Comparing the Effects of Anorexia Nervosa and Bulimia Nervosa

Posted on 01 Dec 2014 20:29

While many people understand the basic differences in behavior among those suffering from anorexia nervosa and bulimia nervosa, they might assume that the physiological effects are the same. After all, whether you starve yourself or gorge and then purge, the result is malnutrition, right? Well, in fact, the physiological effects differ among the two in some marked ways. Of course, it is possible for both disorders to manifest in one person, which would complicate the picture. However, the following are the basic differences in effect between the these two major eating disorders.

Basic Characteristics

Anorexia nervosa is characterized by a compulsive pursuit of thinness and a fear of becoming fat. Self-worth becomes centered on body size and shape and there is a preoccupation with food and control of food intake. According to the DSM-IV, the main symptom of anorexia nervosa is a body weight that is 85% that of the expected body weight. Sufferers have a distinct fear of weight gain despite being quite underweight, and they tend to have a body dysmorphic disorder, a distorted body image, seeing themselves as overweight when they are actually quite thin and underweight. Perceptions of hunger and satiety become distorted and misidentified.

Although avoidance of eating, especially of high calorie foods, is one of the main behaviors of anorexia nervosa, self-induced vomiting, laxative and diuretic abuse, and excessive exercise also can occur. Anorexia nervosa is classified, in fact, into two types, one that restricts food with no active measures to reduce weight, and another that includes purging and active measures to reduce weight.

Bulimia nervosa is characterized by a lack of a sense of control regarding eating and a fear of being overweight. Sufferers go through bouts of binge eating where excessive quantities of food are consumed over a short period of time. Afterwards, sufferers try to counteract this behavior by induced vomiting or use of laxatives (less frequent). Binge eating episodes may be preceded by feelings of stress, tension, boredom, loneliness, depression, or fear. There is a sense of being out of control, and although the binging may relieve these negative feelings for a short time, shame, guilt, and self-hatred often follow.

Although bulimia nervosa patients are preoccupied with weight, body-shape, and food, they are usually normal weight, or even over-weight. Not everyone with a binge-eating disorder is diagnosed as having bulimia nervosa, as not everyone that has episodes of binge eating shows consistent compensating behaviors. Patients with bulimia nervosa, as well as binge eating disorders, often also have depression, obsessive-compulsive disorders, anxiety disorders, substance abuse and personality disorders.

It is quite possible that one individual could be diagnosed with more than one eating disorder over a lifetime, and there can be a continuum of disordered eating over time. However, while many persons with bulimia nervosa have a previous history of anorexia nervosa, bulimia nervosa in persons with normal weight rarely develops into aneroxia nervosa.


Anerexia nervosa (AN) and bulimia nervosa (BN) usually develop during adolescence or young adulthood. Anorexia nervosa is much more common in females, at a ratio of 10:1. The prevalence of AN for young adult women between 14 and 20 years of age is between 0.2 and 0.8%, and diagnoses usually occurs before age 25. Although it is difficult to be sure, the rate of AN may be increasing.

Bulimia nervosa is more common in men than is AN. The prevalence is 1 to 2% for young women, and about 0.2% for young men. It is more common in competitive athletes, ballet dancers, and people in fashion such as fashion models. An increase in the rate of BN has been suggested, but there is not enough evidence to confirm this. BN is more common in Western industrialized nations.

Basic Behaviors

AN: Semi-starvation, perhaps with compulsive exercise. AN is usually preceded by what would appear to be "normal" dieting behavior.

BN: Gorging or binging by consuming up to 12,000 calories in a short amount of time, followed by purging by self-induced vomiting, laxative abuse, emetics, diuretics, or excessive exercise. A person with BN may seem like their life is centered on fasting or dieting behaviors. Binging, however, may well be planned in advance and can occur several times per day.


AN: 85% or less of expected weight. This corresponds to a BMI of around 17.5 for adults.

BN: Weight may be normal or slightly higher than normal. Fluctuations in weight occur.

Emotional Characteristics

AN: Those with AN may enjoy food vicariously. They will tend to deny that they're behavior is abnormal or that they have any problems with food or body image, and go to extreme lengths in this denial. Body image can be severely distorted, and severe mood changes occur with characteristically low self-esteem.

BN: Mood swings as in AN occur, but BN sufferers tend to recognize their behaviors as abnormal more often, and the behaviors themselves lead to further feelings of isolation and self-hating thoughts and behaviors.

Physical Symptoms

AN: A fine, soft downy hair on the face and trunk called lanugo hair, which is similar to the hair one a newborn baby. Brittle hair and nails, dry skin, and cold intolerance.

BN: There may be no outward visible signs. There may be swollen salivary glands in cheeks, and sore knuckles or hands with scars or calluses.

Cardiovascular Effects

AN: Bradycardia (slow heart-rate under 60 BPM), hypotension (low blood pressure), orhtostatic hypotension (also called postural hypotension, a low blood pressure that occurs when suddenly standing up - resulting in a "head rush" or dizzy spell).

BN: Heart Arrhythmia, palpitations, and heart weakness.

Gastrointestinal Effects

AN: Delayed gastric emptying, decreased motility (decreased movement of the digestive system), and severe constipation.

BN: Bloating, constipation, and flatulence. There is a risk of gastric dilation with rupture due to extreme over-consumption.

Endocrine and Metabolic Effects

AN: Sensitivity to cold, fatigue, hypercholesterolemia, hypoglycemia, amenorrhea or menstrual irregularities.

BN: Menstrual irregularities. Dehydration and/or electrolyte imbalances due to vomiting and laxative abuse. Rebound retention of fluid and edema may occur.

Musculoskeletal Effects

AN: Osteopenia (below normal bone mineral density but not low enough for osteoporosis), muscle wasting and muscle weakness.

BN: Dental erosion and muscular weakness.

Nutritional Deficiencies

AN: Protein-calorie malnutrition and various micronutrient deficiencies

BN: Variable.

1. Kirch, Wilhelm. Encyclopedia of Public Health. Vol. 1. New York: Springer, 2008.
2. Dudek, Susan G. Nutrition Essentials for Nursing Practice. Philadelphia: Lippincott Williams & Wilkins, 2006.

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