Hockenbury Discovering Psychology 5th txtbk

Biological Motivation323For example, think about what you ateyesterday. Now contrast your choices withfood preferences in other cultures. A typicaldiet for the Dusan of northern Borneoin Southeast Asia includes anteater, gibbon(a small ape), snake, mouse, and ratmeat. After these meats have spoiled to thepoint of being liquefied, the Dusan consumethem with rice. South American Indianseat head lice, bees, iguanas, andmonkeys. The Guianese of South Americaeat pebbles as a regular part of their diet,while the Vedda of Sri Lanka like rotted wood (see Fieldhouse, 1986). Clearly,cultural experience shapes our food choices (Rozin, 2006, 2007).Themes of food and eating permeate many different dimensions of our lives. Psychologically,eating can be related to emotional states, such as depression, anxiety,or stress (Macht, 2008). Interpersonally, eating is often used to foster relationships,as when you have friends over for dinner or take a potential customer to lunch. Weoften rely on food-related adjectives to describe other people, as when we say thatsomeone has a sweet disposition or a sour outlook on life. And, interestingly, our judgmentsabout others may be influenced by what they eat (Vartanian & others, 2007).In the next several sections, we look at what researchers have learned about themotivational factors that trigger hunger and eating behavior. As you’ll see, theseresearch efforts have focused on answering several key questions:• What signals regulate the motivation to start and stop eating?• How do people maintain a stable body weight over time?• Why do people become overweight or obese?• What causes eating disorders?Delicious or Disgusting? Theneed to eat is a universal humanmotive. However, cultureinfluences what we eat, whenwe eat, and how we eat (Rozin,1996, 2007). At a Cambodianmarketplace, this young boy iscarrying a platter of cooked spiders,a local delicacy. While nota feature at your typical U.S.restaurant, insects are standardfare in many countries. For example,grasshoppers, ant and flylarvae, and worms can be purchasedas snacks in traditional markets inMexico, where they have been a staple ofthe diet for thousands of years.Energy HomeostasisCalories Consumed Calories ExpendedIn order to explain the regulation of hunger and eating behavior, we need to beginwith some basics on how food is converted to energy in the body. The food thatyou eat is broken down by enzymes and gradually absorbed in your intestines. Aspart of this process, food is converted into amino acids, fatty acids, and simple sugars,providing “fuel” for your body. The simple sugar glucose, commonly calledblood sugar, provides the main source of energy for all mammals, including humans.In the liver, glucose is converted to and stored as glycogen, which can be easilyconverted back to glucose for energy. The hormone insulin, secreted by the pancreas,helps control blood levels of glucose and promotes the uptake of glucose bythe muscles and other body tissues. Insulin also helps in regulating eating behaviorand maintaining a stable body weight.About one-third of your body’s energy is expended for the routine physicalactivities of daily life, such as walking, lifting objects, brushing your teeth, and digestingthe food you eat. The remaining two-thirds of your body’s energy is usedfor continuous bodily functions that are essential to life, such as generating bodyheat, heartbeat, respiration, and brain activity. When you are lying down and resting,the rate at which your body uses energy for vital body functions is referred toas your basal metabolic rate (BMR).Obviously, you have to eat in order to have sufficient immediate energy for vitalbody functions and to survive. But another reason you eat is to maintain a reserveof stored energy. Adipose tissue, or body fat, is the main source of stored calories.Your liver, which monitors glucose levels in your bloodstream, can utilize this storedenergy if necessary.Not one man in a billion, when takinghis dinner, ever thinks of utility. Heeats because the food tastes good andmakes him want more.—WILLIAM JAMES Principlesof Psychology (1890)glucoseSimple sugar that provides energy and isprimarily produced by the conversion ofcarbohydrates and fats; commonly calledblood sugar.insulinHormone produced by the pancreas thatregulates blood levels of glucose and signalsthe hypothalamus, regulating hunger andeating behavior.basal metabolic rate (BMR)When the body is at rest, the rate at whichit uses energy for vital functions, such asheartbeat and respiration.adipose tissueBody fat that is the main source of stored,or reserve, energy.