Healthy &slim with Keto Recipes – Ketogenic Diet Side Effects

If you’re just starting the keto diet, it can be difficult to concentrate. You can’t think straight, you’re forgetful. You don’t have a headache, but it looks like your brain just doesn’t work properly. You’ll probably suffer from brain fog. Brain fog is part of keto flu, although not everyone suffers from it.

Causes of brain fog

There are multiple causes of brain fog. A known cause is a change in hormone levels. Both pregnant women and women in the (pre) menopause can suffer from this.

Certain diseases, such as fibromyalgia, can also lead to brain fog. The cause is probably the pain. Pain affects how the brain functions.

Many other conditions, such as diabetes, intestinal disorders, neurodegenerative disorders, brain damage, allergies, and medical treatments (e.g. chemo therapy) can also lead to brain fog.

And the transition to the keto diet can also lead to brain fog.

Transition from glucose to ketones

Our brains need a lot of energy. On a standard diet, this means that glucose is brought to the brain through the blood and crosses the blood-brain barrier there using GLUT1.

The moment you’re in ketosis, ketones can pass through the blood-brain barrier and fuel your brain.

If you’re just starting the keto diet, it can take several days and sometimes even several weeks for you to get into ketosis. The same applies if you have regular cheat days, you will then go in and out of ketosis. These are the times when you can suffer from brain fog.

You don’t get enough glucose and you don’t create enough ketones to meet the full energy needs of your brain.

Get and stay in ketosis quickly

This is why it’s so important when you’re just starting out with the keto diet, to limit your carbs very strictly and have absolutely no cheat days. This way you give yourself the best chance to get into ketosis quickly.

Once you are able to stay in ketosis, the brain fog will gradually disappear. This is a process. You have used carbohydrates as the main source of energy for years and your brain has therefore used glucose as an energy source for years. Now your body has to switch and this is a very big change.

Eating lots of carbohydrates for years has led to enzymes and the ketolysis process by which your brain can use ketones being more or less put on hold. So you have to start activating this again and your body has to start creating new pathways. Your metabolism is going to change completely again (again, because as a baby you could do this just fine, babies are born in ketosis). So such a process takes time.

What’s more, it’s not just about getting into ketosis quickly, but also staying in ketosis. You need long-term high concentrations of ketones to make it easier for the ketones to cross the blood-brain barrier to fuel the brain.

The moment you become fat-adapted, you will even start to notice that ketones are a very pure fuel for your brain and your brain is actually starting to function better. So you can think much more clearly, concentrate better, etc. This is a really special sensation.


Another reason for brain fog during the switch to the keto diet may be dehydration. One of the reasons you sometimes lose a lot of weight in the first week of the keto diet is because you lose a lot of fluids. This is especially the case if you switch very suddenly from a diet high in carbohydrates to the keto diet.

A diet high in carbohydrates ensures that you retain a lot of moisture in 2 ways. First, store energy that you don’t need directly as glycogen in your muscles and liver. Glycogen is stored with moisture. So as soon as you start burning glycogen, this moisture is released. So you’re going to pee more.

Secondly, your body makes a lot of insulin if you eat a lot of carbohydrates. Insulin causes your kidneys to retain fluid and sodium. The moment your insulin level is low, you start to urinate this fluid (with sodium). This is why it’s so important that you use some extra salt (sodium), but also potassium (avocados) and magnesium to make sure you don’t get keto flu. And it is therefore also important to drink enough. Sufficient but not excessive, because the more you drink, the more you pee and therefore the greater the imbalance between the electrolytes can become.

If you drink too little and pee a lot, you can also get brain fog. Dehydration can also cause your blood pressure to get too low.

MCT oil and exogenous ketones

You may be wondering if you can get and stay in ketosis faster by taking MCT oil and/or exogenous ketones. Indeed, there is some evidence that MCT oil can help you get into ketosis faster and potentially stay in ketosis more easily. You can read more about this here.

There is also evidence that exogenous ketones in the form of esters, such as those used in the medical keto diet, can cause the patient to be quickly put into ketosis and kept well in ketosis. Recently, consumers have also been able to buy ketonesters. They are very expensive and very dirty (I didn’t try them myself, but heard this say). There’s only one company that makes and sells ketonesters to the consumer and that’s HVMN. They also sell all kinds of other products, but only for the ketonesters there is also real proof that they work.

There’s no evidence that ketone salts work. Of course, this doesn’t mean you can’t try, but it’s probably wasted money.

It is important to realize that there is a big difference between endogenous ketones, so ketones that your liver makes and exogenous ketones, ketones pills and drinks. If you want to lose weight, then you want to burn your body fat, you only do this via endogenous ketones. It is best to think of exogenous ketones as very quickly available energy. But if you want to lose weight, you want less energy from the outside and start consuming your own energy supply (body fat).

The reason ketonesters are very useful in the medical world is that the goal in these patients is to treat brain disorders, such as epilepsy, and the goal is not to make them lose weight.

Transition is tricky, but ketosis has many benefits

The moment you are completely fat-adapted, you will notice that you can think much better, concentrate better, solve problems better. But ketosis has many more benefits. We now know that ketosis can reduce oxidative stress in the brain, give your neurons more energy and stimulate neurotransmitters. This greatly benefits your mental health.

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