The fast-food industry certainly makes it easy for people to gain weight if they are regular consumers, but ultimately the choice is theirs. The industry is successful because they make food cheap (unlike many of the healthier alternatives);they make it accessible (through drive-thrus as well as overwhelming franchise presence); they enhance the flavorings in order to increase customer satisfaction level; they often prepare foods in a fat-saturated (but well disguised) manner; and they promote consistent visits to their establishments (through special sales or cross-promotions with movies or whatever else is popular and trendy).
The film offers some very powerful arguments to suggest that fast food and obesity are closely linked. The statistics showing that large numbers of people consume fast food on a regular basis, when considered alongside the amount of weight gained by Spurlock in his month-long experiment, cannot be ignored. Spurlock also makes the point that car culture and the ease of "drive-through" food makes it likely that many fast food consumers don't get sufficient exercise. He recreates this condition by taking cabs to the McDonald's locations in New York City. The use of artificial flavorings that enhance the eating experience make the food tempting, despite its lack of nutritive value. Finally, the title refers to the enormous portions and the economic lure of larger portions for low prices as a way to tempt consumers to eat more of the food than is healthy.