Consider, for example, the amount of water in your body. It may feel like it’s under your conscious control and indeed you can choose to have or delay a drink, but over the course of your life the amount of water in your body, and thus the concentration of the hundreds of thousands of dissolved chemicals that make you up, is precisely controlled internally, even as you drink, sweat and pee. The conscious control of fluid balance is temporary at best and largely an illusion. And the case of breathing is more obvious still if you try to stop doing it. Food intake is under little more conscious control than breathing or drinking, and this is why it is nearly as hard to limit food intake as it is to limit water or oxygen intake. What, when and how we eat is determined by complex systems that operate far below our conscious level.