Mayer also believed that this link between physical inactivity and overweight explained another troubling conflict in the evidence. How could the prevalence of obesity and overweight be increasing in the 1950s if calorie consumption, according to USDA estimates, had dropped significantly since the turn of the century? (Recall the changing-American-diet story.)

Descriptions of typical meals in the nineteenth century, as Mayer noted, suggest they were enormous compared with what we eat today. Breakfasts of the British gentry of the late nineteenth century “frequently assumed prodigious proportions,” according to the anthropologist Eric Ross. In a typical country house, wrote one British authority in the late 1880s, breakfasts consisted of “fish, poultry, or game, if in season; sausages, and one meat of some sort, such as mutton cutlets, or filets of beef; omelettes, and eggs served in a variety of ways; bread of both kinds, white and brown, and fancy bread of as many kinds as can conveniently be served; two or three kinds of jam, orange marmalade, and fruits when in season; and on the side table, cold meats such as ham, tongue, cold game, or game pie, galantines, and in winter a round of spiced beef.” In the United States, according to the historian Hillel Schwartz, such enormous meals were also the norm: “The 75-cent special at Fred Harvey restaurants in the late 1870s included tomato purée, stuffed whitefish with potatoes, a choice of mutton or beef or pork or turkey, chicken turnovers, shrimp salad, rice pudding and apple pie, cheese with crackers, and coffee…. When life insurance medical directors sat down to their banquet in 1895, they had clams, cream soup, kingfish with new potatoes, filet mignon with string beans, sweetbreads and green peas, squabs and asparagus, petits fours, cheese with coffee, and liqueurs to follow….” Incredibly, Schwartz noted, these gargantuan repasts “were two or more courses and thirty to sixty minutes shorter than formal dinners of the previous era, and their portions were smaller.”

Having concluded that caloric intake had actually fallen since the nineteenth century, Mayer pioneered the practice of implicating the sedentary nature of our lives as the “most important factor” in obesity and the chronic diseases that accompany it. Americans in the mid-twentieth century, as Mayer perceived it, were more inert than their “pioneer forebears,” who were “constantly engaged in hard physical labor.” Every modern convenience, from the car to the extensions on our telephones and even the electric toothbrush, only served to make our lives ever more sedentary. “The development of obesity (and of heart disease as well as a number of other pathologic conditions),” Mayer wrote in 1968, “is to a large extent the result of the lack of foresight of a civilization which spends tens of billions annually on cars, but is unwilling to include a swimming pool and tennis courts in the plans of every high school.”