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Anorexia nervosa (AN) is classically defined as a condition in which an abnormally low body weight is associated with an intense fear of gaining weight and distorted cognitions regarding weight, shape, and drive for thinness. This article reviews recent evidence from physiology, genetics, epigenetics, and brain imaging which allow considering AN as an abnormality of reward pathways or an attempt to preserve mental homeostasis. Special emphasis is put on ghrelin-resistance and the importance of orexigenic peptides of the lateral hypothalamus, the gut microbiota and a dysimmune disorder of neuropeptide signaling. Physiological processes, secondary to underlying, and premorbid vulnerability factors—the “pondero-nutritional-feeding basements”- are also discussed.
Anorexia is a psychological and potentially life-threatening eating disorder. Those suffering from this eating disorder are typically suffering from an extremely low body weight relative to their height and body type.It is an eating disorder characterized by low weight, fear of gaining weight, and a strong desire to be thin, resulting in food restriction.Many people with anorexia see themselves as over weight even though they are in fact underweight.If asked they usually deny they have a problem with low weight.Often they weigh themselves frequently, eat only small amounts, and only eat certain foods.Some will exercise excessively, force themselves to vomit, or use laxatives to produce weight loss.
Types of Anorexia Nervosa
There are two common types of anorexia, which are as follows:
- Binge/Purge Type – The person struggling with this type of eating disorder will often purge after eating. This alleviates the fear of gaining weight and offsets some of the guilt of having ingested forbidden, or highly restricted food. The compensatory purge behavior by the individual with Binge/Purge Type anorexia may purge by exercising excessively, vomiting or abusing laxatives.
- Restrictive – The individual suffering from restrictive anorexia is often perceived as highly self-disciplined. They restrict the quantity of food, calories and often high fat or high sugar foods. They consume far fewer calories than are needed to maintain a healthy weight. This is a heartbreaking form of self-starvation.
Causes of Anorexia Nervosa
- Genetics – Changes in specific genes may put certain people at higher risk of anorexia. Those with a first-degree relative — a parent, sibling or child — who had the disorder have a much higher risk of anorexia.
- Dieting and starvation – Dieting is a risk factor for developing an eating disorder. There is strong evidence that many of the symptoms of anorexia are actually symptoms of starvation. Starvation affects the brain and influences mood changes, rigidity in thinking, anxiety and reduction in appetite. Starvation and weight loss may change the way the brain works in vulnerable individuals, which may perpetuate restrictive eating behaviors and make it difficult to return to normal eating habits.
- Transitions – Whether it’s a new school, home or job; a relationship breakup; or the death or illness of a loved one, change can bring emotional stress and increase the risk of anorexia.
- Biological – Although it’s not yet clear which genes are involved, there may be genetic changes that make some people at higher risk of developing anorexia. Some people may have a genetic tendency toward perfectionism, sensitivity and perseverance — all traits associated with anorexia.
- Psychological – Some people with anorexia may have obsessive-compulsive personality traits that make it easier to stick to strict diets and forgo food despite being hungry. They may have an extreme drive for perfectionism, which causes them to think they’re never thin enough. And they may have high levels of anxiety and engage in restrictive eating to reduce it.
- Environmental – Modern Western culture emphasizes thinness. Success and worth are often equated with being thin. Peer pressure may help fuel the desire to be thin, particularly among young girls.
- The effects of the thinness culture in media, that constantly reinforce thin people as ideal stereotypes
- Professions and careers that promote being thin and weight loss, such as ballet and modeling
- Family and childhood traumas: childhood sexual abuse, severe trauma
- Peer pressure among friends and co-workers to be thin or be sexy.
- Irregular hormone functions
- Genetics (the tie between anorexia and one’s genes is still being heavily researched, but we know that genetics is a part of the story).
Clinically important causes
- Acute radiation syndrome
- Acute viral hepatitis
- Addison’s disease
- Atypical pneumonia (mycoplasma)
- Anorexia nervosa
- Anxiety disorder
- Chronic pain
- Chronic kidney disease
- Celiac disease
- Congestive heart failure, perhaps due to congestion of the liver with venous blood
- Crohn’s disease
- Drug addiction
- Hypervitaminosis D
- Hypothyroidism can cause anorexia and weight gain despite the loss of appetite.
- Metabolic disorders, particularly urea cycle disorders
- Mood disorders and the moods which arise from them, both depression and mania
- Sickness behavior
- Superior mesenteric artery syndrome
- Ulcerative colitis
- Zinc deficiency
- Amphetamine , dextroamphetamine , lisdexamfetamine
- Antidepressants can have anorexia as a side effect
- Byetta, a Type II Diabetes drug, will cause moderate nausea and loss of appetite
- Abrupt cessation of appetite-increasing drugs, such as cannabis and corticosteroids
- Methamphetamine (treatment of ADHD and narcolepsy)
- Chemicals that are members of the phenethylamine group. (Individuals with anorexia nervosa may seek them to suppress appetite)
- Stimulants such as caffeine, nicotine, and cocaine
- Topiramate may cause anorexia as a side effect.
- Other drugs may be used to intentionally cause anorexia in order to help a patient preoperative fasting prior to general anesthesia. It is important to avoid food before surgery to mitigate the risk of pulmonary aspiration, which can be fatal.
- Opiates (such as morphine, heroin, oxycodone, etc.) act upon the digestive system and can reduce the physical sensation of hunger in the same way that they reduce physical sensations of pain. They also frequently cause delayed gastric emptying (gastroparesis) and can sometimes lead to changes in metabolism with long-term use.
Symptoms of Anorexia Nervosa
Symptoms may include
- A low body mass index for one’s age and height.
- Amenorrhea, a symptom that occurs after prolonged weight loss; causes menstruation to stop, hair becomes brittle, and skin becomes yellow and unhealthy.
- Fear of even the slightest weight gain; taking all precautionary measures to avoid weight gain or becoming “overweight”.
- Rapid, continuous weight loss.
- Lanugo: soft, fine hair growing over the face and body.
- An obsession with counting calories and monitoring fat contents of food.
- Preoccupation with food, recipes, or cooking; may cook elaborate dinners for others, but not eat the food themselves or consume a very small portion.
- Food restrictions despite being underweight or at a healthy weight.
- Food rituals, such as cutting food into tiny pieces, refusing to eat around others and hiding or discarding of food.
- Purging: May use laxatives, diet pills, ipecac syrup, or water pills to flush food out of their system after eating or may engage in self-induced vomiting though this is a more common symptom of bulimia.
- Excessive exercise including micro-exercising, for example making small persistent movements of fingers or toes.
- Perception of self as overweight, in contradiction to an underweight reality.
- Intolerance to cold and frequent complaints of being cold; body temperature may lower (hypothermia) in an effort to conserve energy due to malnutrition.
- Hypotension or orthostatic hypotension.
- Bradycardia or tachycardia.
- Depression, anxiety disorders and insomnia.
- Solitude may avoid friends and family and become more withdrawn and secretive.
- Abdominal distension.
- Halitosis (from vomiting or starvation-induced ketosis).
- Dry hair and skin, as well as hair thinning.
- Chronic fatigue.
- Rapid mood swings.
- Having feet discoloration causing an orange appearance.
- Having severe muscle tension + aches and pains.
- Evidence/habits of self harming or self-loathing.
- Admiration of thinner people.
- Depression or lethargic stage
- Development of lanugo – soft, fine hair that grows on face and body
- Reported sensation of feeling cold, particularly in extremities
- Avoidance of social functions, family, and friends. May become isolated and withdrawn
Emotional and behavioral symptoms
Behavioral symptoms of anorexia may include attempts to lose weight by
- Severely restricting food intake through dieting or fasting
- Exercising excessively
- Bingeing and self-induced vomiting to get rid of food, which may include the use of laxatives, enemas, diet aids or herbal products
Emotional and behavioral signs and symptoms may include
- Preoccupation with food, which sometimes includes cooking elaborate meals for others but not eating them
- Frequently skipping meals or refusing to eat
- Denial of hunger or making excuses for not eating
- Eating only a few certain “safe” foods, usually those low in fat and calories
- Adopting rigid meal or eating rituals, such as spitting food out after chewing
- Not wanting to eat in public
- Lying about how much food has been eaten
- Fear of gaining weight that may include repeated weighing or measuring the body
- Frequent checking in the mirror for perceived flaws
- Complaining about being fat or having parts of the body that are fat
- Covering up in layers of clothing
- Flat mood (lack of emotion)
- Social withdrawal
- Reduced interest in sex
Diagnosis of Anorexia Nervosa
Anorexia nervosa is classified under the Feeding and Eating Disorders in the latest revision of the Diagnostic and Statistical Manual of Mental Disorders (DSM 5).
Relative to the previous version of the DSM (DSM-IV-TR), the 2013 revision (DSM5) reflects changes in the criteria for anorexia nervosa, most notably that of the amenorrhea criterion being removed.
There are two subtypes of AN
- Binge-eating/purging type – the individual utilizes binge eating or displays purging behavior as a means for losing weight.It is different from bulimia nervosa in terms of the individual’s weight. An individual with binge-eating/purging type anorexia can maintain a healthy or normal weight, but is usually significantly underweight. People with bulimia nervosa on the other hand can sometimes be overweight.
- Restricting type – the individual uses restricting food intake, fasting, diet pills, or exercise as a means for losing weight; they may exercise excessively to keep off weight or prevent weight gain, and some individuals eat only enough to stay alive.
Levels of severity
Body mass index (BMI) is used by the DSM-5 as an indicator of the level of severity of anorexia nervosa. The DSM-5 states these as follows
- Mild: BMI of greater than 17
- Moderate: BMI of 16–16.99
- Severe: BMI of 15–15.99
- Extreme: BMI of less than 15
Investigations of Anorexia Nervosa
Medical tests to check for signs of physical deterioration in anorexia nervosa may be performed by a general physician or psychiatrist, including:
- Complete Blood Count (CBC) – a test of the white blood cells, red blood cells and platelets used to assess the presence of various disorders such as leukocytosis, leukopenia, thrombocytosis and anemia which may result from malnutrition.
- Urinalysis – a variety of tests performed on the urine used in the diagnosis of medical disorders, to test for substance abuse, and as an indicator of overall health
- Chem-20 – Chem-20 also known as SMA-20 a group of twenty separate chemical tests performed on blood serum. Tests include cholesterol, protein and electrolytes such as potassium, chlorine and sodium and tests specific to liver and kidney function.
- Glucose tolerance test – Oral glucose tolerance test (OGTT) used to assess the body’s ability to metabolize glucose. Can be useful in detecting various disorders such as diabetes, an insulinoma, Cushing’s Syndrome, hypoglycemia and polycystic ovary syndrome.
- Serum cholinesterase test – a test of liver enzymes (acetylcholinesterase and pseudocholinesterase) useful as a test of liver function and to assess the effects of malnutrition.
- Liver Function Test – A series of tests used to assess liver function some of the tests are also used in the assessment of malnutrition, protein deficiency, kidney function, bleeding disorders, and Crohn’s Disease.
- Lh response to GnRH – Luteinizing hormone (Lh) response to gonadotropin-releasing hormone (GnRH) Tests the pituitary glands’ response to GnRh a hormone produced in the hypothalamus. Hypogonadism is often seen in anorexia nervosa cases.
- Creatine Kinase Test (CK-Test) – measures the circulating blood levels of creatine kinase an enzyme found in the heart (CK-MB), brain (CK-BB) and skeletal muscle (CK-MM).
- Blood urea nitrogen (BUN) test – urea nitrogen is the byproduct of protein metabolism first formed in the liver then removed from the body by the kidneys. The BUN test is primarily used to test kidney function. A low BUN level may indicate the effects of malnutrition.
- BUN-to-creatinine ratio – A BUN to creatinine ratio is used to predict various conditions. A high BUN/creatinine ratio can occur in severe hydration, acute kidney failure, congestive heart failure, and intestinal bleeding. A low BUN/creatinine ratio can indicate a low protein diet, celiac disease, rhabdomyolysis, or cirrhosis of the liver.
- Electrocardiogram (EKG or ECG) – measures electrical activity of the heart. It can be used to detect various disorders such as hyperkalemia
- Electroencephalogram (EEG) – measures the electrical activity of the brain. It can be used to detect abnormalities such as those associated with pituitary tumors.
- Thyroid Screen TSH, t4, t3 – test used to assess thyroid functioning by checking levels of thyroid-stimulating hormone (TSH), thyroxine (T4), and triiodothyronine (T3).
According to the American Psychiatric Association’s (APA’s) Diagnostic and Statistical Manual of Mental Disorders 5th Edition (DSM-5), the diagnostic criteria for anorexia nervosa are as follows-
- Restriction of energy intake relative to requirements leading to a significantly low body weight in the context of age, sex, developmental trajectory, and physical health.
- Intense fear of gaining weight or becoming fat, even though underweight.
- Disturbance in the way in which one’s body weight or shape is experienced, undue influence of body weight or shape on self-evaluation, or denial of the seriousness of the current low body weight.
The National Eating Disorders Association (NEDA) note that even without meeting all these criteria, a person may have a serious eating disorder.
Treatment of Anorexia Nervosa
Acute pharmacologic treatment of anorexia nervosa is rarely required. However, vitamin supplementation with calcium should be started in patients, and although estrogen has no established effect on bone density in patients with anorexia nervosa, estrogen replacement (ie, oral contraceptives) has been recommended for the treatment of osteopenia; the benefits and minimal effective dose of the hormone are being explored.
Types of Psychological Therapy
Various psychological therapies have proven helpful in treating patients with anorexia nervosa, including the following
Individual therapy (insight-oriented)
Enhanced cognitive-behavioral therapy
Motivational enhancement therapy
Dynamically informed therapies
Specialist supportive clinical management
Conjoint family therapy
Separated family therapy
Relatives and caregiver support groups
These types of therapy may be beneficial for anorexia:
- Family-based therapy – This is the only evidence-based treatment for teenagers with anorexia. Because the teenager with anorexia is unable to make good choices about eating and health while in the grips of this serious condition, this therapy mobilizes parents to help their child with re-feeding and weight restoration until the child can make good choices about health.
- Individual therapy – For adults, cognitive behavioral therapy — specifically enhanced cognitive behavioral therapy — has been shown to help. The main goal is to normalize eating patterns and behaviors to support weight gain. The second goal is to help change distorted beliefs and thoughts that maintain restrictive eating.
- Group Therapy – Group therapy allows people with anorexia nervosa to interact with others who have the same disorder. But it can sometimes lead to competition to be the thinnest. To avoid that, it’s important that you attend group therapy that is led by a qualified medical professional.
Complications of Anorexia Nervosa
Complications can affect every body system, and they can be severe.
Physical complications include
- Cardiovascular problems – These include low heart rate, low blood pressure, and damage to the heart muscle.
- Blood problems – There is a higher risk of developing leukopenia, or low white blood cell count, and anemia, a low red blood cell count.
- Gastrointestinal problems – Movement in the intestines slows significantly when a person is severely underweight and eating too little, but this resolves when the diet improves.
- Kidney problems – Dehydration can lead to highly concentrated urine and more urine production. The kidneys usually recover as weight levels improve.
- Hormonal problems – Lower levels of growth hormones may lead to delayed growth during adolescence. Normal growth resumes with a healthful diet.
- Bone fractures – Patients whose bones have not fully grown yet have a significantly higher risk of developing osteopenia, or reduced bone tissue, and osteoporosis, or loss of bone mass.
Around 1 in 10 cases are fatal. Apart from the physical effects of poor nutrition, there may be a higher risk of suicide. One in 5 deaths related to anorexia is from suicide.