Anorexia nervosa and bulimia nervosa are two distinct eating disorders that share some psychological roots but differ in how they manifest in the body and in behavior. Anorexia centers on severe food restriction and dangerously low body weight, while bulimia involves cycles of binge eating followed by purging. Both carry serious medical risks, and globally, eating disorder rates among young people have risen steadily, reaching roughly 355 per 100,000 people aged 10 to 24 as of 2021.
What Anorexia Nervosa Looks Like
Anorexia nervosa is defined by three core features: restricting food intake to the point of significantly low body weight, an intense fear of gaining weight even while underweight, and a distorted perception of one’s own body. Someone with anorexia may look emaciated yet genuinely believe they are overweight. This isn’t vanity or willpower. It’s a persistent disturbance in how the brain processes self-image.
Anorexia has two subtypes. The restricting type involves pure calorie limitation, with no binge eating or purging over the previous three months. The binge-eating/purging type involves episodes of bingeing or purging (vomiting, laxatives, diuretics) alongside the same dangerously low weight. This second subtype can blur the line with bulimia for people unfamiliar with the diagnoses, but the key distinction is weight: a person with anorexia is significantly underweight.
What Bulimia Nervosa Looks Like
Bulimia nervosa follows a different pattern. A person eats large amounts of food in a short period, feels a loss of control during the episode, and then tries to compensate. Compensation can mean self-induced vomiting, misuse of laxatives or diuretics, fasting, or excessive exercise. For a diagnosis, these binge-purge cycles need to occur at least once a week.
The critical difference from anorexia is weight. People with bulimia typically maintain an average weight or may be overweight. Because they don’t look visibly unwell, bulimia often goes undetected for years. The damage is largely internal.
How They Differ at a Glance
- Body weight: Anorexia involves significantly low body weight. Bulimia does not.
- Primary behavior: Anorexia is driven by restriction. Bulimia is driven by binge-purge cycles.
- Visibility: Anorexia often produces visible emaciation. Bulimia is frequently hidden behind a normal appearance.
- Brain reward patterns: Research from the National Institute of Mental Health shows that in anorexia, the brain’s reward signaling may actually reinforce the ability to ignore hunger cues, strengthening food-control circuits. In bulimia and binge eating, the opposite occurs: reward responses are dampened, which may fuel the loss-of-control feeling during binges.
What Anorexia Does to the Body
Prolonged starvation affects nearly every organ system. The heart muscle physically shrinks, a process called myocardial atrophy, which reduces the heart’s pumping capacity and commonly leads to mitral valve prolapse. As BMI drops below 15, pronounced slowing of the heart rate and low blood pressure become almost universal. Fluid can accumulate around the heart, though this typically resolves with weight restoration.
Bone loss is one of the most lasting consequences. Anorexia causes severe drops in bone mineral density that can produce osteoporosis even in teenagers. Unlike many other complications, this damage may be permanent. The combination of elevated stress hormones, low sex hormones, low body weight, and resistance to growth hormone creates a state where bone breaks down faster than it rebuilds. Years after recovery, the risk of fractures remains elevated.
The endocrine system essentially regresses. Most women with anorexia lose their menstrual periods due to plummeting estrogen levels; men experience low testosterone. The thyroid slows down as the body tries to conserve energy, and stress hormone levels stay chronically high. Fine, downy hair called lanugo may appear on the body as it attempts to insulate itself against heat loss.
Anorexia carries the highest mortality rate of any psychiatric illness. Studies tracking patients over roughly a decade have found death rates nearly ten times what would be expected in the general population of the same age.
What Bulimia Does to the Body
The medical toll of bulimia is concentrated around the effects of repeated purging. Electrolyte imbalances, particularly low potassium, are the most common cause of serious illness and death in bulimia. Low potassium disrupts the electrical signaling of the heart, potentially triggering dangerous arrhythmias. Chronic dehydration from purging creates a cycle where the body overcompensates by retaining fluid, leading to rapid swelling when purging stops.
The digestive system takes direct damage. Repeated vomiting bathes the esophagus in stomach acid, weakening the valve at its base and increasing the risk of chronic acid reflux. Over time, this can cause changes to the esophageal lining that raise the risk of cancer. In rare cases, the force of vomiting tears the esophagus itself, a medical emergency.
Teeth suffer irreversible erosion. Acidic vomit, with a pH around 3.8, dissolves enamel on the inner surfaces of the upper teeth. Once that enamel is gone, it doesn’t regenerate. Cavities become more frequent, and the damage is often one of the first clues a dentist notices. Calluses on the knuckles of the dominant hand, sometimes called Russell’s sign, develop from repeated contact with the teeth during self-induced vomiting. These thickened patches of skin can persist long after the behavior stops.
Psychological Patterns Behind Both Disorders
Both anorexia and bulimia involve a disproportionate link between self-worth and body shape or weight. This isn’t simply about appearance. It reflects deeply ingrained patterns of thinking where control over food becomes a proxy for control over life, emotions, or identity. People with anorexia often don’t recognize the seriousness of their condition, which is part of the diagnostic criteria itself, not just denial.
Brain imaging research reveals that the two disorders alter reward circuits in opposite directions. In anorexia, the brain’s reward center sends stronger-than-normal signals that reinforce restrictive behavior, essentially rewarding the person for not eating. In binge-type disorders, reward signals are blunted, meaning normal satisfaction from food doesn’t register properly, which may drive the compulsion to keep eating. In both cases, the normal connection between the brain’s reward system and its hunger-regulation center runs in the wrong direction compared to people without eating disorders.
Who Is Affected
Eating disorders affect people of every gender, age, and background, though rates are highest among adolescents and young adults. Women still account for the majority of diagnoses, but the rate of increase among men is now faster, suggesting the gap is narrowing. While prevalence data is strongest for people aged 10 to 24, both conditions can develop at any point in life, and late-onset cases are increasingly recognized.
Treatment and Recovery
Treatment typically involves psychological therapy, with cognitive behavioral therapy being the most widely studied approach for both disorders. For anorexia in younger patients, family-based therapy, where parents take an active role in restoring their child’s eating, is a front-line option. A more structured approach called the Maudsley model is used for adults with anorexia. Some medications are used off-label to support recovery, though none are considered a standalone treatment for either condition.
Recovery is possible, but the path is rarely straightforward. With the best available treatments, roughly 20 to 30 percent of people do not respond adequately and develop a long-term, treatment-resistant form of illness. This doesn’t mean treatment is futile for these individuals, but it underscores that eating disorders are serious psychiatric conditions, not phases or lifestyle choices. Early intervention consistently improves outcomes, and the physical complications of both disorders are more reversible the sooner treatment begins.