Anorexia nervosa and bulimia nervosa are both eating disorders driven by an intense focus on body weight and shape, but they differ in how that preoccupation plays out. Anorexia centers on persistent restriction of food intake that leads to significantly low body weight. Bulimia centers on repeated cycles of binge eating followed by compensatory behaviors like vomiting or excessive exercise, often at a normal or near-normal weight. The two can overlap, and some people shift from one to the other over time, but they carry distinct physical risks, psychological patterns, and treatment paths.
Core Behaviors in Each Disorder
Anorexia comes in two subtypes. The restricting type involves severe calorie limitation and sometimes compulsive exercise, without regular binge-purge episodes. The binge-eating/purging type includes those same restriction patterns but also involves episodes of bingeing, vomiting, or laxative misuse. In both cases, the defining feature is a body weight that falls well below what’s medically healthy, combined with an intense fear of gaining weight.
Bulimia follows a different cycle. A person eats a large amount of food in a short period, often feeling out of control during the episode, and then tries to compensate. Compensatory behaviors include self-induced vomiting, fasting, excessive exercise, and misuse of laxatives, diuretics, or even newer weight-loss medications like GLP-1 agonists. These binge-compensate cycles happen at least once a week. Severity is graded by how frequently the compensatory behaviors occur: one to three episodes per week is classified as mild, while 14 or more per week is considered extreme.
Body Weight Tells a Different Story
One of the most visible differences is weight. Anorexia is defined partly by significantly low body weight, and severity is categorized by BMI. A BMI of 17 or above is considered mild anorexia, 16 to 16.99 is moderate, 15 to 15.99 is severe, and below 15 is extreme. People with bulimia, by contrast, typically maintain a weight in or near the normal range. This makes bulimia easier to hide and often harder for friends and family to recognize.
That difference in visibility matters. Because people with bulimia don’t “look” underweight, the disorder can go undetected for years. Physical signs like worn tooth enamel, sensitive or decaying teeth, and swollen salivary glands in the jaw and neck area are sometimes the first clues noticed by a dentist or doctor rather than by family.
How They Differ Psychologically
Both disorders involve distorted thinking about food and body image, but the underlying cognitive patterns diverge in important ways. People with anorexia tend to have unusually strong self-control and an ability to delay gratification. Research on decision-making shows that those with active anorexia can resist short-term rewards more effectively than the general population, a trait that reinforces their restrictive behavior. After weight restoration, that heightened self-control tends to normalize.
Bulimia works almost in reverse. People with bulimia show heightened sensitivity to reward and difficulty inhibiting responses to food cues. The brain essentially overvalues the immediate relief that comes from purging (a temporary drop in anxiety) and undervalues the long-term health consequences. This pattern drives the binge-purge cycle: the impulse to eat becomes difficult to stop, and the urge to compensate afterward feels equally compelling.
Both conditions involve cognitive rigidity, meaning difficulty shifting between tasks or mental strategies. This inflexibility is most pronounced in people who experience mixed symptoms of restriction and bingeing. Importantly, these cognitive differences appear to be tied to the active illness rather than being permanent traits. After recovery, thinking patterns on decision-making and flexibility tasks look similar to those of people who never had an eating disorder.
Physical Health Risks
Anorexia’s most dangerous consequences stem from prolonged starvation. The body begins breaking down its own tissue for energy, which can weaken the heart muscle, thin the bones, and cause a fine layer of body hair (called lanugo) to grow as the body tries to insulate itself. Severe malnutrition disrupts nearly every organ system. Anorexia carries one of the highest mortality rates of any psychiatric illness, largely because of these cascading physical effects.
Bulimia’s physical toll is concentrated around the purging behaviors. Repeated vomiting erodes tooth enamel, irritates the esophagus, and causes the salivary glands to swell visibly. The more systemic danger comes from electrolyte imbalances. Purging depletes essential minerals like potassium, sodium, and magnesium, which can lead to dangerous heart rhythm disturbances. A large population-based study found that people with eating disorders who developed electrolyte abnormalities had significantly higher rates of hospitalization (about 60% compared to 47% in matched controls), acute kidney injury, chronic kidney disease, and bone fractures.
Both disorders can cause these electrolyte problems, but the mechanism differs. In anorexia, the imbalance typically comes from not taking in enough nutrients. In bulimia, it comes from losing nutrients through vomiting or laxative abuse. Either way, the downstream risks to the heart and kidneys are serious.
Who Is Affected
Both disorders most commonly appear in adolescence and young adulthood. The highest rates of new diagnoses occur in the 15 to 19 age range, while the greatest burden of ongoing illness peaks between ages 20 and 24. Bulimia is significantly more common than anorexia. Prevalence estimates put bulimia at roughly 0.6% of the population compared to just 0.01% for anorexia, though these numbers likely undercount both conditions since many people never seek treatment.
While eating disorders are diagnosed more often in women, they affect people of all genders. Research on health outcomes like electrolyte complications has found consistent patterns across sexes and across different eating disorder types, suggesting the medical risks are not limited to any single demographic.
Overlap Between the Two
The line between anorexia and bulimia is not always clean. Anorexia’s binge-eating/purging subtype involves the same compensatory behaviors seen in bulimia, including vomiting and laxative misuse. The key diagnostic distinction is weight: if a person is significantly underweight and bingeing/purging, the diagnosis is anorexia (binge-eating/purging type). If they are at or near a normal weight, it’s bulimia.
Many people also move between diagnoses over time. Someone who begins with anorexia may later develop binge-eating patterns and shift toward bulimia, or vice versa. This crossover is common enough that clinicians think of eating disorders as existing on a spectrum rather than as entirely separate conditions.
Treatment Approaches
The first-line treatments differ for each disorder, reflecting their distinct behavioral patterns. For bulimia, enhanced cognitive behavioral therapy (CBT-E) is the most well-supported approach. It targets the thoughts and feelings that fuel binge-purge cycles, helps establish regular eating patterns, and then works on the deeper cognitive distortions about weight and shape. Dialectical behavioral therapy has also shown effectiveness for binge eating and some bulimia symptoms, particularly for people who struggle with emotional regulation.
For anorexia, especially in adolescents, family-based treatment is considered the leading approach. Parents and family members take an active role in helping restore healthy eating patterns and weight, gradually handing control back to the person as they recover. This model recognizes that severe malnutrition impairs the brain’s ability to make sound decisions about food, so external support is essential in early recovery. For adults with anorexia, treatment often combines nutritional rehabilitation with therapy, and in severe cases may require medical stabilization in a hospital or residential program.
Recovery timelines vary widely. Bulimia often responds to outpatient therapy within months, though relapse is common without sustained follow-up. Anorexia typically requires longer treatment, particularly when weight needs to be restored gradually under medical supervision. In both cases, the cognitive improvements that come with recovery are encouraging: the rigid thinking patterns and impaired decision-making associated with active illness tend to resolve as physical health is restored.