Have you ever felt like your head was truly in the clouds? Like you were more than a little forgetful, had trouble concentrating and sometimes couldn’t find the right words? If so, you may have experienced what is commonly known as “brain fog.” What you might not know is that poor metabolic health could be part of the problem. We’ll explore many factors, such as what causes brain fog, its connection to metabolic health and potential ways to prevent it.

What is brain fog?

Brain fog is not technically a medically diagnosed, stand-alone condition, but it is a term used for symptoms that can affect your mental “sharpness” or ability to think, and it can manifest in many ways. Commonly reported symptoms of brain fog include:

• Hazy, scattered, or muddled thoughts
• Forgetting names, dates, common words
• Difficulties with multitasking
• Reduced attention span and focus
• Lack of concentration
• Misplacing objects/disorganization
• Short-term memory lapses

What causes brain fog?

Although brain fog is a common phenomenon, it is difficult to pinpoint an answer to the question, “What causes brain fog”? The origins of brain fog are multifactorial and are attributed to many different physical conditions. Brain fog is included as a possible symptom of many chronic diseases — including diabetes, depression/anxiety, heart disease and autoimmune disorders (such as Lyme disease and chronic fatigue). Other causes of brain fog may include:

• Interactions between or side effects of medications
• Chemotherapy treatments (this type of brain fog is referred to as “chemo brain")
• Hormonal changes (such as during pregnancy or menopause)
• Stress
• Food allergies/sensitivities
• Insufficient nutrient intake (such as low vitamin B12)
• Impaired gut health
• Infections and viruses (such as COVID-19)
• Lack of sleep

How can metabolic health impact brain fog?

In addition to the underlying medical conditions and causes of brain fog listed above, a hazy brain may also relate to poor metabolic health. While some people may associate metabolic health primarily with the maintenance of an ideal weight, in actuality, metabolic health takes into account five measurable factors that show how healthy you are now, as well as how likely you are to develop serious chronic conditions later in life: blood sugar, waist circumference (BMI), blood pressure, cholesterol and triglycerides. And while many of us are going around feeling just fine, we aren’t as healthy as we might think. In fact, according to a 2019 study, only 12% of American adults are considered metabolically healthy. Learn more: The Basics of Metabolic Health.

Metabolic syndrome (MetS)

If you have three or more of the following conditions, clinicians may diagnose you as having metabolic syndrome (MetS), which puts you at much greater risk of heart disease, stroke, and diabetes. To lesser or greater degrees, each of these conditions can trigger or contribute to brain fog, in the following ways:

• Obesity
  
  Adverse effects of obesity on the brain and central nervous system have been widely studied. A 2020 review suggests that obesity is associated with cognitive deficits, which refer to diminished or impaired mental and/or intellectual functioning. A 2015 review suggests that brain fog associated with obesity may be due to inflammatory molecules released from adipose tissue and histamine released from mast cells, actions that cause inflammation in the brain tissues. Inflammation in adipose tissue associated with obesity has been linked to insulin resistance.

• Insulin Resistance
  
  Insulin is produced by the beta cells in the pancreas and is necessary for moving glucose into cells throughout the body. Most receptors are in target tissues (i.e., liver, skeletal muscles, adipose tissue), but they are also located in the areas of the brain responsible for cognitive function. Insulin resistance is a condition in which the action of insulin is impaired and the body can’t move glucose into the cells, so blood glucose levels stay chronically high. A 2019 mini-review indicated a strong relationship between systemic insulin resistance and higher incidence of mild cognitive impairment, including brain fog.

• High Blood Pressure
  
  Also called hypertension, high blood pressure is well established as the leading risk factor for stroke and has emerged as a pathogenic factor in cognitive impairment. A 2019 review provided an assessment of the effects of hypertension on cognitive function with the epidemiological data suggesting that the greatest impact is on motor speed, attention and executive functioning.

• Impaired Glucose Tolerance or Diabetes
  
  Glucose plays an essential role in fueling the brain, so logically it makes sense that impaired glucose tolerance and type 1 and type 2 diabetes could affect cognitive health. The brain does not store energy to be metabolized into glucose the way the liver and muscles do; instead, the flow of glucose to the brain is tightly controlled by the blood-brain barrier. Both hyperglycemia (high blood glucose) and hypoglycemia (yup, you guessed it, low blood glucose) have been associated with an inability to think clearly, poor attention, memory lapses and other complaints that are described as brain fog. In addition to affecting fuel to the brain, impaired glucose tolerance may affect brain anatomy, causing the hippocampus (important for learning and memory) to shrink and leading to episodic memory impairment, a common brain fog attribute. 

• Hyperinsulinemia and Dyslipidemia
  
  Hyperinsulinemia, an early indicator of metabolic dysfunction, results when the pancreas produces too much insulin to which the body does not respond, aka insulin resistance. Hyperinsulinemia is not considered type 2 diabetes if it is the only symptom, but the two are certainly linked. Environmental, genetic, lifestyle, and dietary factors contribute to hyperinsulinemia. Brain fog-like symptoms — including lack of focus, concentration and fatigue — are often reported in patients with hyperinsulinemia.
  
  Dyslipidemia is the imbalance of lipids (fats) in the blood; and this typically means that low-density lipoproteins (LDL) or triglycerides are elevated, or high-density lipoproteins (HDL) are too low. Dyslipidemia is diagnosed through routine blood testing, as there are no discernible symptoms. The etiological factors for dyslipidemia are nearly identical to those listed for hyperinsulinemia, and individuals with type 2 diabetes are at an increased risk. There is no direct link with brain fog, but dyslipidemia is certainly a factor contributing to metabolic health, and it has been linked to cognitive decline.

Gut health

Aside from the above-described symptoms of MetS that can trigger or contribute to brain fog, it is important to mention the link between gut health and brain function. Often referred to as the “second brain,” the gut — in communication with the brain in our skull — plays a key role in overall mental health. The gut and brain are uniquely connected by the gut-brain axis, a bi-directional super-highway that carries signals between them. This might explain physiological phenomena such as “butterflies in your stomach,” in which the emotional and cognitive centers in the brain signal peripheral intestinal functions. Additionally, disruption of the microbial balance in the gut (aka dysbiosis) can negatively impact this communication pathway and contribute to a decline in mental and cognitive health.

Poor diet: Ultra-processed, high-sugar and high-fat foods

“Postprandial (post-meal) brain fog” is also worthy of a mention. When a meal is loaded with ultra-processed, refined foods, blood sugar may spike higher, followed by a crash that can trigger brain fog.

Other brain fog triggers

Food allergies and sensitivities, digestive disorders and autoimmune disorders (such as celiac disease) have also been linked to brain fog.

How to prevent brain fog

It’s a lot easier to do something about brain fog or take measures to prevent it in the first place if you know what the root cause is. Some of the common origins of brain fog have been discussed above, for which relief can possibly be found by switching a medication, learning to manage stress, improving quality of sleep or making changes in diet and exercise. Let’s dive a little deeper, focusing on diet and physical activity as controllable factors that can help minimize brain fog.

Diet

How we feel is directly related to what we do or do not consume. Overall dietary patterns, frequency of eating, specific foods and beverages consumed and nutrient density all set the stage for how the brain works. The following recommendations are important to consider when seeking to mitigate brain fog stemming from impaired metabolic or gut health:

• Keep blood glucose levels stable: The basics here are to minimize ultra-processed, refined, and high-glycemic foods that cause blood glucose to spike and then crash, resulting in brain fog. Focus on eating a wide variety of fiber- and micronutrient-rich vegetables, fruits, and whole grains as well as healthy fats and lean proteins. Bonus: Shifting to this type of eating pattern is also considered anti-inflammatory.
   
• Assess food sensitivities/allergies: Work with your healthcare team to identify and temporarily eliminate foods that seem to trigger an immune or gut-health reaction causing brain fog.
  
  
• Nourish your gut microbiome: Because of the gut-brain connection, maintaining gut health is critical for keeping your head out of the clouds. The trillions of beneficial microorganisms that reside in the gut are known as the gut microbiome. Poor dietary choices can disrupt the finely tuned microbial balance in the gut. Gut microbes thrive on fiber-rich plant foods (prebiotics) like leafy green veggies, berries, beans, nuts, seeds, legumes and whole grains. Foods like these that nourish the gut microbiome are linked to reduced inflammation, enhanced immune tolerance, increased insulin sensitivity — and ultimately less chance for brain fog.
  
  
• A few words on intermittent fasting: Proponents of intermittent fasting (IF) will have you believe that IF is the answer to reductions in body weight, body fat and other metabolic risk factors. Research says otherwise. A 2022 study compared IF to caloric restriction and found no significant differences between the studied groups in measures of body fat, lean body mass, blood glucose levels, sensitivity to insulin, blood lipids or blood pressure. That being said, anecdotal cognitive benefits to IF have been reported.
  
  
• Alcohol and recreational drugs: Alcohol disrupts the body’s use of glucose for fuel and can negatively impact blood glucose levels. Any substance that impacts cognitive processing, like alcohol and many recreational drugs do, can certainly contribute to brain fog.

Physical activity

Exercise, or even any physical movement, can help reduce cognitive decline and brain fog. As hard as it may seem, if your brain is feeling foggy, do what your body is capable of and keep moving — as research has shown that physical activity increases cerebral blood flow. Additionally, exercise activates glucose transport independent of insulin, which means you don’t need as much insulin to achieve glucose control. A 2017 review suggests that regular physical activity reduces the risk of type 2 diabetes, insulin resistance and metabolic syndrome. Both the American Diabetes Association and the American Heart Association recommend just 20 minutes per day, and you might be surprised to find out that it's actually quite simple to achieve that goal.

Learn more:
What Is The Best Time To Exercise For Metabolic Health
HIIT vs. Aerobic Workouts for Metabolic Health

Key takeaways

The cognitive fatigue known as brain fog has been scientifically linked to metabolic health. Brain fog can stem from a multitude of causes, including gut dysbiosis and the conditions that qualify an individual for a diagnosis of MetS. Controllable lifestyle and environmental factors that have an impact on brain fog include stress management, getting adequate sleep, consuming a wide variety of healthy whole foods, and committing to a regular exercise routine. A key factor in managing brain fog is keeping blood glucose relatively stable, which can be achieved with both diet and exercise. For those who feel they might need further support in monitoring the impact of diet and exercise on blood glucose, continuous glucose monitors (CGMs) are known to play an increasingly important role.