effects of intermittent fasting on the brain

The Effects of Intermittent Fasting on the Brain

An astonishing amount of 24% US adults have done intermittent fasting at least once. This diet claims to improve your glucose levels, help you lose weight... and now it seems like intermittent fasting can make you smarter! Now the question is, what are the effects of intermittent fasting on the brain?

In this post, we review the effects of intermittent fasting on the brain and cognition. What does intermittent fasting have to say about our brain?

intermittent fasting

Intermittent fasting switches your energy metabolism. During the fasting period, fat is used to produce energy due to a lack of glucose.

Fatty acids are oxidized and converted into ketone bodies, which will be used in replacement of glucose(source)

The three main ketone bodies produced are acetoacetate, acetone, and 3-hydroxybutyrate. During intermittent fasting, the concentration of these ketone bodies will increase.

intermittent fasting and ketone bodies

Types of Intermittent Fasting

There are different ways of doing intermittent fasting. The types of intermittent fasting differ on the length and distribution of the fasting period

Time-Restricted Eating

In this option, you have set fasting and eating periods for a length of one day. The most common setting is the protocol 16:8, in where you can only eat during 8 hours per day.

This ratio will depend on your lifestyle and your preferences. It is healthy and safe to go as low as 14:10 and still get the benefits from intermittent fasting.

The 5:2 Method

In the 5:2 method, you only have 2 days of restricted eating, while the other 5 are a controlled ad libitum .

During the 2 days of fasting, lower the calorie intake to 500 kcal/day and focus on high-protein, and high-fiber foods to keep you filled up.

Alternate Day Fasting

This protocol is similar to the 5:2 method, except the fasting is done every second day.

For those fasting days, drop the calorie intake to 500 kcal or 25% your normal intake. On the normal days, follow a healthy and sustainable diet

The Eat-Stop-Eat

Lastly, the most extreme of these all four types of intermittent fasting. The E-S-E protocol consists on doing full-24h intermittent fasting with no calorie intake at all.

To make it a bit easier, people usually does it from breakfast to breakfast, or from lunch to lunch. Do it only once or twice a week, and go back to a normal and healthy diet on the rest of the days.

types of intermittent fasting

What are the Effects of Intermittent Fasting on the Brain?

Intermittent fasting shows to change your hormonal environment and energy metabolism.

These metabolic changes may enhance brain function by improving your cognitive performance, increasing neuroplasticity, and becoming more resistant to brain injuries and disease (source)

Intermittent Fasting Modulates Brain Hormones

One of the main effects of intermittent fasting on the brain is the increase of hormones and other transmitters that can help you improve your brain function.

Growth Hormone

Only after 6 hours of fasting, your body starts producing more of the so-called Growth Hormone (GH). This hormone favours the utilization of fat over protein for energy production. This will leave room for proteins to build and repair your brain cells.

The growth hormone is also responsible of autophagy, a clean-up and recycling process done to promote health and survival of your cells

Regarding brain function, human growth hormone is implicated in learning and memory, locomotion, psychological behaviors, and neuroprotection (source)

growth hormone meme

Brain Derived Neurotrophic Factor

Brain Derived Neurotrophic Factor (BDNF) is a key molecule involved in the protection of nerve cells and plastic changes related to learning and memory (source)

Intermittent Fasting shows to increase BDNF levels. This increase leads to a higher resistance of your brain cells to dysfunction and degeneration. In other words, Intermittent Fasting and BDNF can protect your brain.

Intermittent Fasting Shifts the Energy Metabolism

Intermittent fasting affects the brain function by shifting your metabolism. It makes ketone bodies the preferred energy susbtrate, and activates mTOR to protect your brain cells.

Increases ketone bodies

The brain only represents 2% of the total body weight, but accounts for 25% of the body’s energy requirement (source). Because of the blood-brain barrier, it’s glucose the main and sole substrate used for energy production in the brain.

In fasting conditions, a metabolic switch occurs. The body shifts from using glucose to fatty acids and ketone bodies (source).

This switch makes the ketone bodies the preferred energy substrate for the brain.

The increase levels of ketone bodies during the fasting period favour the production of BDNF, a neuroprotector and neurostimulator molecule improving learning and memory processes.

intermittent fasting and brain function

Upregulates mTOR

Activity of the pathway mTOR decreases during the fasting period. This leads to autophagy of dysfunctional proteins, which helps removing all ‘useless’ components and protecting the brain.

This autophagy process also deals with oxidative stress, the main cause of aging and cell death (source)

Benefits of Intermittent Fasting on the Brain

As we have seen already, intermittent fasting makes changes in your hormonal environment and energy metabolism. These changes affect the brain, improving cognitive performance, increasing neuroplasticity, and becoming more resistant to brain injuries and disease

Intermittent Fasting improves cognitive performance

Intermittent fasting increases BDNF. The increased levels of BDNF improves learning and memory processes and cognitive function.

Recent research and clinical trials suggest that sustained fasting regimens maintained over months or even years may also improve memory along with executive function, and overall cognition (source)

intermittent fasting improves cognitive performance

Intermittent Fasting Protects the Brain

When doing intermittent fasting, ketone bodies become the main energy source for your brain.

When this ketosis is prolonged for 24h, intermittent fasting confers neuroprotection, maintains cognitive function, and improves mitochondrial function (source)

The regulation of mTOR favours autophagy, which gets rid of the unwanted and dysfunctional molecules, and deals with oxidative stress and cell death.

Thus, mTOR when fasting can also help protect nerve cells and the brain (source)

intermittent fasting protects the brain


Intermittent fasting is a protocol that alternates between fasting and eating periods. Depending on the type of intermittent fasting, the length of these periods will differ.

In this post we have reviewed the effect of intermittent fasting on the brain. To date, it is known that intermittent fasting affects the brain by triggering a metabolic switch and favouring the production of hormones related to brain function and cognitive performance.

Intermittent fasting can help you improve your cognitive performance, learning and long-term memory, and to protect your brain from injury and diseases.

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