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How Bulimia Nervosa Affects the Brain

Most people know the basics of bulimia nervosa; the disorder is common enough and portrayed often enough in films, TV, and books that they’ve at least heard of it. Despite this general familiarity, eating disorders like bulimia nervosa aren’t as well understood as they might be. The symptoms of bulimia nervosa go beyond the characteristic binge-and-purge cycle that most people know, and its causes are still being researched.

Sadly, many people outside the medical and psychiatric community have an incomplete understanding of what causes bulimia nervosa and what effects it has on the brain. There is even a persistent notion that disordered eating behaviors are a choice that a person makes. This kind of misguided judgment can prevent people from seeking eating disorder treatment, even when it is needed to save the person’s life.

To truly understand both the causes and effects of bulimia nervosa, it’s important to consider how the disorder affects the brain.

Causes of Bulimia Nervosa

As with most other mental health and psychiatric disorders, there is no single cause of bulimia nervosa. Experts agree that bulimia nervosa is caused by a combination of several factors:

  • Upbringing and Environment

    People whose parents or close relatives suffered from an eating disorder have a much higher chance of developing one themselves. While this may point to a genetic factor to some extent, it’s also clear that when a premium is put on being thin and counting calories at a young age, it affects eating patterns and self-image in later life.

  • Peer Pressure and the Media

    Pressure to fit in and meet societal and cultural standards is a powerful force. Although this could be relatively benign when it comes to things like prevailing hairstyles or clothing, the promotion of a certain “ideal body” can trigger deeply problematic eating behaviors when that ideal is unnaturally skinny. Certain body types are unattainable for the majority of people, and trying to attain them can lead to disordered eating behaviors.

  • Psychiatric Causes

    As we’ll see shortly, there are certain neurochemical factors that can influence a person’s predisposition to develop an eating disorder. These largely center around serotonin, a neurotransmitter associated with a variety of brain and body functions, and also related to mental health disorders like depression.

Although there is no single cause of eating disorders, there are commonalities. Virtually every case of bulimia nervosa coincides with a distorted body image and/or body dysmorphia (a sense of dissatisfaction with one’s body and a misconceived perception of its flaws, especially regarding weight). In a similar vein, researches at clinics and at eating disorder treatment centers around the country have found there are certain responses to psychiatric stimuli that are common in people with bulimia nervosa, but absent in those without.

A Different Response to Stress

In a study performed in 2017, researchers examined several different groups’ responses to food cues (in this case, images of high-fat and high-sugar food) both before and after stress tests.

Their results were surprising.

The study was attempting to discern if there were any differences in the brain’s activity among people with a diagnosis of bulimia nervosa and for a control group who had not. Before conducting the study, each group was given the same meal about an hour prior to beginning the experiment. After the meal, each group of ten was attached to an MRI machine and shown a series of photographs. One set of photos were neutral images like pictures of furniture and tree leaves, and the other set consisted of high-fat “junk” or “comfort” food like pizza and brownies.

For this first part of the experiment, the results were about as expected; the blood flow to the precuneus (a part of the brain associated with self-awareness and thinking about the self) slightly increased after looking at the food cues.

The next part of the experiment centered around increasing stress before showing the food cues again. Participants in the study were tasked with trying to solve a math equation. Unknown to them, the problem was impossible to solve. After a certain amount of time, the participants were asked to rate their stress, and tests were taken to confirm these stress levels. Virtually everyone involved reported increased stress after trying and failing to complete the equation.

The participants were shown a different set of food cues, although the pictures were similar, and again the flow of blood to the precuneus was measured via MRI. This time, the blood flow increased as expected in the people without bulimia nervosa.

For the people with bulimia nervosa, the result was not as expected.

At higher stress levels, looking at pictures of fatty, sugary foods actually decreased in this group. The researchers, seeing this result, came to an interesting conclusion; certain people have a biological predisposition to developing eating disorder symptoms.

Since the precuneus is the part of the brain that deals with self-awareness, and self-criticism, it was expected that stress about a failed task would increase the blood flow to that area. However, by looking at pictures of junk food, the blood flow decreased meaning that food cues reduced the level of self-criticism in the group of participants with bulimia nervosa. This means there is a strong possibility that the binge eating episodes associated with bulimia nervosa reduce the amount of self-criticism this demographic engages in.

Almost every case of an eating disorder is accompanied by a strong sense of self-criticism and perfectionism; feelings of being fat lead to dieting, food restriction, and purges. These facts, all added up, indicate that certain people are genetically predisposed to develop bulimia nervosa.

Neurological Effects on the Brain Caused by Bulimia Nervosa

Bulimia nervosa’s relationship with neurochemistry is not simply one of causation. Eating disorders can have a variety of effects on the brain as well. Repeated binge eating episodes can alter the way the brain releases and distributes serotonin, not to mention the various deficiencies in brain function resulting from prolonged malnutrition.

Serotonin is a neurotransmitter, meaning it is a chemical substance that helps to push forward the electrical impulses sent from the brain through the nervous system. It’s been linked with a variety of neurological functions such as mood and social behavior, appetite and digestion, sleep, memory, and sexual desire and function. Serotonin is also thought to be linked with a variety of mental health disorders, most notably clinical depression.

It’s not clear if low serotonin levels cause depression or are a result of depression, but it’s clear that negative moods, low self-esteem, self-criticism, fatigue, and other signs of depression coincide with low serotonin levels – and the same is true for bulimia nervosa.

Low levels of serotonin can be reconciled with certain activities and drugs. It’s thought that one of the neurological factors in substance abuse and drug addiction is the repeated use of the drug to prompt serotonin release. Exercise, exposure to sunlight, and importantly, eating can also release serotonin.

In regard to bulimia nervosa, the latter item is key to understanding the compulsive and repetitive nature of binge eating and purging behaviors. People with bulimia nervosa routinely engage in binge eating episodes in which they eat a large amount of food in a short time, oftentimes the kinds of junk foods that were shown in the MRI study described above. This creates a “feedback loop” the perpetuates the binge-and-purge cycle.

When the individual’s serotonin level is low, they will binge eat until more serotonin is released, increasing the mood and providing a temporary reprieve from stress and other negative emotions.  However, their negative self-image and feeling of being “fat,” whether or not this is true, will cause them to take compensatory purging actions like self-induced vomiting or laxative abuse. The guilt induced by these actions trigger depression and low serotonin levels, and this in turn causes further binge eating episodes. It’s a dangerous cycle and one which is difficult to escape.

Psychiatric Treatment for Bulimia Nervosa

Eating disorder treatment is normally a combination of therapy, mindful movement exercises such as meditation and yoga, and psychiatric treatments. After a long-term bout of bulimia nervosa or another eating disorder, it’s often necessary to stabilize the individual medically and psychiatrically before moving on to talk therapy and group sessions. Stabilization includes addressing physical symptoms of bulimia nervosa and may include anti-psychotic or anti-depressant drugs if the individual is suicidal or experiencing a psychiatric episode.

In the long run, once the individual has established a regular, nutritional eating pattern with the help of nutritionists and dieticians and eliminated disordered eating behaviors, serotonin levels normally return to normal levels. If they don’t it’s possible to prescribe SSRIs to maintain serotonin equilibrium. In general, however, psychiatric medications aren’t prescribed for eating disorders alone.

The experts and compassionate staff at a quality eating disorder treatment center can fill that gap, however. Through mindfulness training and cognitive training exercises like Cognitive Behavioral Therapy and Dialectical Behavioral Therapy, flawed thinking, and emotional patterns can be identified and corrected. If you or a loved one is suffering from bulimia nervosa, it’s essential not to wait to take action. Reach out to a therapist or doctor you trust or contact Monte Nido to get started on the journey to a recovered life.


Melissa Orshan Spann, PhD, LMHC, RTY 200, is Chief Clinical Officer at Monte Nido & Affiliates, overseeing the clinical operations and programming for over 50 programs across the U.S. Dr. Spann is a Certified Eating Disorder Specialist and clinical supervisor as well as an accomplished presenter and passionate clinician who has spent her career working in the eating disorder field in higher levels of care. She is a member of the Academy for Eating Disorders and the International Association of Eating Disorder Professionals where she serves on the national certification committee, supervision faculty, and is on the board of her local chapter. She received her doctoral degree from Drexel University, master’s degree from the University of Miami, and bachelor’s degree from the University of Florida.