At the same time, the researchers emphasized that "the growth in these restaurants, and especially fast-food restaurants, is to a large extent a response to the increasing scarcity and increasing value of household or nonmarket time." In other words, economic changes such as greater participation in the labor market by women have increased the demand for fast, convenient meals.

 As the NBER's summary of the paper put it, "fast-food or convenience meals should rightly be considered as much an effect as a cause of American eating patterns." Spurlock seems to grasp this point. "Why do we go to fast-food restaurants?" he said at the D.C. film festival. "Because it's easy."

 Although he conceded that fast-food chains respond to consumer demand, Spurlock criticized them for failing to provide conspicuous nutritional information. He praised TGI Friday's for deciding to include calorie counts on its menus and suggested McDonald's could do the same, but "they fear losing money."

 Even if that's true, it's not the end of the story. Presumably TGI Friday's decided it could make money by changing its menus, attracting business from competitors who are less forthcoming. The market will determine who is right.

 Even while urging his audience to demand healthier options, Spurlock warned that fast-food chains "owe their loyalty to stockholders, not to you." If he had taken Ray Kroc's observation to heart, he would have realized that stockholders get what they want only when customers do.