The Omnivore's Dilemma: A Natural History of Four Meals

by Michael Pollan

To eat corn directly (as Mexicans and many Africans do) is to consume all the energy in that corn, but when you feed that corn to a steer or a chicken, 90 percent of its energy is lost—to bones or feathers or fur, to living and metabolizing as a steer or chicken. This is why vegetarians advocate eating “low on the food chain” every step up the chain reduces the amount of food energy by a factor of ten, which is why in any ecosystem there are only a fraction as many predators as there are prey. But processing food also burns energy. What this means is that the amount of food energy lost in the making of something like a Chicken McNugget could feed a great many more children than just mine, and that behind the 4,510 calories the three of us had for lunch stand tens of thousand of corn calories that could have fed a great many hungry people.