Ian Cheney and Curt Ellis are college friends who discover, through a hair analysis, that the carbon in their bodies traces back mostly to corn. To find out how, they move to Greene, Iowa, the town where both their great-grandfathers once farmed, and rent one acre of land to grow it themselves. With help from local farmers, genetically modified seed, and government subsidies, they produce a bumper crop, then try to follow it into the food system. The corn does not go to a dinner table. It becomes high fructose corn syrup and feed for cattle penned in a feedlot, fattened faster than their bodies were built to handle. Along the way they talk with the farmers actually growing the crop, who explain why they keep planting corn even when the market price falls below what it costs to grow, thanks to the subsidy checks that make up the difference. The film uses one acre and two amateur farmers to explain why corn, more than any other ingredient, ended up inside almost everything Americans eat.