You can drive down the road in many communities and pass five or six service stations, fast food restaurants, and convenience stores in less than a mile. One Exxon station near my home has not only a food market with the usual chips and snack foods, but also a Dunkin' Donuts franchise inside it. And a Texaco station off the interstate had a food market, Dunkin' Donuts, and Subway. Fast food is infiltrating our culture. There are fast food restaurants inside some schools.
Malls have food courts.
Fast foods are showing up on airline flights and in airports. It's basically everywhere. And schools that don't house fast food chains serve hamburgers, pizza, tacos, or other fast foods anyway. You can argue that we're biologically programmed to eat such food because it's high in fat and sugar. Laboratory rats will eat that kind of food if you give them access to it, and they can become quite obese.