Physiological Aspects of Anorexia Nervosa

According to the American Psychiatric Association, the following criteria are used to diagnose anorexia nervosa: body weight under 85 percent of that expected for height (BMI of less than 17.5) accompanied by an intense fear of gaining weight, denial of the dangers and implication of the low body weight, extreme shape concerns, and loss of three consecutive menstrual periods, if menstruation has begun. There is a further breakdown into restricting type (characterized by food restriction) and purging type (characterized by some caloric restriction along with compensatory behaviors such as overexercise or purging, for example, vomiting or laxative abuse). The physiological consequence of the latter type may include the physiological consequences of both anorexia nervosa as well as those of bulimia nervosa.

Anorexia nervosa is a serious psychological disorder with important and devastating physiological consequences. These consequences are known to include infertility, low bone density, cardiac complications, and truncal fat deposition in refeeding. In addition, low blood pressure, low heart rate, increased heart rate variability, and arrhythmias can lead to cardiac failure both during and following anorexia nervosa. Dehydration and low blood pressure along with increased strain resulting from increased ketone bodies can lead to kidney failure. Liver failure can also result from malnutrition and dehydration. Furthermore, anorexia nervosa can be associated with numerous hormonal changes including decreased levels of estrogen, estradiol, lutenizing hormone, L-3,5,3'-tri-iodothyronine (T3), thyroxine (T4), thyroid stimulating hormone (TSH), leptin, and increased levels of cortisol.

Anorexia nervosa affects approximately 1 percent of the female population and a small percentage of the male population. Despite the relatively low prevalence, the physiological consequences of anorexia nervosa make it one of the most costly and deadly psychological disorders. Partly due to the dire physiological consequences, inpatient treatment for care can exceed $1,000 per day and months of inpatient treatment may be required to achieve medical stability. The vast and potentially devastating physiological consequences along with high suicide rate among persons with anorexia nervosa make this the deadliest psychological disorder.

Physiological consequences of anorexia nervosa can impact a variety of bodily systems and have lasting effects even if full weight recovery is achieved. Persons with anorexia nervosa often suffer from malnutrition, vitamin deficiencies, and mineral deficiencies. The consequences of malnutrition manifest in muscle, bone, and organs. Persons with anorexia nervosa are at risk for osteoporosis, infertility, and cardiac, renal, and liver failure.

Changes in both the skeletal and muscular systems occur. Low body weight and the lack of nutrients seen in anorexia nervosa is associated with the premature development of osteopenia (low bone mineral density leading to increased likelihood of developing osteoporosis over time) and osteoporosis (thin and brittle bones associated with an increased risk breaking bones). Muscular changes can also occur. As the body enters into prolonged starvation, protein from dietary intake and muscle may be broken down as an energy source to supply the brain and other organs with the energy to keep functioning. As a result, muscle loss and weakness are likely to occur. The loss of lean body mass (LBM) may be accompanied by a decrease in resting energy expenditure (REE). The metabolic rate is likely to slow to conserve energy, especially if the anorexia nervosa is present for a prolonged period of time.

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