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Disorders of Eating: Introduction
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Eating disorders are complex mental
health disorders with significant physiological effects and an associated
environmental overlay. They occur most commonly in adolescent girls
and young adult women; however, males are also affected. It was
previously thought that Caucasian girls of high socioeconomic status
were primarily affected, but in the United States, eating disorders
occur in all socioeconomic classes, races, and ethnicities.8 Eating
disorders are diagnosed using clinical criteria established by the
American Psychiatric Association, as listed in the Diagnostic
and Statistical Manual of Mental Disorders, 4th edition.9 The
disorders currently recognized are anorexia nervosa, bulimia nervosa,
and eating disorder not otherwise specified, which includes binge
eating disorder. Eating disorders fall on the extreme end of the
eating behavior spectrum, with healthy eating patterns at the other
end and disordered eating, or unhealthy dieting practices, falling
somewhere in the middle.
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Epidemiology,
Specific Populations at Risk, and Associated Disorders
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Anorexia nervosa (AN) is an eating disorder characterized by
food restriction that typically results in extreme weight loss.
As shown in Table 73-1, the diagnostic criteria
for AN include low weight, distorted perception of body shape and
size, intense fear of weight gain, and amenorrhea. While many of
the complications associated with AN are due to malnutrition (see Chapter 29), patients are often in denial
about the seriousness of their degree of weight loss. AN typically
affects adolescent girls, with an average prevalence of 0.5% to 3.7% in
young women.9 The diagnosis is most often made
in early to middle adolescence. Critical risk periods appear to
be developmental transition (eg, a transition to middle/junior high
school, high school, or college) and a decision to embark on diets.
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Bulimia nervosa (BN) is characterized by binge and
purge behavior and typically affects 1.1% to 4.2% of
adolescent/young adult women.9 The word bulimia means
a condition characterized by perpetual insatiable hunger with bouts
of overeating. Table 73-2 shows the diagnostic
criteria for BN. Binging episodes are followed by purging, a compensatory
behavior that may be vomiting, food restriction, use of laxatives,
or compulsive overexercising. Patients with BN report anxiety about
gaining weight. However, in contrast to anorexia nervosa, most individuals
with BN are normal in weight. Therefore, it is critical to obtain
a history of binging and purging behavior to establish the diagnosis.
The mean age of onset of BN is 18 years, with most diagnoses made
in middle to late adolescence and young adulthood. A history of
childhood sexual abuse is more common in patients with BN than in those
with AN.10
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Eating disorder not otherwise specified (EDNOS) is a diagnostic
category for patients who do not meet the full criteria for anorexia nervosa
or bulimia nervosa. For example, a patient who binges infrequently
or restricts food but does not have the associated weight loss or
amenorrhea may be diagnosed with a “partial eating disorder,” or
EDNOS (eTable 73.1).
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Binge eating disorder (BED) is the newest clinically recognized
eating disorder that is currently included under the diagnosis of
EDNOS. As shown in Table 73-3, BED is characterized
by binging behavior without compensation by purging. Therefore,
the majority of patients with BED are overweight. Among adolescents
who are actively seeking clinical care for weight management, up
to 35% meet the criteria for BED.11,12 Thus, while
it is likely that BED contributes to overweight, studies suggest
that overweight may precede the binge eating behavior.
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Pathophysiology
and Genetics
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The etiology of eating disorders is multifactorial, including
genetic, biological, psychological, and sociocultural influences.
Eating disorders are highly heritable, with higher rates of concurrence
among identical twins and/or first-degree relatives. Studies
of twins estimate a heritability of 30% to 50% for
anorexia nervosa.14 Although no specific genes
have been implicated, altered levels of several hormones (such as
leptin) and neuropeptides (such as serotonin) have been documented
in patients with eating disorders. Biological factors such as these
are likely to both contribute to the development of the eating disorder
and result from the associated behaviors, namely starvation and binging.
The psychological factors associated with anorexia nervosa include
perfectionism, anxiety, obsessive behavior, and low self-esteem.
bulimia nervosa is associated with psychological factors including
depression, anxiety, low self-esteem, personality disorders, disturbances
in social functioning (eg, inability to have meaningful interpersonal
relationships resulting in isolation from normal daily events), substance
abuse, and suicidal behavior. Sociocultural factors include the
thin ideal, valued in the United States since the early 20th century and
increasingly in developing nations today. Internalization of this
ideal, including the belief that thinness will bring happiness and
success, is associated with poor body image, dieting behavior, and
further preoccupation with thinness. Some organized efforts have
been made to address this problem. For example, at least 2 countries
have instituted body mass index (BMI) limits for participation in
runway modeling during fashion weeks. However, the established limit
of 18.0 kg/m2 still constitutes extreme
thinness and is defined as underweight by the World Health Organization.15 The Council
for Fashion Designers in America opted not to create body mass index
limits for models in the United States.
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Clinical Features
and Differential Diagnosis
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An eating disorder should be suspected any time an adolescent
loses significant weight, fails to gain appropriate weight, or develops food
avoidance. Symptoms and findings include hypothermia, fatigue, edema,
stunting of growth, delayed puberty, oligomenorrhea or amenorrhea,
lanugo and hair loss, brittle nails and hair, tooth decay and gingivitis,
Russell sign (calluses on the back of the hand from abrasions when
inducing vomiting), salivary gland enlargement, muscle cramps and
sometimes diarrhea from laxative abuse (see eTable 73.2).
Most of these physical findings and many of the initial alterations
in cognitive functioning are related to the degree of malnutrition, while
some result from purging behaviors. Since anorexia nervosa is often
characterized by weight loss, other diagnoses such as diabetes mellitus,
inflammatory bowel disease, celiac disease, hyperthyroidism, collagen
vascular disorders, malignancy, chronic infection such as tuberculosis
or human immunodeficiency virus, substance abuse and mental disorders
need to be considered (see eTable 73.3).
A diagnosis of BN requires consideration of additional medical conditions,
including a range of gastrointestinal illnesses (eg, gastroesophageal
reflux disease, gallbladder disease, ulcers).
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Diagnostic Evaluation
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The diagnosis of an eating disorder is based on the clinical
criteria established by the American Psychiatric Association and
outlined in Tables 73-1, 73-2, and 73-3.
Obtaining a complete history from the patient and family is critical
for establishing a diagnosis (Table 73-4).
Physical evaluation of a patient suspected of an eating disorder
includes measuring height and weight, calculating body mass index,
and plotting these variables on gender-specific curves.16 These
data points can be compared to prior growth history to assess changes.
If growth is normal, points should follow a curve that remains roughly
within the same percentiles. Lack of expected weight gain can be
an early warning sign of malnutrition, while lack of expected height
gain reflects long-term malnutrition. If no historical data are
available, the 50th percentile for age and gender can be used to
represent average growth. Obtaining vital signs,
including heart rate, blood pressure, and orthostatic changes, is
necessary to determine the severity of malnutrition. Laboratory
testing, including a pregnancy test, an erythrocyte sedimentation
rate, liver function tests, thyroid levels, and celiac screen, may
be needed to help clarify a diagnosis. In patients with restricting-type
anorexia, laboratory values are typically normal, while in patients
with purging, electrolyte changes such as significant hypokalemia can
be seen. Further evaluation may include an electrocardiogram, particularly
to look for arrhythmias and a prolonged QT interval.
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The complications of eating disorders affect multiple biological
systems, as shown in Table 73-5. For anorexia
nervosa, complications are related to the degree of malnutrition;
for bulimia nervosa, complications often arise from purging behavior.
One acute complication that emerges during treatment of a malnourished
patient is refeeding syndrome. Refeeding syndrome describes the
life-threatening electrolyte shifts that can occur when nutrition
is reintroduced (see Chapter 29). In response
to carbohydrate and protein feeding, insulin is released and facilitates the
transport of nutrients into cells for metabolism. Electrolytes are
drawn with the nutrients from the extracellular to the intracellular
space, causing a shift in fluids and electrolytes. Dramatic changes
in phosphorous, potassium, magnesium, and sodium can result is cardiac arrhythmias,
breakdown of muscle, edema, delirium, and death. Thus, severely
malnourished patients should be refed under close surveillance in a
hospital to monitor for signs of refeeding syndrome.
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The treatment for all eating disorder diagnoses is similar, since
those who suffer from anorexia nervosa, bulimia nervosa, and eating
disorder not otherwise specified share a preoccupation with food,
body weight, and body shape. Treatment for eating disorders typically
occurs in the outpatient setting. However, the Society for Adolescent
Medicine has developed indications for hospitalization for an adolescent
with an eating disorder, including severe malnutrition, electrolyte
disturbances, severe bradycardia or other cardiac dysrhythmias,
orthostatic changes, acute food refusal, and uncontrollable binging
and purging.17 Patients with anorexia nervosa are
most likely to meet these criteria. Patients who are failing outpatient
treatment may require a higher level of care, including intensive
outpatient or partial hospitalization programs or residential care
programs.
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Successful treatment typically requires a multidisciplinary team
knowledgeable in the care of patients with eating disorders. The team
should include (1) a physician who can monitor weight, vital signs,
and consequences of malnutrition; (2) a nutritionist who can assist
with meal planning and weight restoration; and (3) a therapist
who is knowledgeable about treating eating disorders.
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The initial medical goal is weight restoration for malnourished
patients, a critical first step to enable the patient to benefit
from psychological treatment. Long-term goals in the treatment of anorexia
nervosa include resumption of normal menstrual periods, healthy
eating habits and attitudes, and improved psychological functioning.
In treatment of bulimia nervosa, the critical first step is decreasing
the frequency of the binging and purging episodes. Medical monitoring
is important initially to make certain the patient’s electrolytes
are normalized, since purging-induced hypokalemia can lead to cardiac
arrhythmias and sudden death. Other important aspects of treatment
for bulimia include encouraging regular, moderate physical activity
and dental care, as recurrent self-induced vomiting may cause dental
erosions and caries.
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Nutritional treatment may involve a registered dietitian who
can develop a meal plan to provide optimal calories and guide healthy
eating habits, such as increased variety or decreased food phobias.
Patients should be encouraged to consume regular meals and snacks
throughout the day. In patients with binge or purge behaviors, meal
skipping should be discouraged, and certain foods might be avoided
because these may trigger subsequent binging or purging. Patients
with restricting behavior need help increasing variation in their diet.
Setting realistic weight goals may also be important. As patients
are improving their nutrition and restoring their weight, they often
require zinc supplementation and may benefit from a multivitamin
in addition to a calcium supplement with vitamin D.
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Psychological treatment aims to improve the patient’s
body image distortion, self-evaluation of weight or shape and intense
fear of becoming fat, and psychiatric comorbidities. Depression,
and anxiety and are the most common mental health disorders that
co-occur among patients with anorexia nervosa. The psychotherapeutic
treatment modality for adolescents with anorexia nervosa that has
demonstrated efficacy is family therapy.18 Further research
is necessary to determine the benefits of psychotropic medication,
including antidepressants and atypical neuroleptic medications.19,20 Antidepressant
medications, particularly selective serotonin reuptake inhibitors,
may be beneficial in treating coexisting symptoms of depression
or obsessive-compulsive disorder. Malnutrition itself may worsen
symptoms of anxiety, depression, and obsessive behavior. If symptoms
persist following weight restoration, medications may be more effective
in treating those symptoms.
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For adolescents and adults with bulimia nervosa, cognitive behavior
therapy and/or treatment with selective serotonin reuptake
inhibitors have demonstrated efficacy. In addition to depression
and substance abuse, patients struggling with bulimia nervosa frequently have
tremendous shame about their secretive behavior. Cognitive behavior
therapy targets thoughts, feelings, and behaviors in order to break
the binge/purge cycle and typically includes teaching patients
alternate coping skills for anxiety and depressive symptoms. Individuals
who have other mental health disorders may need other psychotropic
medications or psychotherapy. Chronic binging and purging may worsen
symptoms of anxiety, depression, and obsessive behavior. It is important
to reevaluate symptoms throughout the treatment and recovery process.
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Prognosis or Outcomes
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Generally, adolescents have better outcomes than adults, which
may be due to a shorter duration of illness among adolescents. Fifty
percent of adolescents are thought to have a good outcome; however,
recovery can take many years.21 For anorexia nervosa,
good prognostic indicators include early identification and entry
into treatment, short duration of symptoms, age less than 14 years,
anorexia nervosa restricting subtype rather than the binge/purge subtype,
and no other mental health disorder (such as depression, anxiety,
or substance abuse).22 For bulimia nervosa, studies
have shown a full recovery rate that is significantly higher than
for anorexia nervosa.23 However, the course of
recovery for all of the eating disorders can be long and marked
by relapse.22,24 The leading causes of death in
patients with anorexia nervosa are suicide and medical complications
resulting from malnutrition/starvation. Mortality rates
for anorexia nervosa range from 2% to 8%. Mortality
associated with bulimia nervosa appears to be significantly less
than that due to anorexia nervosa.
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One of the keys to successful treatment of eating disorders is
early recognition of the problem and early intervention. Children
and adolescents should be weighed at every medical appointment or
at least once a year to look for weight loss or growth failure.
Longitudinal studies demonstrate that dieting behavior is a risk
factor for the development of eating disorders.25,26 Thus,
clinicians should screen for dieting behavior. Other risk factors include
poor body image27,28 and media exposure.29 Parents,
peers, and clinicians can work to prevent eating disorders by promoting
healthy eating and physical activity habits rather than focusing
on weight or body shape. This can be accomplished by modeling healthy
habits, avoiding diets and negative comments about body weight and
shape, and encouraging family meals and regular exercise. Media
exposure can be limited by parents and/or filtered with
proper supervision in the home and clinic setting, where magazines
and images depicting healthy body types can be selected.