One third of the world's grain is fed to livestock, but animal foods account for only one tenth of the world's caloric intake. In the USA, about two thirds of the harvested acreage is used to grow food for livestock. Western developed nations export 3 million tonnes of grain protein to underdeveloped nations and import 4 million tonnes of protein in oilseeds and fish from these countries, most of which is fed to livestock. One third of Africa's protein-rich peanuts are fed to European livestock.
To feed the entire world on an average American diet would require twice the world's existing arable land and 80% of the world's energy.