The Obesity Code. Jason Fung

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СКАЧАТЬ all great stories need a villain, and dietary fat was cast into that role. Dietary fat was thought to increase the amount of cholesterol, a fatty substance that is thought to contribute to heart disease, in the blood. Soon, physicians began to advocate lower-fat diets. With great enthusiasm and shaky science, the demonization of dietary fat began in earnest.

      There was a problem, though we didn’t see it at the time. The three macronutrients are fat, protein and carbohydrates: lowering dietary fat meant replacing it with either protein or carbohydrates. Since many high-protein foods like meat and dairy are also high in fat, it is difficult to lower fat in the diet without lowering protein as well.

      So, if one were to restrict dietary fats, then one must increase dietary carbohydrates and vice versa. In the developed world, these carbohydrates all tend to be highly refined.

      Low Fat = High Carbohydrate

      This dilemma created significant cognitive dissonance. Refined carbohydrates could not simultaneously be both good (because they are low in fat) and bad (because they are fattening). The solution adopted by most nutrition experts was to suggest that carbohydrates were no longer fattening. Instead, calories were fattening. Without evidence or historical precedent, it was arbitrarily decided that excess calories caused weight gain, not specific foods. Fat, as the dietary villain, was now deemed fattening—a previously unknown concept. The Calories-In/Calories-Out model began to displace the prevailing “fattening carbohydrates” model.

      But not everybody bought in. One of the most famous dissidents was the prominent British nutritionist John Yudkin (1910–1995). Studying diet and heart disease, he found no relationship between dietary fat and heart disease. He believed that the main culprit of both obesity and heart disease was sugar.^{9, 10} His 1972 book, Pure, White and Deadly: How Sugar Is Killing Us, is eerily prescient (and should certainly win the award for Best Book Title Ever). Scientific debate raged back and forth about whether the culprit was dietary fat or sugar.

       THE DIETARY GUIDELINES

      THE ISSUE WAS finally settled in 1977, not by scientific debate and discovery, but by governmental decree. George McGovern, then chairman of the United States Senate Select Committee on Nutrition and Human Needs, convened a tribunal, and after several days of deliberation, it was decided that henceforth, dietary fat was guilty as charged. Not only was dietary fat guilty of causing heart disease, but it also caused obesity, since fat is calorically dense.

      The resulting declaration became the Dietary Goals for the United States. An entire nation, and soon the entire world, would now follow nutritional advice from a politician. This was a remarkable break from tradition. For the first time, a government institution intruded into the kitchens of America. Mom used to tell us what we should and should not eat. But from now on, Big Brother would be telling us. And he said, “Eat less fat and more carbohydrates.”

      Several specific dietary goals were set forth. These included

      •raise consumption of carbohydrates until they constituted 55 percent to 60 percent of calories, and

      •decrease fat consumption from approximately 40 percent of calories to 30 percent, of which no more than one-third should come

      from saturated fat.

      With no scientific evidence, the formerly “fattening” carbohydrate made a stunning transformation. While the guidelines still recognized the evils of sugar, refined grain was as innocent as a nun in a convent. Its nutritional sins were exonerated, and it was henceforth reborn and baptized as the healthy whole grain.

      Was there any evidence? It hardly mattered. The goals were now the nutritional orthodoxy. Everything else was heathen. If you didn’t toe the line, you were ridiculed. The Dietary Guidelines for Americans, a report released in 1980 for widespread public consumption, followed the recommendations of the McGovern report closely. The nutritional landscape of the world was forever changed.

      The Dietary Guidelines for Americans, now updated every five years, spawned the infamous food pyramid in all its counterfactual glory. The foods that formed the base of the pyramid—the foods we should eat every single day—were breads, pastas and potatoes. These were the precise foods that we had previously avoided to stay thin. For example, the American Heart Association’s 1995 pamphlet, The American Heart Association Diet: An Eating Plan for Healthy Americans, declared we should eat six or more servings of “breads, cereals, pasta and starchy vegetables (that) are low in fat and cholesterol.” To drink, “Choose . . . fruit punches, carbonated soft drinks.” Ahhh. White bread and carbonated soft drinks—the dinner of champions. Thank you, American Heart Association (AHA).

      Entering this brave new world, Americans tried to comply with the nutritional authorities of the day and made a conscious effort to eat less fat, less red meat, fewer eggs and more carbohydrates. When doctors advised people to stop smoking, rates dropped from 33 percent in 1979 to 25 percent by 1994. When doctors said to control blood pressure and cholesterol, there was a 40 percent decline in high blood pressure and a 28 percent decline in high cholesterol. When the AHA told us to eat more bread and drink more juice, we ate more bread and drank more juice.

      Inevitably, sugar consumption increased. From 1820 to 1920, new sugar plantations in the Caribbean and American South increased the availability of sugar in the U.S. Sugar intake plateaued from 1920 to 1977. Even though “avoid too much sugar” was an explicit goal of the 1977 Dietary Guidelines for Americans, consumption increased anyway until the year 2000. With all our attention focused on fat, we took our eyes off the ball. Everything was “low fat” or “low cholesterol,” and nobody was paying attention to sugar. Food processors, figuring this out, increased the added sugars in processed food for flavor.

      Refined grain consumption increased by almost 45 percent. Since carbohydrates in North America tended to be refined, we ate more and more low-fat bread and pasta, not cauliflower and kale.¹¹

      Success! From 1976 to 1996, the average fat intake decreased from 45 percent of calories to 35 percent. Butter consumption decreased 38 percent. Animal protein decreased 13 percent. Egg consumption decreased 18 percent. Grains and sugars increased.

      Until that point, the widespread adoption of the low-fat diet was completely untested. We had no idea what effect it would have on human health. But we had the fatal conceit that we were somehow smarter than 200,000 years of Mother Nature. So, turning away from the natural fats, we embraced refined low-fat carbohydrates such as bread and pasta. Ironically, the American Heart Association, even as late as the year 2000, felt that low-carbohydrate diets were dangerous fads, despite the fact that these diets had been in use almost continuously since 1863.

      What was the result? The incidence of heart disease certainly did not decrease as expected. But there was definitely a consequence to this dietary manipulation—an unintentional one. Rates of obesity, defined as having a body mass index greater than 30, dramatically increased, starting almost exactly in 1977, as illustrated by Figure 1.2.¹²

      Figure 1.2. Increase in obese and extremely obese United States adults aged 20–74.

      The abrupt increase in obesity began exactly with the officially sanctioned move toward a low-fat, high-carbohydrate diet. Was it mere coincidence? Perhaps the fault lay in our genetic makeup instead.

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       INHERITING OBESITY

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