Farmers grow plants to feed animals. Animals eat a lot. Cows eat more than we do. To create "meat," we first have to grow plants.

When energy is converted from plants to meat, most of it is lost. When you eat a cow you don't get the energy of all that cow's meals combined. You get a tiny fraction of it. The cow burned off most of that energy by being alive and moving around.

If we grow human food instead, we can be roughly 16x more efficient. Less energy is lost from plants because plants get their energy directly from the sun.