The ketogenic diet, or "keto" diet, has gained popularity as a weight loss strategy, with approximately 40% of Americans making New Year’s resolutions to lose weight. While it can be effective, it's crucial to understand its potential effects on the body, including the possibility of experiencing brain fog. This article explores the relationship between the ketogenic diet and brain fog, its causes, and possible solutions, drawing on research and expert opinions. As with any drastic diet change, it's always recommended to consult with a primary care physician before starting.
Understanding the Ketogenic Diet
A ketogenic diet is a low-carbohydrate, high-fat diet that forces the body to burn fat for energy instead of carbohydrates. The original ketogenic diet derived 70-75% of all calories from fat, 20-25% of calories from protein and 5-10% from carbohydrates. When you eat a diet high in carbohydrates, your insulin levels rise after you eat, but then quickly fall. This decrease in insulin alerts the hunger center of your brain to provide more food.
Russell H. Swerdlow explained, "Now we use a looser definition of a ketogenic diet as any diet that raises the levels of ketone bodies in the blood.” Those ketone bodies then can be measured in the blood to see if ketosis -the act of the body burning up fat instead of carbs -has been achieved.
What is Brain Fog?
Brain fog is not a medically defined term, but rather a descriptive term used to describe a range of cognitive symptoms. Brain fog is synonymous with mild cognitive impairment. When you have brain fog, you aren’t quite yourself.
Depending on the situation, it might mean:
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- Difficulty concentrating or focusing
- Forgetfulness
- Feeling cloudy
- Feeling slow or “off”
- Not being able to think clearly
- All of the above
Having brain fog can decrease your productivity, communication skills, and mood. Others will notice.
The Link Between Keto and Brain Fog
People adopt keto and low-carb diets for a wide variety of reasons, but one of the biggies is improved cognition. That’s why it can be really frustrating to have brain fog on keto. Isn’t the keto diet supposed to fix brain fog? Speaking for myself, I’m at my best mentally when in ketosis. I’m focused, I think more clearly, and can concentrate for longer.
While many individuals experience improved mental clarity on a ketogenic diet, some report brain fog, especially during the initial stages. This phenomenon can be attributed to several factors, including the body's adaptation to using ketones as its primary fuel source and potential electrolyte imbalances. However, keto-related brain fog is just one blip in the brain fog universe. If you’re experiencing brain fog on keto, it might have nothing to do with keto. It might be a lack of sleep, a lack of exercise, a nutritional deficiency, or a health condition.
Adaptation Period
Brain fog is one of several symptoms that often affect people in the early stages of low-carb dieting, as well as headaches, irritability, low energy, insomnia, constipation, and weakness. The soft hunk of gray matter is only 2% of your bodyweight but demands 20-25% of your fuel. It’s greedy. Glucose is your default brain fuel. When glucose is available, the brain runs almost entirely on this simple sugar.
When starting a keto diet, the brain needs time to adapt to using ketones instead of glucose for fuel. This transition period can lead to temporary cognitive difficulties. The brain doesn’t like that. It has less energy. On a keto diet, your liver burns fat to produce ketones. When ketones are elevated (called ketosis), your brain runs primarily on ketones instead of glucose. Ketones are your backup brain fuel.
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But the shift from glucose to ketones doesn’t happen instantly. It could take a day, or it could take a week or more. In general, higher-carb starting points will require a longer transition period. As a result, glucose supply to the brain dips.
Electrolyte Imbalance
When you restrict carbs, insulin (your master energy hormone) stays low. Sodium intake is. That’s because a whole food keto diet is naturally low in salt. (Salt is 40% sodium). You may experience multiple days of headache, fatigue and constipation a few weeks into the keto diet, which can be attributed at least in part to the body losing water.
Electrolytes are often lost because of the rapid reduction in your body’s water content. Be sure to get plenty of electrolytes, especially sodium and potassium. Take them along with fluids to replace what’s lost on keto.
Other Potential Causes
The symptom of brain fog is associated with many health conditions. These include:
- Head injury
- Fibromyalgia
- Diabetes
- Allergies
- Gut dysbiosis (SIBO or candida)
By restricting the favorite food of bad microbes (carbs), the keto diet may help with both SIBO and SIFO. Keto is supposed to improve cognitive function, not put you in a fog.
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Alleviating Brain Fog on Keto
Fortunately, brain fog experienced on a ketogenic diet is often temporary and manageable.
- Time: A week or so of keto dieting and the brain fog should resolve. If you’re foggy during your first week of keto, don’t panic. It’s normal, and probably will resolve naturally within a few days.
- Hydration and Electrolytes: It’s important to stay hydrated and maintain adequate electrolyte levels, especially sodium, potassium, and magnesium. Electrolytes are often lost because of the rapid reduction in your body’s water content.
- Sufficient Rest: Many of the symptoms can be alleviated with water, rest and time. Maybe you simply need more sleep, more exercise, or more clarity on a health condition.
- Meeting with a Dietitian: Sullivan suggests meeting with a dietitian to understand how much fat intake is needed and what kinds of fats should be consumed.
Potential Benefits of Ketosis for Cognitive Function
Transition period aside, being in ketosis has been shown to have cognitive benefits. And of all the keto flu symptoms, brain fog may be the most vexing.
Since the 1930s, experts have known that ketogenic diets affect how the brain works. Ketones are an extremely potent fuel source for your brain. They have even been tested in a medical setting to treat brain diseases and conditions such as concussion and memory loss. Eliminating carbs can also help control and stabilize blood sugar levels. This may further increase focus and improve brain function.
In numerous physiological states, including the neonatal period, fasting, calorie restriction, starvation, post exercise, and very low carbohydrate diets, the body is able to generate ketone bodies (acetoacetate and beta hydroxybutyrate) as an alternative brain energy source to glucose. In long-term fasting, ketone bodies can supply >60% of the brain’s energy requirements, and are actually preferentially taken up by the brain over glucose when adequate amounts of both energy substrates are available, although glucose will always be used in conjunction with ketone bodies.
Keto for Long-COVID
COVID-19 infection causes cognitive changes in the acute phase, but also after apparent recovery. Over fifty post (long)-COVID symptoms are described, including cognitive dysfunction (“brain fog”) precluding return to pre-COVID level of function, with rates twice as high in females. This cognitive dysfunction is associated with impaired cerebral glucose metabolism.
Ketone bodies improve brain energy metabolism in the face of cerebral glucose hypometabolism in other conditions [mild cognitive impairment (MCI) and AD]. Medium chain triglyceride (MCT) is an exogenous route to nutritional ketosis and may mitigate cerebral glucose hypometabolism associated with post COVID-19 infection.
Considerations and Precautions
While the ketogenic diet may offer cognitive benefits for some, it's not suitable for everyone. The keto diet should be avoided if you have certain medical conditions, including pancreatitis, liver failure, fat metabolism disorders and others.
Too much of the wrong kind of fat can negatively affect the heart and the cardiovascular system. It's crucial to ensure adequate and healthy fat intake. Sullivan suggests meeting with a dietitian to understand how much fat intake is needed and what kinds of fats should be consumed. “On keto, we are increasing the amount of fat in someone’s diet, but we need to make sure it’s a healthier type of fat.”
It's also essential to differentiate between ketosis and ketoacidosis. The latter is a very serious condition that can affect people with diabetes.