No animal can live without food. Let us then pursue the corollary of this: namely, food is about the most important influence in determining the organization of the brain and the behavior that the brain organization dictates.
J. Z. Young (1968) 1
Many of you reading this book are, I'm certain, interested in weight control (most likely your own). In order to modify one's weight, it's extremely helpful to understand the basic factors responsible for the starting and stopping of eating. In other words, you need to understand the basic factors responsible for hunger and satiety. This information will help you understand what might be wrong if someone is eating too much or too little, and will also give you ideas about how to change the amount that someone eats. Perhaps most interestingly, this information will tell you what will not affect the amount that someone eats. This chapter will explain why filling up with water won't decrease how many calories you eat, something that anyone familiar with the basic laboratory research on eating knows.
Given that the focus of this chapter is on hunger and satiety, its material is more closely related to physiology than that of most of the other chapters. However, particularly toward the end of this chapter, I'll also discuss the relationships of hunger and satiety to aspects of our surroundings. Think of this chapter as providing you with the psychophysiological framework in which to place much of the social and cultural information on eating that you'll read about in later chapters.
The story of the scientific investigation of hunger and satiety reads like a minihistory of psychology laboratory technique. For each time period, the