I am a glutton. Most Americans are, it seems: more than two thirds of the population is overweight or obese, and that proportion continues to rise, even as public awareness of the importance of healthy eating is at an all-time high. I know what a healthy diet looks like, and I certainly don't enjoy being fat, so why is eating less such a difficult process? It turns out that every decision we make about eating is influenced by mental and physiological forces that are often outside of our awareness and control.