Good Calories, Bad Calories

biking, power yoga, spinning, aerobics, and a host of other now relatively common physical activities had yet to be invented. To put this in numerical terms, this was an era when the revenues of the health-club industry were estimated at $200 million a year; in 2005, revenues were $16 billion, and nearly forty million Americans belonged to such clubs.^*68

Press reports also support this version of history. By 1977, the New York Times was discussing the “exercise explosion” that had come about because the conventional wisdom of the 1960s that exercise was “bad for you” had been transformed into the “new conventional wisdom—that strenuous exercise is good for you.” When the Washington Post estimated in 1980 that a hundred million Americans were now partaking in the “new fitness revolution,” it also noted that most of them “would have been derided as ‘health nuts’” only a decade earlier. “What we are seeing,” the Post suggested, “is one of the late twentieth century’s major sociological events.”

Another apparent contradiction of the notion that either sedentary behavior or prosperity or a toxic food environment is the cause of obesity is that obesity has always been most prevalent among the poorest and thus, presumably, harder-working members of society. In developed nations, the poorer people are, the heavier they’re likely to be. The NHANES studies confirmed this observation, first documented more than forty years ago. In 1965, Albert Stunkard and his colleagues at New York Hospital reported that they had surveyed 1,660 New Yorkers and found that obese women were six times more common at the lowest socioeconomic level than at the highest. Thirty percent of the poorest women were obese, compared with 16 percent of those of “middle status” and only 5 percent of the richest. The poor men were twice as likely to be obese as the rich (32 percent to 16 percent). These observations have been confirmed repeatedly throughout the world, in both children and adults. Because poor and immigrant populations are considerably less likely than wealthier, more established populations to own labor-saving devices, and because they are more likely to work in physically demanding occupations, that poverty is a risk factor for obesity is another compelling reason to question the notion that sedentary behavior is a cause.

There is a tendency among public-health authorities, obesity researchers, and health writers to discuss obesity as though the problem on a societal scale were only twenty or thirty years old, but this confuses the problem of obesity with the current obesity epidemic. Because these last few decades also coincide with the spread of McDonald’s and other global purveyors of high-fat fast foods, obesity can conveniently be blamed on fast food by virtue of this association. (It has also, by this same logic, been popularly blamed on high-fructose corn syrup.) But the research literature of obesity dates back further than the epidemic, and by including all of the relevant observations over the years, we can begin to rule out competing hypotheses. Any hypothesis that purports to explain how obesity is caused, after all, should explain the emergence of obesity in any population and at any time, not just the increasing obesity in the past few decades.

The Pima Indians of southwestern Arizona are now infamous for having the highest rates of obesity and diabetes in the United States. Today the standard explanation for obesity among the Pima is that they have succumbed, as we all have, to prosperity and the toxic environment of American life. Over the last century, the Pima supposedly experienced a nutrition transition—an exaggerated version of the changing-American-diet story. Farmers and hunters became relatively sedentary wage-earners, while their diet changed from one very low in fat and high in fiber-rich carbohydrates and vegetables to a modern high-fat, high-sugar American diet. “As the typical American diet became more available on the reservation after the [Second World] war,” according to an NIH report entitled The Pima Indians: Pathfinders for Health, “people became more overweight.” “If the Pima Indians could return to some of their traditions,” explained one NIH authority, “including a high degree of physical activity and a diet with less fat and more starch, we might be able to reduce the rate, and surely the severity, of unhealthy weight in most of the population.”

The problem with this version of the Pima history is that obesity and overweight had been evident a century ago, when the relevant nutrition transition was from relative abundance to extreme poverty. From November 1901 to June 1902, the Harvard anthropologist Frank Russell lived on the Pima reservation south of Phoenix studying the tribe and its culture. Many of the older Pima, Russell noted in a report of the Bureau of American Ethnology, “exhibit a degree of obesity that is in striking contrast with the ‘tall and sinewy’ Indian conventionalized in popular thought.”

Obesity among the Pima is not a new phenomenon, as demonstrated by this photo of “Fat Louisa” taken in 1901 or 1902 by the Harvard anthropologist Frank Russell.

Russell’s assessment of the Pima’s relative corpulence was then confirmed by the anthropologist and physician Ales Hrdlika, who visited the Pima reservation in 1902 and 1905. “Especially well- nourished individuals, females and also males, occur in every tribe and at all ages,” Hrdlika reported, “but real obesity is found almost exclusively among the Indians on reservations.”

For perhaps two millennia, the Pima had lived as both hunter-gatherers and agriculturalists. Game was abundant in the region, as were fish and clams in the Gila River. When the Jesuit missionary Eusebio Kino arrived among the Pima in 1787, the tribe was already raising corn and beans on fields irrigated with Gila River water. In the decades that followed, they took to raising cattle, poultry, wheat, melons, and figs. They also ate mesquite beans, the fruit of the saguaro cactus, and a mush of what Russell later called “unidentified worms.” In 1846, when a U.S. Army battalion passed through Pima lands, the battalion’s surgeon John Griffin described the Pima as “sprightly” and in “fine health.” He also noted that the Pima had “the greatest abundance of food, and take care of it well, as we saw many of their storehouses full of pumpkins, melons, corn &c.”

Life began to change dramatically the following year, when a wagon route was opened to California “by way of Tucson and the Pima villages.” This became the southernmost overland route for the California gold rush that began in 1849; tens of thousands of travelers passed through the Pima villages on the way west over the next decade. They relied on the Pima for food and supplies.

With the arrival of Anglo-American and Mexican settlers in the late 1860s, the prosperity of the Pima came to an end, replaced by what the tribe referred to as “the years of famine.” Over the next quarter-century, these newcomers hunted the local game almost to extinction, and the Gila River water, on which the Pima depended for fishing and irrigating their own fields, was “entirely absorbed by the Anglo settlements upstream.” By the mid- 1890s, the Pima were relying on government rations to avoid starvation, and this was still the situation when Hrdlika and Russell arrived in the early 1900s.

Both Hrdlika and Russell struggled with the dilemma of poverty coincident with obesity. Russell knew that the life of these Indians was arduous; sedentary behavior could not be a cause of obesity in the Pima. Instead, he proposed that a dietary factor was responsible. “Certain articles of their diet appear to be markedly flesh producing,” Russell wrote. Hrdlika suggested that “the role played by food in the production of obesity among the Indians is apparently indirect.” He suggested that life on the reservation might be relatively sedentary and this could play a role—“the change from their past active life to the present state of not a little indolence”—but he did not appear particularly confident about it. After all, he wrote, obesity was quite rare among the Pueblo, “who have been of sedentary habits since ancient times.” And obesity among the Pima was found “largely but not exclusively” in the women, and the women of the tribe worked considerably harder than the men, spending their days harvesting the crops, grinding corn, wheat, and mesquite beans and carrying whatever burdens were not carried by pack animals.

Hrdlika also noted that by 1905 the Pima diet already included “everything obtainable that enters into the dietary of the white man,” which raises the possibility that this might have been responsible for the obesity. At the half-dozen trading posts that opened on the Pima reservation after 1850, the