the 20th century to the prevailing wisdom of what constitutes a healthy diet.

The book's thesis is easy to state: There is an overwhelming amount of evidence that diets high in protein and fat (including that of the saturated variety) are not correlated with increased rates of heart disease, cancer, or obesity, and actually provide beneficial effects. There is also a large body of research suggesting that diets high in carbohydrates (especially those of the easy-to-digest variety, such as white flour, white rice, and sugars like sucrose and high-fructose corn syrup) do increase these rates of disease. Researchers and public health officials have ignored studies with results that contradict the message they began pushing in the 1960s, namely, that these diseases are caused by increased consumption of fat or by gluttony and sloth.

The book's primary villain is perhaps Ancel Keys, a dietary researcher who established the Laboratory of Physiological Hygiene at the University of Minnesota. In the late 1940s, Keys helped debunk the belief held by some physicians that dietary cholesterol was responsible for heart disease by demonstrating that feeding men diets high or low in cholesterol made no difference to the cholesterol levels in their bloodstreams. After visiting Rome for a conference in 1951 and then interviewing members of the heart-disease-free general population of Naples and heart-disease-prone upper class, Keys drew the conclusion that fat consumption was the cause of heart disease.

In 1953, Keys claimed that comparisons of diet and heart-disease mortality in the U.S., Canada, Australia, England and Wales, Italy, and Japan showed a direct correlation between the two. Other researches disputed his claim, "noting that Keys had chosen only six countries for his comparison though data were available for twenty-two countries. When all twenty-two were included in the analysis, the apparent link between fat and heart disease vanished." (p.18) Taubes claims that this bias toward hypothesis-supporting evidence is prevalent in much of Keys's research.

In 1957, the American Heart Association opposed Ancel Keys on the diet-health issue. The AHA's fifteen-page report castigated researchers—including Keys, presumably—for taking "uncompromising stands based on evidence that does not stand up under critical examination." Its conclusion was unambiguous: "There is not enough evidence available to permit a rigid stand on what the relationship is between nutrition, particularly the fat content of the diet, and atherosclerosis and coronary heart disease."

Less than four years later, the evidence hadn't changed, but now a six-man ad-hoc committee, including Keys and Jeremiah Stamler, issued a new AHA report that reflected a change of heart. Released to the press in December 1960, the report was slightly over two pages long and had no references. Whereas the 1957 report had concluded that the evidence was insufficient to authorize telling an entire nation to eat less fat, the new report argued the opposite—"the best scientific evidence of the time" strongly suggested that Americans would reduce their risk of heart disease by reducing the fat in their diets, and replacing saturated fats with polyunsaturated fats. This was the AHA's first official support of Keys's hypothesis, and it elevated high cholesterol to the leading heart-disease risk. ...

After the AHA report hit the press, Time quickly enshrined Keys on its cover as the face of dietary wisdom in America. As Time reported, Keys believed that the ideal heart-healthy diet would increase the percentage of carbohydrates from less than 50 percent of calories to almost 70 percent, and reduce fat consumption from 40 percent to 15 percent. The Time cover story, more than four pages long, contained only a single paragraph noting that Keys's hypothesis was "still questioned by some researchers with conflicting ideas of what causes coronary disease." (p.20-1)

The vilification of fat picked up additional supporters in the following years. Taubes attributes much of the speed with which the fat hypothesis became widely accepted to differences in philosophy between the two camps — researchers skeptical of Keys's hypothesis believed that a rigorous, scientific approach was needed to determine the truth; supporters believed it critical to convince the public to change its behavior as soon as possible in the hopes of reducing the chances that currently-healthy people would fall victim to heart disease in the future. To accomplish this, they often simplified their advice to such a degree that it completely ignored well-established findings.

... Some of the most reliable facts about the diet-heart hypothesis have been consistently ignored by public-health authorities because they complicated the message, and the least reliable findings were adopted because they didn't. Dietary cholesterol, for instance, has an insignificant effect on blood cholesterol. It _might_ elevate cholesterol levels in a small percentage of highly sensitive individuals, but for most of us, it's clinically meaningless. (Decreasing cholesterol consumption from four hundred milligrams a day, the average American intake in the 1990s, to the three hundred milligrams a day recommended by the National Cholesterol Education Program would be expected to reduce cholesterol levels by 1 to 2 mg/dl, or a decrease of perhaps 1 percent.) Nonetheless, the advice to eat less cholesterol—avoiding egg yolks, for instance—remains gospel. Telling people they should worry about cholesterol in their blood but not in their diet has been deemed too confusing. (p.19)

Later in the book, many pages are devoted to debunking the idea that the body is governed by a simple "calories in - calories out = weight change" equation, where losing or gaining weight is a simple matter of modifying either or both of the left terms. The body is highly adaptable when faced with a surplus or deficit of calories or an increased or decreased demand for energy. It's more appropriate to view the body as manipulating appetite and available energy (by way of varying the metabolic rate) to maintain a target weight. In other words, if you eat less, you'll lack the energy to exercise; if you exercise more, your appetite will increase accordingly. Despite most studies comparing normal-weight and overweight people having found that the overweight typically eat fewer calories (per a National Academy of Sciences report, p.229-230), researchers and public health officials insist that excessive calorie consumption is the cause of obesity.

Over the past century, numerous studies have addressed this issue of how much more easily some of us fatten than others. In these studies, volunteers are induced to overeat to considerable excess for months at a time. The most famous such study was conducted by the University of Vermont endocrinologist Ethan Sims beginning in the late 1960s. Sims first used students for his experiments, but found it difficult to get them to gain significant weight. He then used convicts at the Vermont State Prison, who initially raised their food consumption to four thousand calories a day. They gained a few pounds, but then their weights stabilized. So they ate five thousand calories a day, then seven thousand (five full meals a day), then ten thousand, while remaining sedentary.

There were "marked differences between individuals in ability to gain weight," Sims reported. Of his eight subjects that went two hundred days on this mildly heroic regimen, two gained weight easily and six did not. One convict managed to gain less than ten pounds after thirty weeks of forced gluttony (going from 134 pounds to 143). When the experiment ended, all the subjects "lost weight readily," Sims said, "with the same alacrity," in fact, as that with which obese patients typically return to their usual weights after semi-starvation diets. Sims concluded that we're all endowed with the ability to adopt our metabolism and energy expenditure "in response to both over- and undernutrition," but some of us, as with any physiological trait, do it better than others. (p.272-3)

One of my favorite aspects of the book was how little it relies on describing the processes occurring within the body and how they're affected by changes in diet. While the endocrine system is interesting to read about, I came in with close to zero knowledge of it and would have to take on faith any claims made about its operation. Much more compelling are the hundreds of studies summarized by Taubes in the main text and then enumerated in the book's 112-page endnotes and bibliography. This isn't to say that the book doesn't explain the effects of dietary changes in detail — it does, but it waits a while to do so and doesn't rely on it to support its main claims.

Last modified on May 16, 2010.