What's become clear is that one-third of the world's greenhouse gas emissions are food-related. And study after study shows that some food products—meat and dairy products from ruminant animals (primarily cattle and lamb), highly processed foods derived from industrially grown grains, and air-freighted specialty foods—use a far greater percentage of resources than plant-based foods and whole grains, regardless of where those plant-based foods come from or who produces them. Another way of putting this is that the calories of energy expended to produce meat, processed foods, and specialty foods far outweigh the caloric energy those foods provide. (And they use a heck of a lot more water, too.) It's the very definition of "unsustainable." The American diet is dependent on this greenhouse gas-intensive food, and we waste (by eating too much or simply tossing) more than 25 percent of it.