The differences between bulimia nervosa and anorexia nervosa

What is anorexia nervosa?

Anorexia nervosa is a diagnosable condition in which an individual severely restricts food intake. The cognitive reasons for restricting may vary, but are most usually a result of unhealthy thought patterns or perceptions of one’s own body or a desire to maintain control by limiting caloric intake. When AN progresses from moderate to severe, the individual can experience medical and physical consequences of starvation.¹

In many cases, the restrictive eating behaviors of anorexia nervosa will present as someone continually declining to eat, possibly by telling others they’ve already eaten or aren’t feeling hungry. It’s not uncommon for people struggling with AN to skip out on social occasions involving food all together.

The person may engage in food-related rituals and other notable eating habits, including pushing food around their plate but not taking any bites of it, eating food in certain orders, or only taking big or tiny bites of what they’re eating. Restrictive eating behaviors can also manifest as extreme control over one’s diet, through methods like keeping a strict eye on calorie counts, portions, or nutritional content in order to prevent weight gain.

And concerns over weight gain and poor self-esteem and body image can frequently look like a fixation on the topics of body weight, size, shape, or appearance, whether in general or about the person in particular. Sensitivity and visible distress around these topics is also common in people with AN.

What is bulimia nervosa?

There are actually two different medically-classified types of bulimia nervosa, but the general disordered eating pattern tying them together is a cycle of binging and purging. It can be helpful to define “binging” and “purging” separately. 

“Binging” is when a person eats, within a 2-hour window, an amount of food that is definitively larger than what most people would eat in a similar timeframe. This can be anything from eating a heavy meal to eating thousands of calories at a time, depending on severity. During these episodes, patients usually describe feeling “out of control” and they just cannot stop eating.²

“Purging” refers to the compensatory behaviors people perform to make up for the binging episodes. This type of behavior is medically considered part of bulimia nervosa disorder when it happens at least once a week, for at least three months. 

Bulimia nervosa is defined as binging episodes with or without purging. Purging can manifest in a number of different forms, and the method(s) a person most frequently uses is what dictates the type of BN disorder they’re diagnosed with. “Purging” type of bulimia nervosa is when someone physically expels the food from their body, either through self-induced vomiting or misuse of laxatives or other diuretics, or excessive exercise.²

The way these behaviors play out in real life can vary widely. People may utilize one or several types of purging behavior, or switch between “purging” and “nonpurging” episodes. Often, people with bulimia nervosa hide their binging episodes, declining to eat with or around others, or binging food late at night. 

Anorexia vs. bulimia

Bulimia nervosa and anorexia nervosa share many commonalities, though the conditions ultimately present differently, may have different biological or psychological origins, or impact people in different ways.

Anorexia and bulimia: differences

Aside from the different disordered eating patterns exhibited by anorexia nervosa and bulimia nervosa, the biggest difference between the two conditions is the psychological and physiological mechanics behind those behaviors.

Most experts hypothesize that anorexia is not necessarily just about distorted body image, but is also, if not more so, a maladaptive coping mechanism to attempt to feel a sense of control. People struggling with anorexia nervosa tend to exert control over what they eat as an attempt to gain a sense of control over their life or their emotions. This is sometimes a learned response to traumatic events in their past or stressful circumstances in their present.¹

Bulimia, in contrast, is thought to be more of a coping mechanism for stress management. Patients often binge for the pleasure it provides and the way it relieves stress. 

One study on the subject found that a significant number of people with bulimia nervosa experienced disruptions in the neurological pathways responsible for motivation and reinforcement – the same neurological pathways behind the feelings of hunger and satiety.³ Studies have found that once a person starts engaging in binging and purging behaviors, those pathways can become more dysfunctional, with the body “learning” to release floods of feel-good chemicals any time a person eats, especially when the food involved is high in fat, carbohydrates, and sucrose.³

When this happens, it can override the reward center of the person’s brain, leading to the sensation of losing control during binging episodes. A mixture of guilt, sadness, anxiety, depression, and other negative emotions following these episodes is usually what drives the compensatory purging behaviors.

Anorexia and bulimia: similarities

Among their many similarities, bulimia nervosa and anorexia nervosa primarily share a number of common risk factors.

Both BN and AN have been found to be at least moderately hereditary. People with an immediate family member—such as a parent, sibling, or aunt or uncle—presenting with either disorder are at particularly high risk of inheriting genes that potentially make them more likely to develop bulimia nervosa or anorexia nervosa.⁴

It’s also possible for someone to inherit a number of personality traits or characteristics that make them more susceptible to experiencing either condition, including perfectionism, fearfulness, pessimism, doubtfulness, shyness, a tendency to worry, and certain reactions to stress.⁴

Many people with bulimia nervosa and anorexia nervosa also experience co-occurring mental disorders. Depression and anxiety disorders of many types have particularly strong connections to both anorexia nervosa and bulimia nervosa. 

Other common factors between the two conditions include poor self-esteem, a marked fear of weight gain, and overall dissatisfaction with body image. A history of childhood trauma or abuse is also common among patients with either condition. 

The two conditions also share a number of overlapping signs and eating disorder symptoms. Mood swings, weight loss, thinning hair, poor dental health, and other signs of malnutrition are common in people struggling with both conditions.

Restriction and binge eating in other disorders

There are other similar eating disorders that have been described.

Avoidant restrictive food intake disorder

Avoidant Restrictive Food Intake Disorder (ARFID) is characterized by the same restrictive eating behavior as anorexia nervosa, with the primary difference being the motivations behind that behavior. People struggling with ARFID typically refuse certain foods more out of a distaste for certain textures or smells or a fear of choking, rather than a fear of gaining weight or a desire to “control” their bodies. 

Binge eating disorder

Binge eating disorder (BED) shares a number of characteristics with both anorexia nervosa and bulimia nervosa. While people struggling with BN engage in disordered eating patterns that resemble binge eating behavior, the psychological driver behind them is typically a restrictive mindset in BN: Attempts to restrict their food intake are often what leads to subsequent binging episodes.

Exercise addiction, though not technically classified as an eating disorder, hinges on the act of excessively working out, which can also present as a purging behavior.

Night eating syndrome

Night eating syndrome (NES) experience some aspects of binging behavior, such as feeling a loss of control when eating, which can lead to episodes of overeating, particularly late at night. (5)

All of these conditions have a lot of overlap, and sometimes we over focus on “labeling” them instead of focusing on the individual's needs. The main reason for categorizing these various conditions is to help us identify which thoughts and fears are driving maladaptive behavior patterns so that we can best address the therapeutic needs of the individual patient.

When to seek help for an eating disorder

While eating disorders like bulimia nervosa and anorexia nervosa may seem daunting to overcome, it’s never too late to seek help. In fact, the best time to act is usually as soon as possible.

Your primary care physician, therapist, or another trusted medical professional may be able to help you attain an official diagnosis or determine and navigate the best next steps. A number of eating disorder hotlines are also available, offering additional information and resources on these conditions.

But no matter where you start your recovery journey, the most important thing to remember is that recovery from an eating disorder is always within reach.