Anorexia nervosa is a serious eating disorder defined by restricted food intake, an intense fear of gaining weight, and a distorted perception of one’s own body size or shape. It carries the highest mortality rate of any psychiatric disorder, with a standardized mortality ratio of 5.21, meaning people with anorexia are more than five times as likely to die prematurely compared to the general population. Lifetime prevalence reaches up to 4% in females and about 0.3% in males, though some population-wide studies using thorough diagnostic interviews have found rates as high as 6.2% in women.
The Three Core Features
A diagnosis requires three things to be present simultaneously. First, the person restricts their food intake enough to maintain a significantly low body weight for their age, sex, and developmental stage. Second, they experience an intense fear of gaining weight or becoming fat, or they persistently behave in ways that prevent weight gain, even when already underweight. Third, they have a distorted experience of their own body. This can show up as feeling overweight despite being dangerously thin, placing extreme importance on body shape when evaluating self-worth, or simply not recognizing how serious the low weight has become.
That last criterion is one reason anorexia can be so difficult to treat. Many people with the condition genuinely do not see what others see when they look in the mirror.
Restricting Type vs. Binge-Purge Type
Anorexia nervosa has two recognized subtypes. The restricting type involves weight loss through dieting, fasting, or excessive exercise, with no regular episodes of binge eating or purging in the past three months. The binge-eating/purging type involves cycles of binge eating, purging (self-induced vomiting or misuse of laxatives and diuretics), or both, on top of the same low body weight and fear of weight gain.
People sometimes confuse the binge-purge subtype with bulimia nervosa, but the key distinction is body weight. In anorexia, the person is significantly underweight. In bulimia, weight is typically normal or above normal. The subtypes also aren’t permanent categories. Many people shift between restricting and binge-purge behaviors over the course of the illness.
What Happens in the Brain
Anorexia isn’t simply a choice to diet taken too far. Research points to significant disruptions in two key brain chemical systems: serotonin and dopamine. Serotonin influences satiety, impulse control, and mood. Dopamine shapes how the brain processes reward and motivation, including the motivation to eat. In people with anorexia, both systems show measurable impairment, which helps explain why food loses its appeal and why restriction can feel compulsive rather than voluntary.
Brain imaging studies have also identified changes in the prefrontal cortex, the insula, and the amygdala. The insula is particularly important because it tracks the body’s internal states, like hunger and fullness. When this region functions abnormally, a person may literally struggle to sense or interpret their own hunger signals. Researchers have also found that certain patterns of thinking and memory can shrink the brain’s internal representation of the physical self, further distorting body image from the inside out.
Early Warning Signs
The behavioral changes often appear before dramatic weight loss does. Food rituals are among the most telling: cutting food into tiny geometric shapes, separating items on the plate, chewing each bite a specific number of times, counting morsels, eating food group by food group in a rigid order, or diluting food with water to make portions look larger. Meals become noticeably slow, with long pauses between bites.
Other common signs include hiding or secretly discarding food, withdrawing from social meals, wearing loose clothing to disguise weight loss, exercising compulsively even when injured or exhausted, and an increasingly rigid preoccupation with calories, food labels, or “clean eating” rules. Physically, early changes include feeling cold all the time, hair thinning, dry skin, and fatigue.
How Anorexia Affects the Heart
The cardiovascular system is one of the first to show damage. Bradycardia, a dangerously slow heart rate, is the most common heart rhythm abnormality in anorexia, affecting roughly 36% of patients in clinical settings. Heart rates can drop into the 40s, with blood pressure falling low enough to cause dizziness or fainting when standing.
Over time, the heart muscle itself shrinks. Studies using echocardiography have found a 30 to 50% reduction in the mass of the left ventricle in young women with anorexia. That reduction is disproportionate to overall body weight loss, meaning the heart is losing muscle faster than the rest of the body. This can lead to mitral valve prolapse, where a heart valve doesn’t close properly, and pericardial effusion, a buildup of fluid around the heart. Both bradycardia and low blood pressure can be early clinical signs that prompt a closer look for an underlying eating disorder.
Bone Loss and Hormonal Disruption
Bone damage in anorexia is widespread and often underappreciated. Between 50% and 90% of patients develop osteopenia (mild bone thinning), and 20 to 30% progress to full osteoporosis. For a condition that often begins in adolescence, when bones should be building to their peak density, this represents a loss that may never be fully recovered.
The mechanism involves a cascade of hormonal disruptions. Estrogen and testosterone levels drop significantly, removing a key brake on bone breakdown. The body develops a form of growth hormone resistance: growth hormone levels rise, but the downstream signal that actually stimulates bone formation (IGF-1) stays low. Cortisol levels tend to climb, further accelerating bone loss. Leptin, a hormone produced by fat tissue, falls along with body fat, and it plays its own complex role in regulating bone density. Together, these factors create a situation where bone is being broken down faster than it can be rebuilt.
What Recovery Looks Like
Treatment varies by age, but the approach with the strongest evidence for adolescents is family-based treatment, sometimes called the Maudsley method. In this model, parents take an active role in managing their child’s eating and weight restoration, gradually handing control back as the adolescent recovers. In one landmark trial, 90% of adolescent patients receiving family-based therapy achieved good or intermediate outcomes based on weight recovery and symptom reduction, compared to just 18% of those receiving individual therapy alone.
For adults, cognitive behavioral therapy adapted for eating disorders is the most commonly used approach, focusing on the rigid thinking patterns and body image distortions that maintain the illness. Many people also benefit from nutritional counseling and, in some cases, medication to manage co-occurring anxiety or depression.
Weight restoration itself requires careful medical oversight. When someone who has been severely malnourished begins eating again, the body can experience dangerous shifts in electrolytes, particularly phosphorus, magnesium, and potassium. This is known as refeeding syndrome, and it can cause heart failure, seizures, or death if not monitored. For this reason, the early stages of nutritional rehabilitation, especially in severely underweight patients, typically happen under close medical supervision with regular blood work.
Recovery timelines vary widely. Some people recover within a year or two with appropriate treatment. Others cycle through periods of relapse and improvement over many years. Full recovery is possible at any stage, but earlier intervention consistently leads to better outcomes, which is why recognizing those early behavioral warning signs matters so much.