Encyclopedia of Diets - A Guide to Health and Nutrition

eats voraciously far more than she needs to satisfy her

hunger, feels guilty about eating, and then exercise or

purges to get rid of the unwanted calories. At first this

may happen only occasionally, but gradually these

sessions of bingeing and purging become routine and

start to intrude on the person’s friendships, daily activ-

ities, and health. Eventually these practices have seri-

ous physical and emotional consequences that need to

be addressed by healthcare professionals.

Demographics

Bulimia nervosa is primarily a disorder of indus-

trialized countries where food is abundant and the

culture values a thin appearance. Internationally, the

rate of bulimia has been increasing since the 1950s.

Bulimia is the most common eating disorder in the

United States. Overall, about 3% of Americans are

bulimic. Of these 85–90% are female. The rate is high-

est among adolescents and college women, averaging

5–6%. In men, the disorder is more often diagnosed in

homosexuals than in heterosexuals. Some experts

believe that number of diagnosed bulimics represents

only the most severe cases and that many more people

have bulimic tendencies, but are successful in hiding

their symptoms. In one study, 40% of college women

reported isolated incidents of bingeing and purging.

Bulimia affects people from all racial, ethnic, and

socioeconomic groups. The disorder usually begins

later in life than anorexia nervosa. Most people begin

bingeing and purging in their late teens through their

twenties. Men tend to start at an older age than

women. About 5% of people with bulimia begin the

behavior after age 25. Bulimia is uncommon in chil-

dren under age 14.

Competitive athletes have an increased risk of

developing bulimia nervosa, especially in sports

where weight it tied to performance and where a low

percentage of body fat is highly desirable. Jockeys,

wrestlers, bodybuilders, figure skaters, cross-country

runners, and gymnasts have higher than average rates

of bulimia. People such as actors, models, cheer-

leaders, and dancers who are judged mainly on their

appearance are also at high risk of developing the

disorder. This same group of people is also at higher

risk for developing anorexia nervosa. Some people are

primarily anorexic and severely restrict their calorie

intake while also purging the small amounts they do

eat. Others move back and forth between anorectic

and bulimic behaviors.

Causes and symptoms

Bulimia nervosa is a complex disorder that does

not have a single cause. Research suggests that some

people have a predisposition toward bulimia and that

something then triggers the behavior, which then

becomes self-reinforcing. Hereditary, biological, psy-

chological and social factors all appear to play a role.

Causes

Heredity. Twin studies suggest that there is an inher-

ited component to bulimia nervosa, but that it is

small. Having a close relative, usually a mother or a

sister, with bulimia slightly increases the likelihood

of other (usually female) family members developing

the disorder. However, when compared other inher-

ited diseases or even to anorexia nervosa, the genetic

contribution to developing this disorder appears less

important than many other factors. Family history

of depression, alcoholism, and obesity also increase

the risk of developing bulimia.

Biological factors. There is some evidence that buli-

mia is linked low levels of serotonin in the brain.

Serotonin is a neurotransmitter. One of its functions

is to help regulate the feeling of fullness or satiety

that tells a person to stop eating. Neurotransmitters

are also involved in other mental disorders such as

depression that often occur with bulimia. Other

research suggests that people with bulimia may

have abnormal levels of leptin, a protein that helps

regulate weight by telling the body to take in less

food. Research in this area is relatively new, and

the findings are still unclear.

KEY TERMS

Diuretic—A substance that removes water from the

body by increasing urine production.

Electrolyte—Ions in the body that participate in

metabolic reactions. The major human electrolytes

are sodium (Naþ), potassium (Kþ), calcium (Ca

2 þ), magnesium (Mg2þ), chloride (Cl), phos-

phate (HPO 42 ), bicarbonate (HCO 3 ), and sul-

fate (SO 42 ).

Neurotransmitter—One of a group of chemicals

secreted by a nerve cell (neuron) to carry a chem-

ical message to another nerve cell, often as a way of

transmitting a nerve impulse. Examples of neuro-

transmitters include acetylcholine, dopamine,

serotonin, and norepinephrine.

Obsessive-compulsive disorder—A psychiatric

disorder in which a person is unable to control the

desire to repeat the same action over and over.

Bulimia nervosa