Population-wide assessments of physical activity are also difficult to make in any meaningful way. Those research agencies that traditionally study such things—the CDC’s Behavioral Risk Factor Surveillance 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 called 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 football 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 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.”