Here are a few of the things that can make you hungry: seeing, smelling, reading, or even thinking about food. Hearing music that reminds you of a good meal. Walking by a place where you once ate something good. Even after you’ve just had a hearty lunch, imagining something delicious can make you salivate. Being genuinely hungry, on the other hand—in the sense of physiologically needing food—matters little. It’s enough to walk by a doughnut shop to start wanting a doughnut. Studies show that rats that have eaten a lot are just as eager to eat chocolate cereal as hungry rats are to eat laboratory chow. Humans don’t seem all that different. More often than not, we eat because we want to eat—not because we need to. Recent studies show that our physical level of hunger, in fact, does not correlate strongly with how much hunger we say that we feel or how much food we go on to consume.
That’s something of a departure from commonly held views of what it means to be hungry. Traditionally, hunger has been seen as largely physiological: our body becomes depleted and, to maintain homeostasis—the body’s status quo—certain hormones are released into our bloodstream and stomach to signal to our brain that it’s time to replenish its resources. We eat. We digest. We use up our store of energy. The process repeats. “There are literally thousands of studies on the behavioral and biological effects of prolonged food deprivation,” Michael Lowe, a psychologist at Drexel University who has been researching hunger since the late seventies, told me.
Food deprivation, however, is generally not a problem in modern, developed societies. While our ancestors had to struggle to consume enough calories, we can just go to the fridge or the supermarket. As a result, though newborns behave much like animals and our calorie-deprived ancestors—they eat when they are physiologically hungry (and they let you know when they feel that way)—that internal reliance soon goes away. From an early age, we learn to depend increasingly on external, socially, and culturally based cues. Infants as young as twelve months already show signs of taking eating cues from adults—and the eating behaviors that we learn at home often follow us later in life. Lowe calls it the difference between homeostatic and hedonic eating: eating for need and eating for pleasure.
For the rest of the story: http://www.newyorker.com/online/blogs/mariakonnikova/2014/04/why-we-eat-and-why-we-gain-weight.html?utm_source=www&utm_medium=tw&utm_campaign=20140410