322 Chapter
10
Motivation and Emotion
Not everyone agrees with the set-point explanation for obesity. Pointing to the
rapid rise in obesity over the last several decades in the United States, some research-
ers suggest that the body does not try to maintain a fi xed weight set point. Instead,
they suggest,
the body has a settling point, determined by a combination of our
genetic heritage and the nature of the environment in which we live. If high-fat foods
are prevalent in our environment and we are genetically predisposed to obesity, we
settle into an equilibrium that maintains relatively high weight. In contrast, if our
environment
is nutritionally healthier, a genetic predisposition to obesity will not be
triggered, and we will settle into an equilibrium in which our weight is lower
(Comuzzie & Allison, 1998; Pi-Sunyer, 2003).
Eating Disorders
Eating disorders are among the 10 most frequent causes of disability in young
women. One devastating
weight-related disorder is anorexia nervosa. In this severe
eating disorder, people may refuse to eat while denying that their behavior and
appearance—which can become skeleton-like—are unusual. Some 10% of people
with anorexia literally starve themselves to death (Striegel-Moore & Bulik, 2007).
Anorexia nervosa mainly affl icts females between the ages of 12 and 40, although
both men and women of any age may develop it. People
with the disorder are often
successful, attractive, and relatively affl uent. The disorder often begins after serious
dieting, which somehow gets out of control. Life begins to revolve around food:
Although people with the disorder eat little, they may cook for others, go shopping
for
food frequently, or collect cookbooks (Polivy, Herman, & Boivin, 2005; Myers,
2007; Jacobs et al., 2009).
A related problem,
bulimia, from which Lisa Arndt (described earlier) suffered,
is a disorder in which people binge on large quantities of food. For instance, they
may consume an entire gallon of ice cream and a whole pie in a single sitting. After
such a binge, sufferers feel guilt and depression and often induce vomiting or take
laxatives to rid themselves of the food—behavior known as purging. Constant
binging-and-purging cycles and the use of drugs to
induce vomiting or diarrhea
can lead to heart failure. Often, though, the weight of a person with bulimia remains
normal (Mora-Giral et al., 2004; Couturier & Lock, 2006).
Eating disorders represent a growing problem: Estimates show that between 1%
and 4% of high school–age and college-age women have either anorexia nervosa or
bulimia. As many as 10% of women suffer from bulimia at some point in their lives.
Furthermore, an increasing number of men are diagnosed with eating disorders; an
estimated 10% to 13% of all cases occur in males (Kaminski et al., 2005; Swain, 2006;
Park, 2007).
What are the causes of anorexia nervosa and bulimia? Some researchers suspect
a biological cause such as a chemical imbalance in the hypothalamus or pituitary
gland, perhaps brought on by genetic factors. Furthermore,
brain scans of people
with eating disorders show that they process information about food differently from
healthy individuals (see Figure 3; Polivy & Herman, 2002; Santel et al., 2006; Klump
& Culbert, 2007).
Others believe that the cause has roots in society’s valuation of slenderness and
the parallel notion that obesity is undesirable. These researchers maintain that people
with anorexia nervosa and bulimia become preoccupied with their weight and take
to heart the cliché that one can never be too thin.
This may explain why eating
disorders increase as countries become more developed and Westernized and dieting
becomes more popular. Finally, some psychologists suggest that the disorders result
from overly demanding parents or other family problems (Grilo et al., 2003; Couturier
& Lock, 2006; Kluck, 2008).
The complete explanations for anorexia nervosa and bulimia remain elusive.
These disorders most likely stem from both biological and social causes, and
successful treatment probably encompasses several strategies,
including therapy and
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