Intermittent Fasting & Cognitive Function
Can Fasting Each Day Boost Your Focus, Memory And Mood?
Intermittent fasting was once an incredibly obscure dieting tactic. Today, it is well-known, widely used, and not particularly shocking.
Thanks to the publication of a number of very popular books such as “The 5:2 Diet”, “Eat. Stop. Fast”, and perhaps most famously, “The Fasting Cure” by Upton Sinclair, intermittent fasting is now a very familiar concept.
The concept was further popularized by the airing of several documentaries on the proponents of fasting. One in particular, shot by the BBC for their Horizon series, brought the idea of intermittent fasting right into the center of public opinion.
In some circles, intermittent fasting is extremely controversial. At least with regards to the online fitness community, its adherents are very vocal about its benefits, while its detractors are scathing about its limitations.
Some say that it causes fat loss without muscle wastage. Others say it is a fast track to reduced performance and slower progress getting faster, stronger, or whatever.
But if you’ve found your way onto this site, you probably don’t care too much whether or not intermittent fasting helps you lose fat or gain muscle or whatever it is that people say it will give you.
You are here because you want to know whether intermittent fasting can improve your mental performance.
You want to know if eating according to an intermittent fasting-style protocol is optimal for cognitive function.
You basically want to know if intermittent fasting can give you the mental edge you need, whether it’s over your colleagues, your competitors, or just over yourself so you can achieve your personal goals more easily.
We’re going to try and answer all of those questions for you.
We’ll talk about what intermittent fasting is (and what it isn’t), what it entails, and how it is usually implemented.
We’ll look at the pros and cons of intermittent fasting from a cognitive performance perspective.
We’ll also look at the potential dangers of intermittent fasting (if there are any that is), and we will touch briefly on the overall effect it has on your health.
If you get to the end of this article and you still have some questions for us, please don’t keep them to yourself. Post any questions or criticisms you may have in the comments section below. We’ll try to get back to you within 48 hours.
What Is Intermittent Fasting?
Before we get into the details of intermittent fasting and its effect on cognition, it is worth us first laying out what intermittent fasting is exactly.
And to do that properly, we need to spell out what it isn’t.
Intermittent fasting is not a diet protocol based on telling you what you can or can’t eat.
It does not have specific macro-nutrient requirements in terms of carbs, protein, or fat limitations.
It doesn’t require you to cut out a certain food group.
Rather, intermittent fasting only places constraints on when you eat.
Or more accurately, it limits the time-frame during which you consume your daily calories.
It’s All About Timing
You do not need to reduce the number of calories you consume per day when intermittent fasting.
You simply need to always consume those calories within a set number of hours window per day. The number of hours per day during which you can eat will hereafter be referred to as your ‘eating window’.
So for example, each day you may choose to consume all of your calories within a 4 hour window. So for the remaining 20 hours of the day, you are fasting.
This eating window is not set in stone.
Some people choose a 7 hour eating window.
Others choose a 1 hour eating window and just eat one meal per day. This doesn’t work for everybody of course, because for lots of people eating enough calories in a single meal is tough. Getting to the point where you can consume no calories for the rest of the day is even tougher.
However, generally speaking, if your eating window is smaller than 8 hours, then you are not intermittent fasting. You are just eating and sleeping like a regular person.
Similarly, if you consume small amounts of calories outside of your eating window, then you aren’t intermittent fasting.
A cup of coffee with a little cream and sugar counts as calories (you’d be surprised how calorific a latte is).
A piece of fruit counts.
It doesn’t matter that it’s “just a little bit”, or that “there aren’t many calories in here”.
It really doesn’t matter; what matters is that you are consuming a biologically significant amount of calories.
When intermittent fasting, you eat in your set eating window.
Outside of that window you consume low calorie drinks like water, green tea, black tea, and black coffee.
Let us give you a few examples just to drive the point home.
Perhaps you are a fairly big, active guy, and you choose a 6 hour window and eat 3,500 calories in that time. A lot of these calories come from carbs, and it includes cheese, beans, nuts, chicken, and leafy green vegetables.
Maybe you are small, lean, and not particularly active. Maybe you choose a 4 hours window and eat 1,800 calories per day. Perhaps a lot of these calories come from fats and protein.
Maybe you are trying to loose weight, and you choose to simply eat a single, very nutritious, hearty, filling, 1,600 calorie meal per day. This meal will probably include lots of fiber, and will usually include some form of lean protein such as tofu or fish.
All of these are fine.
Yes, it would still be intermittent fasting if you ate only fried chicken, beans and waffles during your eating window.
No, that would not be a wise move; you’d still put yourself at risk of heart disease, diabetes, stomach problems, and you wont be getting any fiber or micro-nutrients. You would also be consuming way too much salt.
But fasting doesn’t demand that your diet be conducive to health and longevity. It is simply a timing protocol that you can use wisely or unwisely.
Hopefully you get the idea.
Intermittent fasting doesn’t mean you don’t eat for 23 hours a day then eat a bucket of kale.
It doesn’t mean that you fast for 16 hours per day then eat an extra 1000 calories of fried chicken that you wouldn’t eat otherwise.
It just means you keep everything the same while eating all of your calories in a smaller window than usual.
So if you usually eat 2,600 calories per day, split over 4 meals in a 12 hour eating window, then when intermittent fasting you would consume 2,600 calories in a significantly reduced window in however many meals makes that easy.
That’s that done.
So what are the benefits of intermittent fasting?
Why do people do it?
Why Do People Fast?
People generally fast at regular intervals in order to improve their body composition.
Intermittent fasting, when done correctly, seems to be much more effective for losing fat and preserving muscle than traditional methods of dieting which usually rely on caloric restriction.
How can this be so when the amount of calories aren’t affected?
For starters, there’s the issue of compliance.
Counting calories is difficult. People find it much easier to stay within their caloric limits (or at least not to go over too much) when they have a limited window in which to eat.
You also don’t have to fight the temptation to binge at a BBQ buffet or an ice cream parlor, because you’re fine to do so just as long as this binge falls within your eating window.
But there is also some physical advantages that fasting has over caloric restriction.
First off, fasting for a prolonged period will eventually bring your insulin levels right down. This in turn allows for two other hormones to be secreted into the blood in large quantities: Human Growth Hormone and Hormone Sensitive Lipase.
Hormone sensitive lipase is the hormone that allows you to tap your fat stores for energy. So when your energy levels start to decline, HSL would be the trigger which tells your body you need to start raiding your energy stores. This is the hormone people really want on their side if they are interested in losing fat (and not necessarily losing muscle).
The problem is that HSL is sensitive to insulin.
The presence of insulin in the blood from a previous meal will prevent HSL from being released. You therefore can’t access your fat stores for energy, and you will need to either eat something or you’ll find yourself getting weaker and weaker.
This is the worst side effect of caloric restriction for those of you who care about muscle mass; you just get more tired and your strength plummets as your diet down.
So in order to let HSL do its job, you need to bring insulin levels down to practically 0. And to do that, you need to not eat anything containing glucose molecules or too much protein for 10-12 hours. The easiest way to do that is to just not eat for at least 12 hours.
Once you hit that point, your glucose stores will be depleted and you will actually start to get into the fat stores that bother you so much!
Human Growth Hormone is just as important for fat loss.
HGH does a number of things. As the name suggests, it is an anabolic hormone, conducive to tissue growth. It also releases enormous amounts of fatty acids into the blood. High levels of HGH means that there will be a constant flow of fatty acids into the blood from your fat stores, meaning that your muscle mass will be spared and your fat stores will steadily decline.
Again, HGH is hampered by insulin.
Our HGH levels are highest at night while we sleep. This is because this is usually been the longest since we’ve eaten. However, if you have eaten a high glucose meal shortly before bed, then your HGH secretion will be severely disrupted. This means you wont be able to reap all the benefits of HGH.
When you combine this enhanced secretion of anabolic hormones with a macro-nutrient intake conducive to muscle preservation and physical performance, you have a recipe for serious body re-composition.
However, that is of course not the only reason that people intermittently fast. Many people adopt a fasting protocol in order to improve their overall health and longevity.
Let’s take a look at how intermittent fasting can benefit your health and potentially (according to some) increase lifespan.
Health Benefits Of Intermittent Fasting
There are a number of well-established, robustly proven health benefits to intermittent fasting, as well as to fasting in general. However, we will be focusing on intermittent fasting here. If you are interested in learning about prolonged fasting, then check back soon as we will probably write a full article on prolonged fasting and mental function.
We’ll simply state a few of the health benefits associated with intermittent fasting and cite a study or two to back up these claims.
This study, published in Cell Metabolism in 2014, concluded that “fasting has the potential to delay aging and help prevent and treat diseases while minimizing the side effects caused by chronic dietary interventions.”
Intermittent fasting is know to reduce bodily inflammation. This study looked at Ramadan induced fasting and how it affected otherwise healthy individuals. It found that “These results indicate that RIF attenuates inflammatory status of the body by suppressing proinflammatory cytokine expression and decreasing body fat and circulating levels of leukocytes”.
Intermittent fasting is thought to promote cell regeneration, protect stem cells, and reverse immuno-suppression. This study look at how a diet that mimics fasting was able to reduce IGF-1 signalling, which in turn seemed to have a profound effect on the body’s ability to generate new blood cells.
In a similar vein, a fasting-like diet (short-term fasts) is thought to supercharge the immune system and prime it to fight serious conditions which, according to some, includes cancer. A study (summary discussed here) published in the journal Cancer Cell in July 2016 found that a fasting-like diet in conjunction with chemotherapy was able to remove the “shield” that protects cancer cells from the immune system.
This article looks at the effects of a fasting like diet on a range of risk factors for things like cardiovascular disease, life span, and overall health. It found that “three FMD cycles decreased risk factors/biomarkers for aging, diabetes, cardiovascular disease, and cancer without major adverse effects, providing support for the use of FMDs to promote healthspan.”
Of course, there is a big caveat which needs to be raised here.
While there is an abundance of literature on fasting and its effects on human health and well-being, systematic reviews of this literature have noted weaknesses. As this literature review states, “the few randomized controlled trials and observational clinical outcomes studies support the existence of a health benefit from fasting, substantial further research in humans is needed before the use of fasting as a health intervention can be recommended.”
Now that we’ve looked at the physical and aesthetic benefits of intermittent fasting, let’s get to what you’ve all been waiting for (and what many of you will have skipped directly to): how intermittent fasting can benefit your cognitive function.
Intermittent Fasting & Cognitive Function
Intermittent fasting seems to benefit cognitive function in a number of different but complimentary ways.
For starters, there’s the incredibly powerful physical effect it has on the brain.
Most people have no idea what a profound physical effect intermittent fasting has on the brain. This goes well beyond the kind of benefits you get from some nootropic substances. Here we are talking about deep, lasting, fundamental improvements in the brain’s physical architecture.
This translates into real, observable improvements in memory function.
Let us explain.
Intermittent Fasting & BDNF
Fasting, as we know, causes a rapid elevation in several anabolic hormone blood serum levels.
Well, what a lot of people don’t know is that intermittent fasting also causes a dramatic rise in brain-derived neurotrophic factor, or BDNF for short.
This is not a tenuous link; that intermittent fasting causes an increase in BDNF is a well-established mechanism, observed now in numerous clinical trials.
BDNF is a neurotrophin; a class of chemical which controls neurogenesis (the growth of new brain tissue).
BDNF essentially promotes the proper maintenance, regeneration, and growth of neural tissue. Having healthy levels of BDNF is a sure-fire way to ensure that your brain is optimized for long-term performance. We cannot overstate this: the effect that BDNF has on the brain is immense.
It protects neurons in the brain from degeneration (ref).
It enhances synaptogenesis, which as you will see from the cited study, has a direct effect on memory function.
It directly causes dendrite growth in the brain. Dendrites are a branches section of a nerve cell. They are the communication channels between synapses in the brain.
Obviously, these benefits translate into real cognitive enhancements.
As well as protecting and enhancing your neurons, BDNF has a number of other beneficial effects in the human body. These include, but are not limited to, acting as a natural anti-depressant (ref), improving insulin resistance (ref), and improving quality of sleep (ref).
It is increasingly being investigated for its links to diseases like Parkinson’s disease, Alzheimer’s disease, and Huntington’s disease (ref).
In fact, one study looked at intermittent fasting itself and found that it can improve survival after a myocardial ischemia because it influences BDNF.
So why does fasting boost BDNF?
Well, many think that it is a response to cellular stress. This makes intuitive sense; if your body has no fuel coming in, it makes sense for it to focus on enhancing what it currently has.
Some believe that it is a function of being leaner.
We are far from certain on the exact mechanism in action here.
One thing that we do know is that the link between intermittent fasting and BDNF is a strong one, and that the link between healthy BDNF levels and optimal cognitive function is also a strong one.
That’s good enough for us.
Reduced Oxidative Damage
Intermittent fasting is also known to help reduce oxidative damage.
There is a growing body of work on this relationship, and the results just continue to deepen our interest in intermittent fasting and its potential benefits for long-term brain health.
This trial looked at the effects of alternate day caloric restriction (often practiced as the 5:2 IF technique) on a range of bio-markers in human beings. It found that following an alternate day caloric restriction diet led to a significant reduction in oxidative stress, as well as improvements in a number of other areas.
The researchers concluded: “The improved clinical findings were associated with decreased levels of serum cholesterol and triglycerides, striking reductions in markers of oxidative stress (8-isoprostane, nitrotyrosine, protein carbonyls, and 4-hydroxynonenal adducts)”.
That’s pretty conclusive stuff.
Why is this beneficial?
Well, oxidative damage is in large part what causes DNA degredation over time. This may well be one of the main drivers behind cognitive decline.
Of course, it is not possible to completely avoid age-related cognitive decline.
Ageing is inevitable; we all know that.
But preventing oxidative stress as far as possible is thought to be a reliable way to stay on top of your game mentally for as long as possible. It is also a good way to stay as healthy as possible for as long as possible; oxidative damage is not just something which affects the brain.
Focus & Energy
Fasting, even for as little as 16 hours per day (including 8 hours of sleeping), can be a good way to prevent energy crashes and sustain focus for longer.
This is linked to the benefits of fasting listed above which relate to better blood glucose regulation and enhanced fat loss.
When you eat pretty much anything, insulin is released.
When you have insulin in your blood, you cannot access your fat stores for energy because the hormone that lets you do that, Hormone Sensitive Lipase, is sensitive to insulin.
So when your glucose levels are depleted, your energy levels will start to flatline and you will need to eat something pretty fast in order to keep going.
You will still have insulin in your blood, so you wont be able to access your fat stores for energy; it’ll be either a trip to the vending machine or you will have to fight through some serious hunger cravings and a total energy crash.
Intermittent fasting will place you in a position to be able to access your fat stores for energy, while putting you in a place where for several hours of the day you will have unbroken focus and mental energy.
As you follow an intermittent fasting protocol for longer, you will find that these energy crashes become fewer and further between.
The final benefit of intermittent fasting with regards to cognitive function is purely practical in nature.
At the risk of sounding a little silly, the time-saving aspect of intermittent fasting is perhaps the most immediate and noticeable benefit anybody gets from commencing this eating protocol.
If you reduce the amount of time each day during which you eat, then you drastically simplify your day. You no longer spend a lot of time cooking, fitting in time for meals, wondering what you are going to eat, and so on.
If you only eat during a 6 hour window, for example, then you probably only have time for 2 large meals.
That makes for a very simple, straightforward, manageable meal-prep.
If we’re talking about practicalities, we also need to talk about ghrelin.
Ghrelin, or growth hormone releasing peptide, is the signal to your brain that you are hungry.
The release of ghrelin is what keeps many people from intermittent fasting; they just get too hungry if they don’t eat first thing in the morning and an hour or so before sleep.
However, it seems that ghrelin is more cyclical than responsive.
That is, it seems to peak at certain times rather than in response to hunger.
Ghrelin seems to rise around the time you normally have breakfast. But if you don’t eat, it isn’t the case that more and more ghrelin gets released. Instead, ghrelin levels return to baseline and then peak again later in the day (around lunchtime).
Fascinatingly, if you perform a prolonged fast, then you will find that your ghrelin levels gradually decrease each day.
As you can see from the above graph, each day ghrelin peaks around the same times, but then falls again. Each day the peak level is lower.
This basically means that fasting regularly (or irregularly but for prolonged periods – always to be done under medical supervision) helps lower your ghrelin levels. This in turn will make you more in control of your eating, and less of a slave to hunger pangs.
Health Risks Of Intermittent Fasting
Now that we have covered the potential benefits of intermittent fasting, we need to cover some of the downsides and the risks.
Because make no mistake about it: there are absolutely health risks associated with intermittent fasting if it is not carried out properly.
If you are not capable of managing your diet properly, or you are incapable of measuring caloric intake properly, then intermittent fasting might lead to a sudden drop in body weight.
Any kind of rapid weight change is not conducive to good health and happiness (unless of course your current weight can be described as dangerously obese).
Some people will find that they dramatically under-estimate their caloric requirements when they eat just 1 or 2 meals per day.
If you do want to start intermittent fasting, then you need to get a good handle on your caloric requirements before you begin.
This brings us onto the next danger; blood sugar crashes.
We can’t state this clearly enough: if your blood sugar levels fall dangerously low, it is not a joke. If you allow your blood sugar levels to fall dangerously low, you will find yourself feeling light headed and weak, and you are liable to collapse.
This is particularly true if you have any kind of condition which affects your blood pressure, if you have diabetes, or any kind of heart condition. If you have any medical condition which might affect your blood sugar levels or your blood pressure, then you need to exercise great caution when introducing intermittent fasting.
Talk to a doctor before you proceed. To not do so is just irresponsible.
Finally, we come to perhaps the biggest danger of poorly executed intermittent fasting: dehydration.
We get a great deal of water from our food.
You can go without food for a very long time, but you can only go without water for a few hours before you run into serious trouble.
Dehydration is not a mild concern. It is a serious medical emergency.
If you plan on going hours without eating, you need to make sure that you drink plenty of water during that time.
We’ll say that again: if you are going to fast for 16 hours in every 24, then drink water throughout the day.
There is no set ideal water intake; it varies person to person.
So what should you take from this?
There are a number of points we really need to drive home here, if you do intend to implement intermittent fasting that is.
- Drink water throughout the day; have a big bottle on your desk that you can sip at regularly. Do not go prolonged periods without water. Similarly, do not go overboard and start your morning with 4L – drinking too much water is just as dangerous as drinking too little.
- Start intermittent fasting slowly. Do not jump right in to 1 meal per day.
- Begin by gradually narrowing your eating window down to 8 hours. Stay at 8 hours for a number of days; ideally weeks.
- If you handle that fine, then reduce your eating window by another hour while keeping calories the same.
- If you do this, then increase water intake slightly to accommodate.
- Again, do not increase water intake dramatically. Do so sensibly, following the advice of your doctor.
Is Intermittent Fasting Right For You?
The answer to this question depends entirely upon you.
We have largely covered the benefits to intermittent fasting in this article.
Yet that does not mean that intermittent fasting is overwhelmingly a positive choice for every individual.
We have just tried to highlight the potential benefits because the fact that it may not work for everyone is, in our opinion, self-evident.
The fact that many people might not need any of the benefits listed here is also self-evident. If you have other ways of optimizing your cognitive function and you just love eating regularly, then you have already decided that you don’t need intermittent fasting.
The benefits of intermittent fasting can indeed be achieved by other methods.
If you are bad with diets, you don’t deal with hunger very well, or you have any of the pre-existing health conditions mentioned above, then this isn’t the path for you.
If you aren’t good at controlling your water intake very well, then again this isn’t the route you should take to cognitive enhancement.
But if you have some experience with fasting, you are great at judging your caloric and water requirements, you know you can deal with hunger well, and you are totally healthy, then you might benefit from intermittent fasting.
If you think you stand to benefit from fasting, then we strongly recommend that you book an appointment (or even a phone call) with your doctor and get their opinion. Once you’ve spoken to them and you want to try it out, start slow and progress slowly.
Remember to walk before you can run, and there is no need to jump in at the deep end. Take on what you can handle and you will get better results (and stay healthy).
Henry is a long-time contributor to this site. He has years of experience both using natural nootropic supplements, enhancing productivity, and generally making himself a more efficient, effective, healthier person. He mainly writes about natural cognitive enhancement (through diet, behavior, practices, etc).