Good Calories, Bad Calories (43 page)

For the past decade, public-health authorities have tried to explain the obesity epidemic in the United States and elsewhere. In 1960, government researchers began surveying Americans about their health and nutrition status. The first of these surveys was known as the National Health Examination Survey. It was fol owed by an ongoing series of National Health and Nutrition Examination Surveys (NHANES), of which there have been four so far.

According to these surveys, through the 1960s and early 1970s, 12–14 percent of Americans were obese. This figure rose by 8 percent in the 1980s and early 1990s, and another 10 percent by the turn of this century.

This doubling of the proportion of obese Americans is consistent through al segments of American society, although obesity remains more common among African Americans and Hispanics than among whites and other ethnic groups, and most common among those in the lowest income brackets and poorly educated. Children were not exempt from this trend. The prevalence of overweight in children six to eleven years old more than doubled between 1980 and 2000; it tripled in children aged eleven to nineteen.*65

Some factor of diet and/or lifestyle must be driving weight upward, because human biology and our underlying genetic code cannot change in such a short time. The standard explanation is that in the 1970s we began consuming more calories than we expended and so as a society we began getting fatter, and this tendency has been particularly exacerbated since the early 1980s.

Authorities phrase this concept differently, but the idea is invariably the same. The psychologist Kel y Brownel , director of the Yale Center for Eating and Weight Disorders, coined the term “toxic environment” to describe an American culture “that encourages overeating and physical inactivity” and so encourages obesity as a consequence. “Cheeseburgers and french fries, drive-in windows and supersizes, soft drinks and candy, potato chips and cheese curls, once unusual, are as much our background as trees, grass, and clouds,” says Brownel . “Few children walk or bike to school; there is little physical education; computers, video games, and televisions keep children inside and inactive; and parents are reluctant to let children roam free to play.”

In an editorial entitled “The Ironic Politics of Obesity” published by Science in 2003, the New York University nutritionist Marion Nestle summed up this hypothesis of obesity and the obesity epidemic in two words: “improved prosperity.” Nestle, like Brownel , considered the food and entertainment industries culpable: “They turn people with expendable income into consumers of aggressively marketed foods that are high in energy but low in nutritional value, and of cars, television sets, and computers that promote sedentary behavior. Gaining weight is good for business,” Nestle wrote.

SOURCE: Centers for Disease Control and Prevention, National Center for Health Statistics, Health, United States, 2005, figure 15.

Obesity rates in America, according to the Centers for Disease Control, with the upturn of the obesity epidemic apparently beginning in the 1970s or early 1980s.

More than one bil ion adults worldwide are overweight, according to the World Health Organization; three hundred mil ion are obese and obesity rates have “risen three-fold or more since 1980 in some areas of North America, the United Kingdom, Eastern Europe, the Middle East, the Pacific Islands, Australasia and China.” In these regions, too, prosperity is seen as the problem. “As incomes rise and populations become more urban,” the WHO said,

“diets high in complex carbohydrates give way to more varied diets with a higher proportion of fats, saturated fats and sugars. At the same time, large shifts towards less physical y demanding work have been observed worldwide. Moves towards less physical activity are also found in the increasing use of automated transport, technology in the home, and more passive leisure pursuits.”

It al sounds reasonable, but there are so many other variables, so many other possibilities—including the fact that the consumption of refined carbohydrates and sugars has also been increasing dramatical y. To determine which hypothesis is most likely to be correct, it’s useful to focus on the United States, because it offers a starting point for the epidemic—between the late 1970s and mid-1980s*66 —and resonably consistent data with which to work.

The question of how much we eat, whether in a population or as an individual, is difficult to assess, but the evidence suggests that we consumed more calories on average in the 1990s than we did in the 1970s. According to NHANES, American men increased their calorie consumption from 1971 to 2000 by an average of 150 calories per day, while women increased their consumption by over 350 calories. This increase in energy intake, according to a 2004 report published by the Centers for Disease Control, was “attributable primarily to an increase in carbohydrate intake.” Though the percentage of fat in the diet decreased for both sexes, the absolute amount of dietary fat decreased only for men. On average, women ate fifty calories more fat each day in 2000 than they did in 1971, and men ate fifty calories less. The NHANES data suggest that either calories or carbohydrates could account for the increase in weight in the United States during this time; it would be difficult to implicate dietary fat.

The identical conclusion could be drawn from the evidence gathered by the U.S. Department of Agriculture and published in a report entitled Nutrient Content of the U.S. Food Supply, 1909–1997. The USDA says that the American food supply offered up thirty-three hundred calories a day per capita between 1971 and 1982. By 1993, it had climbed to thirty-eight hundred calories, and it remained at that level through 1997. This increased availability, and so perhaps consumption, of five hundred calories each day could conceivably explain the obesity epidemic. But carbohydrate consumption also turned upward after 1982. Of the five hundred additional calories available for consumption each day, 90 percent came from carbohydrates. The remaining 10 percent were from protein and fat, in descending order. Saturated fat dropped from fifty-three grams a day in 1971 to fifty in 1997.*67

The change in calories consumed between 1971 and 2000 in women ages 20–74 years (upper chart) and in men ages 20–74 (lower chart), according to the National Health and Nutrition Examination Surveys.

In 1997, the University of Alabama nutritionist Roland Weinsier reviewed this evidence in an article entitled “Divergent Trends in Obesity and Fat Intake Patterns: The American Paradox.” “It appears that efforts to promote the use of low-calorie and low-fat food products have been highly successful,”

Weinsier noted, but the reduction in fat intake did “not appear to have prevented the progression of obesity in the population.”

Population-wide assessments of physical activity are also difficult to make in any meaningful way. Those research agencies that traditional y study such things—the CDC’s Behavioral Risk Factor Surveil ance System, in particular—have no evidence that would shed light on physical activity during the decade in which the obesity epidemic began. They do have evidence suggesting that Americans were no less active at the end of the 1990s than they were at the beginning of that decade, despite the continued rise in weight and obesity throughout this period. We know, too, that the obesity epidemic coincided with what might be cal ed an exercise or sports epidemic in America, accompanied by the explosion of an entire industry dedicated to leisure-time pursuits. It’s worth remembering that in the 1960s Jack La Lanne was the nation’s only physical-fitness guru, Gatorade existed solely for the use of University of Florida footbal players, and skateboarding, in-line skating, snowboarding, mountain 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 mil ion a year; in 2005, revenues were $16 bil ion, and nearly forty mil ion 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 mil ion 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 col eagues 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 physical y demanding occupations, that poverty is a risk factor for obesity is another compel ing reason to question the notion that sedentary behavior is a cause.