It’s midnight; you are struggling to get through the final pages of your psychology chapter. Suddenly, your stomach lets out a desperate gurgling cry. “Feed me!” Time to heat up that frozen burrito, you say to yourself as you head into the kitchen. But wait! Are you really hungry?

LO 7 Discuss how the stomach and the hypothalamus make us feel hunger.

THE STOMACH AND HUNGER In a classic study, Walter Cannon and A. L. Washburn (1912) sought to answer this question (well, not this exact question, but they did want to learn what causes stomach contractions). Here’s a brief synopsis of the experiment: To help monitor and record his stomach contractions, Washburn swallowed a balloon that the researchers could inflate. The researchers also kept track of Washburn’s hunger levels, having him push a button anytime he felt “hunger pangs” (Figure 9.2). What did the experiment reveal? Anytime he felt hunger, his stomach contracted.

BLOOD CHEMISTRY AND HUNGER Cannon and Washburn’s experiment demonstrates that the stomach plays an important role in hunger, but it’s just one piece of the puzzle. One reason we know this is that cancer patients who have had their stomachs surgically removed do not differ from people with their stomachs intact in regard to feelings of satiety (that is, feeling full) or the amount of food eaten during a meal (Bergh, Sjöstedt, Hellers, Zandian, & Södersten, 2003). We also must consider the chemicals in the blood, such as glucose, or blood sugar. When glucose levels dip, the stomach and liver send signals to the brain that something must be done about this reduced energy situation. The brain, in turn, will initiate a sense of hunger.

THE HYPOTHALAMUS AND HUNGER One part of the brain that helps regulate hungry feelings is the hypothalamus, which can be divided into functionally distinct areas. When the lateral hypothalamus is activated, appetite increases. This occurs even in well-fed animals if this region is stimulated electrically. Destroy this area of the brain, and animals lose interest in food, even to the point of starvation. The lateral hypothalamus is also involved in motivating behavior, ultimately helping to preserve the balance between energy supply and demand (Leinninger, 2011).

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If the ventromedial hypothalamus becomes activated, appetite declines, causing an animal to stop eating. Disable this region of the brain, and the animal will overeat to the point of obesity. The ventromedial hypothalamus receives information about levels of blood glucose and other feeding-related stimuli, as it too works to maintain the body’s energy balance (King, 2006).

The hypothalamus has a variety of sensors that react to information about appetite and food intake. Once this input is processed, appropriate responses are communicated via hormones in the bloodstream (Infographic 9.2). One such hormone is leptin, a protein emitted by fat cells that plays a role in suppressing hunger. Another is insulin, a pancreatic hormone involved in controlling levels of glucose in the bloodstream. With input from these and other hormones, the brain can monitor energy levels and respond accordingly. This complex system enables us to know when we are hungry, full, or somewhere in between.

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Biology is not the only factor influencing eating habits. We must also consider the culture and social context in which we eat. In the United States, most of our social activities, holidays, and work events revolve around food. We may not even be hungry, but when presented with a spread of food, we find ourselves eating. All too often we eat too fast, rushing to our next event, class, or meeting, not taking the time to experience the sensation of taste. We tend to match our food intake to those around us, although we may not be aware of their influence (Herman, Roth, & Polivy, 2003; Howland, Hunger, & Mann, 2012). Gender plays a role in eating habits as well. Using naturalistic observation, researchers found that women choose lower-calorie meals when eating with a man than when eating with another woman (Young, Mizzau, Mai, Sirisegaram, & Wilson, 2009).

PORTION DISTORTION A variety of factors drive our decisions to begin or stop eating, including hunger, satiety, and food taste (Vartanian, Herman, & Wansink, 2008). But more subtle variables, such as portion size, come into play too. In one study, participants at a movie theater were given free popcorn, some in medium-sized buckets and others in large buckets. Some of the buckets contained popcorn that was fresh, and others were filled with popcorn that was 14 days old. Participants given large buckets consistently ate 33% more than those given medium-size buckets, regardless of whether the popcorn was fresh or stale. The stale popcorn was described as “soggy” or “terrible,” yet the participants still ate more of it when given larger portions (Wansink & Kim, 2005). Remember this the next time you sit down in front of the TV with an entire bag of snack food.

Portion size is just one factor influencing food intake. Visual cues are also important, especially when they provide feedback about how much you have eaten. To study this, researchers gave college students tubes of potato chips to eat while watching a movie. In some of the tubes, every 7th chip was dyed red. Participants given tubes with the occasional red chips consumed 50% less than those given tubes with no red chips. Thus we see, interrupting mindless eating (Wait a second, that’s a red chip) can decrease the amount of food consumed in one sitting (Geier, Wansink, & Rozin, 2012).

In today’s world, a growing number of people are struggling with obesity, fueling popular interest in strategies for cutting down food intake. Two-thirds of adults in the United States are overweight, and one-third meet the criteria for obesity, defined as having a body mass index (BMI) of 30 or higher (Flegal, Carroll, Ogden, & Curtin, 2010; Ogden, Carroll, Kit, & Flegal, 2014). Adults aren’t the only ones battling the bulge; one-third of America’s children and teens are overweight (American Heart Association, 2014).

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SET POINT, SETTLING POINT, AND HEREDITY Surprisingly, there is relatively little fluctuation in adult weight over time. The communication between the brain and the appetite hormones help regulate the body’s set point, or stable weight that we tend to maintain despite variability in day-to-day exercise and intake of food. If you don’t consume enough calories and your weight falls below this set point, metabolism decreases, causing you to gain weight and return to your set point. Exceed the set point, and metabolism increases, once again moving you back toward your stable weight (Keesey & Hirvonen, 1997). The set point acts like a thermostat, helping to maintain a consistent weight in part through changes in metabolism.

Some critics of the set point model suggest that it fails to appreciate the importance of social and environmental influences (Stroebe, van Koningsbruggen, Papies, & Aarts, 2013). These theorists suggest we should consider a settling point, which is less rigid and can explain how the “set” point can actually change based on the relative amounts of food consumed and energy used. A settling point can help us understand how body weight may shift to a newly maintained weight, and why so many people are overweight as a result of environmental factors, such as bigger meal portions, calorie-dense foods, increased dining at restaurants, and eating while engaged in another activity like watching television. Nevertheless, there does seem to be a genetic component of body weight. Studies suggest that the heritability of BMI is around 65% (Speakman et al., 2011). More research is needed, but it seems we may be genetically predisposed to stay within a certain weight range.

OVEREATING, SLEEP, AND SCREEN TIME As you well know, deciding what and when to eat does not always come down to being hungry or full. We must consider how motivation plays a role in our eating patterns. Some people eat not because they are hungry, but because they are bored, sad, or anxious. Others eat simply because the clock indicates that it is mealtime. Higher brain regions involved in eating decisions can override the hypothalamus, driving you to devour that cheesy burrito even when you don’t need the calories.

If our set point helps us maintain a certain weight, how does this impact people who struggle with obesity? Obesity is both a physiological and psychological issue. There is some evidence that genes play a role, and we also know some illnesses can lead to obesity (Anis et al., 2010; Plomin et al., 2013). But one often overlooked lifestyle factor related to obesity is sleep. Preliminary research suggests that inadequate sleep is linked to weight problems (a negative correlation between sleep and weight gain). In contrast, individuals who sleep between 6 and 8 hours are more likely to lose weight. Additionally, a positive correlation exists between screen time and weight gain: the more screen time, the more weight gain. When screen time interferes with making healthy eating choices and getting regular physical exercise, weight loss is not as successful (Elder et al., 2012).

To lose weight, one must eat less and move more (Table 9.2); in other words, use more calories than you are taking in. Our ancestors didn’t have to worry about this. They had to choose foods rich in calories to give them energy to sustain themselves. Although this was a very efficient means of survival for them, it doesn’t work out so well for us. When experiencing a “famine” (decrease in the caloric intake our bodies are accustomed to), our metabolism naturally slows down, requiring fewer calories and making it harder to lose weight.

In response to the obesity problem in the United States, policies have been implemented to raise awareness and discourage overeating. One such intervention is requiring information about calories to be clearly labeled, which can serve as a visual cue or reminder. Providing this information can impact healthy food choices. However, accessibility to comparably priced healthy alternatives must be increased (in vending machines, for example)—but this too may require changes in policy (Stroebe et al., 2013).

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LO 8 Outline the characteristics of the major eating disorders.

Although many people deal with obesity, others struggle with food in a different way. Eating disorders are serious dysfunctions in eating behavior that can involve restricting food consumption, obsessing over weight or body shape, eating too much, and purging (American Psychiatric Association, 2013). Eating disorders usually begin in the early teens and typically affect girls. That doesn’t mean boys do not struggle with eating disorders; 1 in 4 children ages 5–13 with an eating disorder is male (Madden, Morris, Zurynski, Kohn, & Elliot, 2009). However, the causes of body image distortions often differ according to gender. Females desire to be smaller and thinner, whereas males seek an “idealized masculine shape” (Darcy et al., 2012). Let’s take a look at three of the most recognized eating disorders.

ANOREXIA NERVOSA One of the most commonly known eating disorders is anorexia nervosa, which is characterized by self-imposed restrictions on calories needed to maintain a healthy weight. These restrictions lead to extremely low body weight in relation to age, sex, development, and physical health. Someone with this disorder has an extreme fear of gaining weight and getting fat, even though her body weight is extremely low. Often there is an altered and distorted sense of body weight and figure, and no realization of the “seriousness” of her low body weight (American Psychiatric Association, 2013). In some cases, women experience an absence of menstrual periods, a condition called amenorrhea (Attia & Roberto, 2009). Other severe symptoms may include brain damage, multiorgan failure, infertility, and thinning of the bones (National Institute of Mental Health [NIMH], n.d.). Anorexia is associated with the highest death rates of all psychological disorders (Darcy et al., 2012; Harris & Barraclough, 1998; Smink, van Hoeken, & Hoek, 2012). Approximately 20% of those deaths are due to suicide (Smink et al., 2012). Although anorexia nervosa affects mostly women and adolescent girls, males can also be affected (particularly those involved in wrestling, running, or dancing, who are required to maintain a certain weight).

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BULIMIA NERVOSA Another eating disorder is bulimia nervosa, which involves recurrent episodes of binge eating, or consuming a large amount of food in a short period of time (with that amount being greater than most people would eat in the same time frame). While bingeing, the person feels a lack of control and thus engages in purging behaviors to prevent weight gain—for example, self-induced vomiting, misuse of laxatives, fasting, or excessive exercise (American Psychiatric Association, 2013). Like anorexia, bulimia more often affects women and girls (Stice, Marti, Shaw, & Jaconis, 2009). Bulimia also has serious health risks, such as high blood pressure, heart disease, and Type 2 diabetes (Haedt-Matt & Keel, 2011). Other symptoms include decaying teeth, damage to the throat, gastrointestinal disorders, and electrolyte imbalance from vomiting, which can lead to heart attack (NIMH, n.d.). Research has found that 23% of deaths associated with bulimia nervosa result from suicide (Smink et al., 2012).

BINGE-EATING DISORDER You may have also heard of binge-eating disorder (American Psychiatric Association, 2013), characterized by episodes of excessive food consumption (eating more than most people would eat in the same amount of time and in similar situations). As in bulimia, the individual feels unable to control her eating during that period of time, but the difference is that she does not engage in excessive weight control or purging behaviors. Some psychological effects could include feelings of embarrassment about how much food has been consumed, depression, and guilt after overeating.

We know that eating disorders are apparent in America—we see evidence of them on television, in magazines, and in everyday life. But are these disorders also observed in India, South Africa, Egypt, and other parts of the world?

across the WORLD

Question 1

1. stomach was contracting.

2. stomach was still.

3. blood sugar went up.

4. ventromedial hypothalamus was active.

Question 2

1. restrictions of energy intake.

2. extreme fear of gaining weight, although one’s body weight is extremely low.

3. a distorted sense of body weight and figure.

4. extreme overeating followed by purging.

Question 3