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Anorexia nervosa and brain fog: What is it?

Anorexia nervosa (AN) is a serious mental health condition, which can manifest as any number of complications. And while the eating disorder is often connected to weight and the physical body, it can have just as much of an impact on the mind, causing issues like brain fog.

 minute read
Last updated on 
August 14, 2023
December 27, 2023
Anorexia and brain fog
In this article

What is brain fog? 

“Brain fog” is not a medical term, but rather a phrase commonly used to describe a suite of symptoms that are related to mild cognitive impairment.

Some sensations sometimes described as brain fog include:1

  • Slow thinking
  • Difficulty focusing
  • Confusion
  • Difficulty concentrating or lack of concentration
  • Forgetfulness
  • A sense of “haziness” when thinking

When these conditions persist for 6 months or more, it’s generally referred to as chronic fatigue syndrome (CFS).1

The exact cause of brain fog or CFS is unknown and can vary from case to case, but it’s thought that some of these effects are related to blood flow issues in the brain and inefficient activation of certain areas of the brain, particularly those involved in information processing, attention, concentration, and memory performance.1

When brain fog symptoms last for 6 months or longer, it is known as chronic fatigue syndrome.

How does anorexia nervosa contribute to brain fog? 

While AN may not lead to brain fog symptoms directly, some consequences of the disordered eating patterns involved can contribute to brain fog and related issues.

Anorexia nervosa, blood sugar, and brain fog

The brain is the central command post of the body, and all that processing power requires a good deal of energy. By some estimates, the brain uses as much as 20% of the body’s available energy to run.2 And that energy comes from food—or, more specifically, the glucose found in food.

Appropriate glucose levels are a particularly big priority for the brain, as the organ is unable to synthesize or store energy, as other organs or muscles can, and must instead rely on a consistent outside source of the fuel.2 That can become problematic when someone is struggling with AN.

A key aspect of the disorder is the extreme limitation of food intake, and this can have a big impact on blood sugar levels. Hypoglycemia, or low blood sugar, is common among people with AN, especially when AN is advanced.3

And while hypoglycemia frequently has more immediate—and potentially very dangerous—effects, some studies suggest it may also contribute to longer-term problems with cognitive functioning, including issues with memory and attention span, which may feel like or be described as brain fog.4


Anorexia nervosa, malnutrition, and brain function

Another common consequence of the restricted diet involved with anorexia nervosa, and particularly in cases of severe anorexia nervosa, is malnutrition. Low or inappropriate levels of certain vitamins, minerals, and nutrients can wreak havoc on nearly every internal system in the body, including many processes in the brain.

Studies on the subject have linked malnutrition in children to cognitive symptoms like poor attention span and working memory, trouble with learning, and issues with visual perception and spatial relationships between objects.5

Conversely, it's been found that a properly nutritious diet can prevent or even reverse some of these effects, including in people who were previously malnourished.5,6

Anorexia and brain fog

How does anorexia nervosa impact the brain?

The malnutrition and glucose deficits often brought on by anorexia nervosa can impact the brain in other ways.

The organ is primarily made up of two types of tissue: Grey matter and white matter. Grey matter contains most of the circuitry of the brain, while white matter essentially functions as insulation for these circuits. But AN may be directly tied to changes in this brain structure.

Studies on the subject have found reduced grey matter in patients with AN. Some examinations found that white matter also shrunk in these subjects, though those results were not as consistent.7 And the impact was generally found throughout nearly the entire cerebral cortex - the area of the brain responsible for reasoning, thought, and memory, among other essential functions.8

Still, these studies, too, found that many of these effects were reversible with weight restoration, with many patients regaining grey matter levels as they proceeded with treatment and achieved a healthy body weight.7

Brain fog can come from many sources, including stress, fatigue, malnutrition, and mood disorders.

How to prevent brain fog

As brain fog can come from many sources—including stress, fatigue, and certain mood disorders, as well as malnutrition caused by AN and other eating disorders—there are many ways to help alleviate these effects.

Simply allowing yourself to sleep, rest, or take breaks, especially from the draining demands of technology and social media, can all help the brain recalibrate and replenish supplies of focus, concentration, or memory. Meditation, walks outside, short naps, or even creative pursuits can all further aid in these mental resets. 

Of course, eating a nutritious diet and staying well-hydrated can also help bolster cognitive function. This includes staying away from low-grade drugs like caffeine and alcohol.

But the best way to reduce the symptoms of brain fog for someone simultaneously struggling with anorexia nervosa is to address the eating disorder directly. AN is a dangerous and debilitating condition, and it can have far worse consequences than brain fog if left untreated.

Finding treatment for anorexia

If you or a loved one are struggling with anorexia nervosa, it’s important to seek out help.

The good news is that treatment for anorexia is widely available. A number of therapeutic methods, medications, and other types of care have been developed to help people overcome this eating disorder.

Speaking with your primary care physician, therapist, or another trusted medical professional may be a good place to start looking for help. These experts may be able to help you secure a proper diagnosis, opening up pathways to covered care, or direct you to successful treatment programs.

Remote treatment for anorexia nervosa

At Within Health, we also strive to help people struggling with anorexia nervosa, as well as those dealing with bulimia nervosa (BN), binge eating disorder (BED), and other eating disorders. Our multidisciplinary team can offer many different types and levels of care, creating a treatment plan that’s tailored to your specific needs, to help ensure your road to recovery is as smooth as possible.

Call (866) 293-0041

Disclaimer about "overeating": Within Health hesitatingly uses the word "overeating" because it is the term currently associated with this condition in society, however, we believe it inherently overlooks the various psychological aspects of this condition which are often interconnected with internalized diet culture, and a restrictive mindset about food. For the remainder of this piece, we will therefore be putting "overeating" in quotations to recognize that the diagnosis itself pathologizes behavior that is potentially hardwired and adaptive to a restrictive mindset.

Disclaimer about weight loss drugs: Within does not endorse the use of any weight loss drug or behavior and seeks to provide education on the insidious nature of diet culture. We understand the complex nature of disordered eating and eating disorders and strongly encourage anyone engaging in these behaviors to reach out for help as soon as possible. No statement should be taken as healthcare advice. All healthcare decisions should be made with your individual healthcare provider.


  1. Ocon, A. J. (2013). Caught in the thickness of brain fog: Exploring the cognitive symptoms of chronic fatigue syndrome. Frontiers in Physiology, 4.
  2. Mergenthaler, P., Lindauer, U., Dienel, G. A., & Meisel, A. (2013). Sugar for the brain: the role of glucose in physiological and pathological brain function. Trends in Neurosciences, 36(10), 587–597.
  3. Mehler, P. S., & Brown, C. (2015). Anorexia nervosa - medical complications. Journal of Eating Disorders, 3, 11.
  4. The effect of diabetes on the brain. Centers for Disease Control. Accessed July 2023. 
  5. Kar, B. R., Rao, S. L., & Chandramouli, B. A. (2008). Cognitive development in children with chronic protein energy malnutrition. Behavioral and Brain Functions, 4, 31.
  6. Spencer, S. J., Korosi, A., Layé, S., Shukitt-Hale, B., & Barrientos, R. M. (2017). Food for thought: how nutrition impacts cognition and emotion. NPJ Science of Food, 1, 7.
  7. Kaufmann, L.-K., Hänggi, J., Jäncke, L., Baur, V., Piccirelli, M., Kollias, S., Schnyder, U., Martin-Soelch, C., & Milos, G. (2020). Age influences structural brain restoration during weight gain therapy in anorexia nervosa. Translational Psychiatry, 10(1).
  8. Cerebral Cortex. (n.d.). Cleveland Clinic. Accessed July 2023.


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