Fasting was an evolutionarily advantageous trait for our ancestors. Humans whose brains and bodies could go without food for prolonged periods of time and still function well were more likely to survive and reproduce. Our Greek forefathers, including Plato, Hippocrates, and Aristotle, abstained from food and heralded its rejuvenating effects. Throughout history, in some cultures and religions, it has been customary to fast at certain times during the year. Today, the practice is enjoying newfound popularity among different cultures and generations as science confirms its many health benefits.
While there are numerous advantages of fasting, it is especially good for your brain. Below, I’ll explain how fasting affects fat metabolism and ketogenesis, synaptic plasticity, mitochondrial health, neurogenesis, and how these, in turn, influence brain function. Today the most popular type of fast is intermittent fasting (IF), which involves short-term abstention from food, usually from 12 to 24 hrs.
The Brain Benefits of Intermittent Fasting
Fasting Promotes Ketogenesis
In your body, fat is composed of molecules called lipids which are vital to brain and hormone function and cellular health. A lipid is a molecule made up of a long chain of carbon atoms that are broken off and turned into energy during fat-burning, called lipid metabolism. You can think of it like links on a chain that are broken off at the end one by one and transformed into energy. While the end product is energy, the chemical intermediate step in lipid metabolism is the production of a class of molecules called ketones.
Normally, your body turns carbohydrates from your last meal into glucose for easy energy. When fasting, with no new energy sources entering the body, it resorts to breaking down fat for fuel. This is called ketogenesis and is beneficial for several reasons. Your body burning fat from reserves means a slimmer, lighter you. Also, the ketones produced during the fat-burning process easily cross the blood-brain barrier and are optimal brain fuel.
It Increases Synaptic Plasticity
Your brain is neuroplastic. This means it’s changing form and function every day in response to life experiences, emotions, behaviors, and even thoughts. This morphing ability is called neuroplasticity. Both learning and memory are neuroplastic processes in your brain, involving chemical and structural changes. By altering the number or strength of connections between brain cells, information gets written into memory. It’s not really known exactly where or how memory happens, but the most popular candidate site for memory storage is the synapse, the space between neurons, where they communicate.
As we age, it gets harder to remember names, learn new skills, and pick up new hobbies. There is scientific evidence suggesting that this cognitive decline is due to changes in the composition of NMDA receptors at the cell synapses affecting plasticity. Research shows intermittent fasting can counteract these changes and relieve symptoms of cognitive decline.
Fasting Encourages Neurogenesis
Neurogenesis is the birth of new brain cells. Until fairly recently, it was believed that you were born with all the neurons you were going to have. However, in the 1990s, neurogenesis was confirmed in the brains of adult humans, other primates, and several species. Neurogenesis occurs primarily in the hippocampus, the part of the brain associated with the formation and retention of memories. Caloric restriction has been linked to improved memory function and increased neurogenesis in mice. Research shows that caloric restriction creates a mild stress response in the body, increasing the production of brain-derived neurotrophic factor (BDNF) and new neurons.
More Mitochondria and More Energy
Mitochondria are cellular organelles. They are sometimes referred to as the “powerhouses” of cells because the majority of cellular energy is created in the mitochondria. Since the brain uses more energy than any other part of your body, mitochondria are of critical importance to brain function. Intermittent fasting, especially when paired with exercise has been shown to increase the production of new mitochondria in the brain, a process called mitochondrial biogenesis. For a person, this translates to more efficient energy production and better brain function. Research has also linked mitochondrial biogenesis with increased synapse formation and stability, processes associated with learning and memory retention, respectively.
Fasting Keeps Brain Cells Healthy
Each cell in your body can be considered a separate, individual organism. A community of cells, living peacefully and functioning together in cooperation, yet performing their own specialized function makes up your organs and body. Each separate cell has its own internal parts, called organelles, which carry out particular tasks. For example, mitochondria provide energy. Ribosomes synthesize new proteins, and the nucleus keeps the cell’s DNA safe. Over time, these organelles age, and the cells have to rebuild them. The first step in that process is the destruction of old organelles, called autophagy, which is followed by the creation of new ones.
In the body, most cells undergo renewal on a regular basis. For example, your skin cells keep dividing, and they die and give birth to new cells all the time — even when you’re not injured. After an injury, the skin makes a bunch of new cells and uses them to heal your wound. Yet, nerve cells in your brain, neurons, do not renew themselves. They do not divide at all. As mentioned above, your brain can grow new brain cells through neurogenesis, but only in two places. For the most part, though, your brain cannot replenish dead neurons.
Hence, the ability of brain cells to keep healthy by destroying old organelles and creating new ones is extremely important. The two most common neurodegenerative disorders, Parkinson’s and Alzheimer’s, are associated with brain cells’ inability to destroy old organelles. Science found that fasting for 24 and 48 hours increased cellular autophagy and improved the clearance of old and/or dysfunctional organelles in mice.
Reduces Alzheimer’s Risk and Improves Parkinson’s Symptoms
Fasting and caloric restriction has been shown to help neurological conditions. Age is a major risk factor for both Alzheimer’s and Parkinson’s disease with lifestyle habits, such as exercise and diet also having influence. Ketone production and usage have been shown to mitigate disease progression in Alzheimer’s. Likewise, fasting has proven to have beneficial effects on Parkinson’s disease. The positive effects are amplified by the addition of exercise.
Fasting has been proven to have profound positive effects on optimal brain function and health. It improves the production of new brain cells, enhancing learning and the formation of new memories. It can also help overall brain function through the production of ketone bodies and the generation of new mitochondria. Fasting can be a simple way for anyone to reduce the consequences of aging and risks of neurodegenerative diseases. For six popular plans to practice intermittent fasting see this Healthline article.
Igor Rafalovich is a former neuroscientist with eight years of neuroscience research experience. He is a recipient of the prestigious National Science Foundation Pre-Doctoral Fellowship. As a researcher, he has published papers alongside Nobel laureate Paul Greenguard and developed his interest in translating innovations in science and technology into solutions for health. Igor received a B.S. in biology from the University of South Florida. He is the founder and CEO of GENEius Health. (www.GENEius.me)Share this article!
Interesting article. And I appreciate the facts presented, but fasting isn’t for me. I recently read an article written by a physician who said that making sure you move for 2 minutes every hour and being hydrated (which most aren’t) has an impact on the brain that supports cells and mitigates dementia. so I’m going to stick with that I think!
Excellent article! Thank you for bringing all this research together.
Dan and I began fasting 18ish months ago (Lori started a few months before Dan joined :). We’d been following Dr. Peter Attia and then read a couple of books by Dr. Jason Fung. The combination of the research shared by these doctors kicked us into taking the leap. So far, we believe intermittent fasting has improved our waistlines, our energy levels and our sleeping. So, we’re optimistic this will aid with better aging — time will tell — but so far the research continues to support this.
Thank you for your work!
Thanks Lori and Dan. I recognize you from Twitter. I have been practicing IF for about two years also. I definitely feel like I have more energy, and I just feel lighter most of the day. I do not like to feel “heavy”. I think I would have a bigger waistline if I did not do it, but that is only one reason. I like the idea of healthier telomeres, mitochondria, and brain! 🙂
I have personally loved IF for a long time. Simply cause it just frees you from the what to eat all the time! And also how clean it makes you feel. And it has a lot more benefits, which you have so befittingly shared in this post. We all need to do an IF week a month atleast.
Good for you and your brain, Zeenat. 🙂
I appreciate all this positive information about IF. I think the use of IF is very individual. I tried IF and it didn’t work for me, it raised cortisol levels which I understand can be one impact. My acupuncturists has told me to be sure not to skip breakfast and lunch at the normal hours because that’s when the body is primed to eat, but if you are to use it, to apply IF after lunch.
You make a good point, Sandra. It is not for everyone. You have to do what works for you.