Written by Dr. Inez Van Roy on
March 1, 2022
Reading Time: 5 minutes

Medically Reviewed by our Medical Affairs Team

Written by Dr. Inez Van Roy on:

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Keto, does it help or hurt brain fog? The keto diet is famous for supporting weight loss. Others also report better concentration and focus.

However, you might be the unlucky fellow who feels weak and tired after starting this diet. Brain fog on keto is possible, some refer to this as the “keto flu”.

What is keto brain fog? What are the causes and how can we solve them? Keep reading to find out.

What exactly is keto brain fog? 

Everyone and their grandmother seem to get miraculous effects from a keto diet. If you don’t feel those effects, it might be disappointing. You are not the only one experiencing negative symptoms due to the low-carb diet.

Australian researchers found that keto brain fog is a common topic in the media and online keto forums. About one-third of the users of a keto forum felt mental clarity or brain health issues due to ketogenic diets.

What are keto brain fog symptoms?

Some symptoms you might experience are: 

  • Headache
  • stomach or gastrointestinal pain or discomfort
  • diarrhea or constipation or nausea
  • muscle cramps or weakness
  • Cognitive function issues: difficulty concentrating or brain fog
  • flu
  • mental fatigue or feeling faint or decreased energy or dizziness
  • heartbeat alterations
  • sore throat
  • decreased appetite
  • shaking
  • or body aches.

Other words that might refer to these symptoms are “keto-induction” or “keto-adaptation”. If your symptoms are severe, please consult a medic for more information. 

What causes brain fog on a keto diet? 

Why do many feel so weak while pursuing a ketogenic diet? To understand this, we should explain what a keto diet entails. 

A keto diet is a very low-carb, high-fat diet. To obtain ketosis, only 5 to 10% of your caloric intake should be carbs.

In a 2000 kcal calories diet, that looks like 100-200 kcal or 20 to 50 grams of carbohydrates. Day to day that would be half a bun, or one potato (or a bit more if you accept the 10%).

If you want to maintain ketosis, you will have to read the labels. It requires a lot of research on what you are eating as many foods contain carbohydrates. 

Carbs are usually the main provider of energy for the brain (and our body). We eat sugars or carbs and tend to feel energized. Scraping this direct source of energy most likely will come with an adaptation. The results are low insulin levels.

Our body and brain use the glucose and glycogen stored until these are depleted. In other words, the blood sugar levels are dropping. Your body and brain will need to adapt and search for a new source of energy. 

Luckily, our bodies are equipped with a protection mechanism in case of starvation or famine. The human body will access an alternative source of energy when glucose is not available.

A diet full of fats and low in carbohydrates pushes the body in using ketones. This is an energy source derived from fatty acids. As a result of a keto or low-carb diet, you might lose weight really quickly. Our brain will also switch from glucose to ketones if needed. 

Changes in your cognitive function might appear after changing your diet. This might be associated with carbohydrate withdrawal, however recent research is needed.

If you want to start this diet, we highly recommend asking a doctor, or nutritionist for advice. They can provide advice on whether you are a good candidate for this diet, due to your underlying health issues. They can also monitor your health going forward and help you receive the needed nutrients in your keto diet.

Keto seems like a safe diet on a short-term basis. On a long-term basis, there is the risk of your blood sugar dropping too low and causing hypoglycemia.

Isn’t a ketogenic diet good for brain fog?

Keto could potentially have positive effects after the adaptation period. We can’t guarantee these effects as most research is done on animals, and still needs replication.

Still, the positive effects on brain fog seem more obvious for those with pre-existing conditions, f.e. aging, epilepsy, Alzheimer’s disease, or ALS (Lou Gehrig’s disease). There seems to be a ceiling effect for healthy adults, they might not experience the expected effects.

This might be because ketosis supports the mitochondria in the brain. These are the powerhouses that protect us from oxidative stress.

Ketone bodies are produced and used during ketosis. They supply the mitochondria with a special kind of fuel that keeps them in great shape.

For the elderly, ketone bodies are providing the energy needed in their prefrontal cortex and hippocampus. As they age, they seem to show a reduced capacity to use glucose. Eating keto could bypass this issue by providing an alternate source of energy. 

Remedies for Brain Fog on a Low Carb Diet

There is more research needed to suggest a complete remedy for keto brain fog. Drinking enough water and taking care of your health are usually recommended for those who suffer from brain fog. 

Supplementation with MCTs (medium-chain triglycerides) is suggested to improve the time to reach full ketosis. Medium-chain triglycerides might reduce the adverse effects.

Australian researchers found possible beneficial effects of the supplements on keto induction symptoms. They could not confirm whether it improved mood or time to nutritional ketosis (NK). While this is positive news, a review does remark that proof is still very limited.

More research is needed to confirm the effectiveness of these supplements on brain fog related to ketogenic diets.

How long does the keto-flu last?

Keto-related flu is not a recognized disease or diagnosis. It is a group of (flu-like) symptoms experienced after changing to a very low-carb diet. Early researchers referred to it as “keto-induction” or “keto-adaptation.”

The symptoms start the first few days after eating keto. You might feel the worst after a week, and after that the symptoms will diminish in the coming month. 

If you don’t see progress in your symptoms, it might be time to reconsider the diet. A specialist can help you create a keto meal plan to avoid negative consequences. An unbalanced keto diet could have negative effects on cognition, such as

  • impaired brain growth, 
  • a deficiency in spatial learning, 
  • and impaired memory function. 

Professionals can prevent the risk of a lack of micronutrients

Does keto starve your brain? 

While the brain is mainly using glucose as an energy source, it will use ketones when needed on a keto or low carb diet. Neurodegeneration could happen due to oxidative stress. An energized brain will repair damage when needed.

Ketones seem to provide a protective mechanism in case of starvation or fasting. Brain function can be maintained due to this mechanism. This mechanism provides ketones as an alternative to glucose. It spares the available glucose and has more neuroprotective roles

Concluding Thoughts 

Eating low carb or keto diet is mainly used for rapid weight loss. People could experience brain fog or other cognitive symptoms in the first weeks due to this low-carb diet.

After this induction period, the cognitive impairment should clear up. Other symptoms in this adaptation period might look like the flu. 

People who want to try the keto diet should also include more healthy fats and protein so as not to starve themselves. A doctor can give more advice on how to transition. 

Keto can have positive and negative effects. It is important to note that this eating pattern is not easy to maintain as it is restricting.

If you want to learn more about brain fog, then visit our blog by clicking here. If brain fog is getting you down and you would like support in a safe space, you can join our community here

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