FASTING AND BRAIN
How fasting helps your brain, cognitive function, increases learning, memory, and alertness.
Comprising about less than 2% of your total body weight, the brain uses roughly 20% of your daily calories. It’s one hungry beast and for a reason.
Keeping the brain energized and well is one of the main priorities of your body. Without enough higher executive functioning or learning, you would die in dangerous environments and you wouldn’t maintain consciousness.
The growth of our brain has been one of the main drivers of our evolution as a species, skill acquisition, language, memory recall, social co-operation, tool crafting were all facilitated by improved cognition and getting smarter. That’s why you want to provide the brain with the essential nutrients and other foods it needs for thriving. However, there are also many benefits to not eating and depriving yourself of those things with intermittent fasting.
Here are the benefits of fasting on the human brain:
Fasting boosts brainpower by increasing brain-derived neurotrophic factor (BDNF), which helps to grow new brain cells and synapses. It also promotes serotonin, which regulates synaptic plasticity with BDNF.
Even 16:8 style intermittent fasting (we will learn more about different fasting protocols in the following chapters) promotes neuroplasticity and stimulates the production of new brain cells. BDNF also has anti-depressant benefits and it protects against the risk of stroke.
Fasting protects the brain against neurodegeneration.
Fasting in combination with the ketogenic diet is very commonly used to treat epilepsy.
Fasting boosts growth hormone that provides neuroprotection and cell regeneration. Growth hormone not only protects against muscle catabolism (breaking down molecules into smaller units) but also prevents brain cells from dying.
Fasting helps to lose weight, which can improve brain functioning. Studies link a higher BMI (body mass index) with decreased blood flow to regions in the brain that is associated with attention span, reasoning, and higher executive functioning.
Fasting increases mitochondrial biogenesis, which helps to produce more energy. There’s a lot of mitochondria in the brain and other vital organs. More on mitochondria in later chapters.
But there are a lot of people who worry that fasting can cause starvation in the brain. Is it true? Not at all.
To have enough energy a human brain can use about 120 grams of glucose a day and if glucose levels fall below 40mg/dl its functioning begins to suffer. However, during fasting, the brain can get more than enough energy from other sources:
Ketone bodies are derived from fatty acid metabolism and after keto-adaptation, they can cover 50-75% of the brain’s energy demands.
Astrocytes help form the physical structure of the brain and are thought to play a number of active roles, including the secretion or absorption of neural transmitters and maintenance of the blood-brain barrier. They are involved in the physical structuring of the brain. Astrocytes, in other words, regulate the transmission of electrical impulses within the brain.
When fasting, astrocytes in the brain and in the spinal cord can produce ketones that would be used for neuronal metabolism and general functioning.
Ketones are chemicals your liver makes. You produce them when you don’t have enough insulin in your body to turn sugar (or glucose) into energy. You need another source, so your body uses fat instead. Your liver turns this fat into ketones, a type of acid, and sends them into your bloodstream. Your muscles and other tissues can then use them for fuel.
Thus, there’s plenty of energy sources the brain can use while fasting and they all improve your cognitive functioning.
Fasting may help your brain with cognitive decline as well. Autophagy clears out the beta-amyloid plaques that begin to accumulate with cognitive decline and Alzheimer’s progression. Alzheimer’s is also linked to obesity and insulin resistance. One of the main ketone bodies, hydroxybutyrate, actually blocks part of the immune system that regulates inflammatory diseases like arthritis and Alzheimer’s.
Being in a fasted state with higher ketone production sharpens your mind and prevents it from getting dull because of the mild stress response.
Fasting clears brain fog unlike anything else and it will boost your brain performance as well. A lot of people say they experience a heightened sense of awareness, mental clarity, focus, improved attention, and motivation while fasting. This is caused by the rise in BDNF and other neurotrophic factors and hormones that increase your acuities, such as adrenaline, norepinephrine, cortisol, and other endorphins.
Fasted ketosis is one of the most potent and easiest nootropics at your disposal. You can shift your mind into a higher gear of functioning by simply not eating and going into deeper ketosis. Studies have found that a 24-hour fast had no impairing effects on cognition, attention span, reaction time, or memory recall.
The biggest problem that may arise while fasting is hypoglycemia. If your blood sugar levels drop below a safe margin, you will begin to experience shivers, fatigue, forgetfulness, and potentially pass out.
Hypoglycemia is a response to an energy crisis in the brain. Your entire body prioritizes fuel usage for the brain and whenever your blood glucose drops, you’ll become hypoglycemic as to motivate you to find sugar ASAP. Usually, it happens when a person’s blood sugar drops below 60 mg/dl.
You can take juice, hard candy, or glucose tablets. This will usually help your symptoms go away. Check your blood sugar again in 15 minutes and treat every 15 minutes if levels are still low.
FASTING AND IMMUNE SYSTEM
How fasting helps your immune system.
Your immune system is the most important line of defense against the outside world as it helps to deal with foreign intruders, infections, and other environmental stressors.
If you hate being sick, want to have more energy, be healthier, and live longer, then it’s vital to keep your immune system strong.
Fasts that last for 48-120 hours reduce pro-growth signaling and enhance cellular resistance to toxins. They also trigger stem cells, which help to reinvigorate old cells and promote their youthfulness.
One study in particular done by one of the leading researchers of fasting Valter Longo showed that you can reset your immune system by fasting. Mice and chemotherapy patients who didn’t eat for several days saw a significant reduction in white blood cell count. This then turned on signaling pathways for hematopoietic stem cells (HSC), which are responsible for the generation of blood cells and the immune system.
When you starve, the system tries to save energy, and one of the things it can do to save energy is to recycle a lot of the immune cells that are not needed, especially those that may be damaged.
This study shows that extended fasting has a profound impact on the way your body can self-heal itself and strengthen its accord. There are also a lot of potential applications for this, starting with bolstering your immune system against the cold and ending with providing a healthier option for chemotherapy.
“We noticed in both our human work and animal work that the white blood cell count goes down with prolonged fasting. Then when you re-feed, the blood cells come back” – Valter Lango.
While fasting, your body starts mobilizing a lot of its internal fuel sources, such as body fat stores, stem cells, glycogen, and old cellular debris. Some white blood cells also get broken down as a means of throwing away unnecessary material.
Fasting can weaken your immune system only if it becomes an overbearing stressor on your body. It is like any other physiological stressor your immune system has to deal with. If you’re fasting for five days, having intense workouts, not sleeping enough, working long hours, and being stressed out all the time, then, of course, you’re more prone to getting sick.
It’s important to expose yourself to different stressors to make yourself more resilient against them as well. However, you have to start from where your current ability is. As you start practicing more intermittent fasting, your immune system gets stronger and you become less affected by the ebbs and flows of stress.
It’s important to note that fasting boosting your immune system works both as disease treatment as well as prevention. If you want to keep your immune system strong, then you should practice some form of intermittent fasting continuously.
Arguably, you can get a much stronger effect faster by fasting on the ketogenic diet that’s already characterized by lower levels of liver glycogen and insulin.
You won’t be able to have a complete reboot on your immune system or activate autophagy with eating the ketogenic diet throughout the day because high amounts of fat and calories still signal the presence of excess energy in the body. However, you can definitely get into the immune system reset zone much faster with an already depleted glycogen reserve when eating a low carb diet. Combine that with eating one meal a day and you’ll be in mild autophagy even on one-day fasts.
Combining the ketogenic diet with intermittent fasting is likely safe for most people. However, pregnant or breastfeeding women and those with a history of disordered eating should avoid intermittent fasting. People with certain health conditions, such as diabetes or heart disease, should consult with a doctor before trying intermittent fasting on the keto diet.
Though some people may find merging the practices helpful, it’s important to note that it may not work for everyone.
Fasting Mimicking Diet and the Immune System
Valter Longo has also come up with his own way of replicating these benefits with what he calls the Fasting Mimicking Diet (FMD). Here’s how it works:
- You eat about 500-1000 calories every day
- Your daily macros are low protein, moderate carb, moderate fat
- You eat things like a nutbar, a bowl of soup, and some crackers with a few olives or something
Day One: you eat about 1000 calories –10% protein, 55% fat, and 35% carbs
Day 2-5: you eat about 500-700 calories –10% protein, 45% fat, 45% carbs
Day 6: you transition back to a normal caloric intake with complex carbs, vegetables, and minimal meat, fish, and cheese
Studies on the fasting-mimicking diet have shown that it lowers cholesterol, C-reactive protein, blood glucose, IGF-1, and blood pressure. However, it’s possible these effects simply came from the caloric restriction. FMD is often prescribed to elderly people.
To get the full benefits of autophagy and stem cell growth, it is recommended to avoid all calories and fast for a longer time.
Eating very low protein with high carb also causes less satiety, which makes it more difficult to stick to the FMD schedule. You’re much better off by having a longer fast.
Whatever the case may be, you should adopt a fasting focused lifestyle as to promote longevity, youthfulness, and create an antifragile immune system. The next most important thing for that is to take care of your gut because that’s where most of the immune system is located in.
FASTING AND GUT HEALTH
How fasting improves your gut health.
Diet and lifestyle play a huge role in modulating gut microbiota, which has an enormous impact on one’s health and overall lifespan.
Microbial dysbiosis (or microbial imbalances) are associated with increased risk of cardiovascular disease, obesity, metabolic syndrome, cancer, and autoimmune disorders
Different macronutrients and foods reshape the composition of the microbiome and both short term and long term dietary changes can influence microbial profiles. However, not eating and fasting have a profound impact on the gut as well.
Gut homeostasis plays an important role in longevity. Dietary restriction has been shown to prevent gut pathologies and extend lifespan in fruit flies.
It’s been proven that short-term intermittent fasting improves gut health and extends lifespan in fruit flies.
Other studies have shown that intermittent fasting promotes clearance of pathogens and infectious bacteria and helps to heal the gut in mice infected with salmonella.
Fasting protects the gut against the negative effects of stress, such as inflammation. Fasting activates cAMP, which further activates genes that promote intestinal lining integrity and strength. The cognitive benefits of fasting on the brain will also improve your mood and improve stress resiliency which protects against leaky gut.
Intermittent fasting promotes white adipose tissue browning and reduces obesity by shaping the gut microbiome. The gut microbiota influences adipose tissue browning and insulin sensitivity by signaling the browning of white fat into brown fat.
Caloric restriction and weight loss increase the number of beneficial bacteria in the gut called Bacteroidetes. Obese people have less of these bacteria than lean people. Caloric restriction enriches phylotypes in the gut that are positively correlated with an increased lifespan.
Fasting and time-restricted feeding heal the gut by giving your intestines rest from breaking down food. Digestion requires about 25% of the calories from each meal. Being in a fasted state promotes anti-inflammatory cytokines and cellular autophagy that instigate gut healing.
Fasting also increases the activity of the migrating motor complex (MMC), which is a mechanism that controls stomach contractions in a cyclical manner over 2 hour periods. The MMC cleans out the GI tract and helps to eliminate undigested food particles. It’s regulated by feeding/fasting hormones such as ghrelin, serotonin, cortisol, and somatostatin. Eating inhibits MMC and not eating increases it. If you have longer breaks in between meals then you’ll digest and assimilate your food much better and prevent any kind of small intestine bacterial overgrowth or SIBO.
Another study found that time-restricted feeding restored a variety of beneficial strains of bacteria in mice.
Fasting has been shown to also improve symptoms of irritable bowel syndrome (IBS) as well.
A group of researchers from MIT found that fasting for just 24 hours boosted the regeneration of gut stem cells in young as well as old mice. One of the scientists, Omer Yilmaz, said:
“This study provided evidence that fasting induces a metabolic switch in the intestinal stem cells, from utilizing carbohydrates to burning fat.”
Another aspect of it has to do with shifting into ketosis that reduces inflammation and supports healing of the gut.
However, fasting may cause some gut issues if done wrong:
1. Fasting and eating at night may lower your sleep quality. Some species of bacteria like Enterobacter aerogenes are sensitive to melatonin(the sleep hormone), which influence circadian rhythms. A disruption in circadian rhythms can disrupt the microbiome and thus negatively affect metabolic health. That’s why it’s important to not overeat at night. (Refer to bonus chapter at the end of the document for more information on circadian rhythms).
2. Prolonged restrictive diets may cause a lack of microbial diversity. The gut microbiome can respond to changes in the diet very fast and thus restructure the microbiome according to that. Short-term consumption of either fully animal or plant-based diets alters the gut microbial status, which can cause trade-offs in carbohydrate or protein metabolism.
3. Fasting decreases the size of some digestion organs like the small intestine and liver, which can lower the capacity to consume food. That’s why you may find it more difficult to eat as much as you did before when breaking your fast. However, these organs will regrow themselves quite rapidly and they’ll become more functional afterward.
All of these issues are easily solvable and can be fixed by simply adjusting your fasting schedule.
It might seem that, because of not eating, fasting will destroy all the healthy bacteria in your gut and lead to autoimmune disorders in the future. However, this is not the case:
In a study on mice, scientists found that intermittent fasting didn’t wipe out the good bacteria in the gut or destroy their diversity. Instead, intermittent fasting actually improved bacterial diversity. This probably has to do with the life-extension benefits of dietary restriction found across all species. When the bacteria are faced with mild starvation or fasting they live longer and promote energy efficiency through diversity.
Fasting promotes the diversity and dynamics of the microbiome, which is determined by feeding and fasting cycles of the host. At the same time, it will still starve off some of the pathogens, viruses, and bad bacteria.
Time-restricted feeding has been shown to prevent weight gain, improve gut diversity, and circadian cycling of the gut microbiome in mice despite being fed a pro-obesity diet. Mice who were allowed to eat the same diet ad libitum whenever they wanted get obese and sick.
In the 2017 Annual Review of Nutrition, it was said that prolonged intermittent fasting has sustained improvements in health and they may be caused by benefits on circadian biology, the gut microbiome, and better sleeping patterns. Intermittent fasting already has so many health benefits on your metabolism, body composition, cognitive functioning, and longevity but it’s a win-win for your gut microbiome as well.
Part of the reason for taking care of your gut is so important has to do with how the microbiome affects your cognitive functioning. Over 70% of your serotonin –the feel-good hormone –gets produced in the gut and all the other circadian rhythm-related processes are also linked with that.
Science has now discovered that microbial life inside living organisms has played a crucial role in shaping the evolution of the said organism. In fact, the mitochondria are descendants of bacteria that millions of years ago developed a co-existence with our ancestral bodies. This has led to the suggestion of the concept of a Microbe-Gut-Brain (MGB) Axis.
The MGB Axis is this network of biochemical signaling between the gastrointestinal tract (GI) and the central nervous system (CNS). It includes the enteric nervous system (ENS), the endocrine system, the hypothalamic-pituitary axis (HPA), the autonomic nervous system, the vagus nerve, the endocrine system, and the gut microbiome.
Your immune cells, muscle cells, cells of the gastrointestinal tract are all mediators of the neuro-immuno-endocrine system that are influenced by both the brain and the gut microbiome. In fact, it’s been thought that the microbiome plays a much more influential role in the state of your being than the brain.
It’s a complex ecosystem that consists of trillions of microorganisms and bacteria. The ’thing’ you call ’I’ is comprised of this collective consciousness of many living organisms and cells inside your body. Hence the importance of taking care of your gut and mitochondria with fasting.
FASTING AND MITOCHONDRIA
How fasting improves your mitochondrial health.
Mitochondria are known as the powerhouses of the cell. They are organelles that act like a digestive system that takes in nutrients, breaks them down, and creates energy-rich molecules for the cell. The biochemical processes of the cell are known as cellular respiration. Many of the reactions involved in cellular respiration happen in the mitochondria. Mitochondria are the working organelles that keep the cell full of energy.
Mitochondria are small organelles floating free throughout the cell. Some cells have several thousand mitochondria while others have none. Muscle cells need a lot of energy so they have loads of mitochondria. Neurons (cells that transmit nerve impulses) don’t need as many. If a cell feels it is not getting enough energy to survive, more mitochondria can be created. Some- times mitochondria can grow larger or combine with other mitochondria. It all depends on the needs of the cell.
However, mitochondria do much more than just producing energy. They also produce chemicals that your body needs for other purposes, break down waste products so they’re less harmful, and recycle some of those waste products to save energy.
The key to increased mitochondrial biogenesis and longevity is to prime the body towards a fat-burning metabolism. This increases your cells’ ability to produce energy from its own internal resources (autophagy) and lowers insulin levels (less oxidative stress).
Intermittent fasting benefits the mitochondria both ways –in protecting against free radical damage as well as enhancing energy production. But intermittent fasting increases mitochondrial functioning in many other aspects as well.
As you age or when you experience high levels of stress, you become more prone to mitochondrial dysfunction and accelerated aging. Mechanisms mediated by fasting such as increased NAD+, sirtuins, and FOXO proteins make your cells more resilient against environmental stressors and energy depletion.
In nature, animals would have to face high levels of stress only when going through some drastic seasonality or climatic change that would jeopardize their food resources. That inevitably imposes more bouts of fasting on them and thus make them react in a protective manner.
If we were to replicate this response in the contemporary setting, then, as Herman Hesse pointed out:
„the most intelligent thing to do would be to not eat.“
FASTING AND WEIGHT LOSS
How fasting helps accelerate fat loss.
We can all get a bit hungry if it has been hours since we last ate. But spare a thought for how hungry Angus Barbieri (pictured above) must have been after he went 382 days without eating.
That’s not a typo. In 1965, 27-year-old Angus really did fast for one year and 17 days. He ate no food at all and lost 125 kilograms.
Angus was reportedly sick of being obese and checked into the University Department of Medicine at the Royal Infirmary of Dundee weighing 207kg. He told hospital staff he was ready to cut out food altogether, so doctors happily agreed to monitor his progress.
Angus’s doctors didn’t really expect the fast to last long. But they thought a short fast would help him to lose some weight. To compensate for his lack of nutrients, he was prescribed multivitamins to take regularly, including potassium and sodium, as well as yeast.
As days turned to weeks, Angus’s persistence increased. The Scot wanted to reach his reported “ideal weight” of 82kilograms so he kept going, much to his doctors’ surprise.
Angus would attend hospital visits frequently and often stay overnight. He received regular blood tests, all of which revealed his body was, remarkably, functioning just fine.
As weeks turned into months, he compensated for his lack of food by drinking more black tea, black coffee, and sparkling water, of which all are calorie-free. His body began to adapt to the lack of food by burning its own fat stores for energy.
For the last eight months, Angus’s blood glucose levels were consistently very low, around 2 mmol/l (36mg/dl) but the Scot did not suffer any adverse effects as a result. In the final few months, he began to have a pinch of sugar or milk in his tea and coffee.
Angus eventually called it quits after 382 days, having finally reached his dream weight of 180 pounds.
According to a Chicago Tribune report, he had forgotten the taste of food before his first meal after the fast. He ate a boiled egg with a slice of bread and butter for his first breakfast, telling reporters: “I truly enjoyed my egg and I feel very full.”
Five years later, Angus remained at a comfortable weight, weigh- ing 196 pounds.
As this story attests, fasting is also the healthiest and easiest way to reverse obesity.
Contrary to popular belief, intermittent fasting doesn’t slow down the metabolism but actually increases it by 3.6% after the first 48 hours. Even further, 4 days in, resting energy expenditure increases by up to 14%. Instead of slowing down the metabolism, the body revs it up and puts it into a higher gear. This is probably caused by increased adrenaline so that we would have more energy to go out into the savannah and find some food. The scarcer calories become the more detrimental it is to succeed in hunting.
In a fasted state, we actually become more efficient with the food we eat, instead of storing it all. With the lack of calories, especially carbohydrates, we become more insulin-sensitive, meaning that we need less of it to lower our blood sugar levels back to normal. Fasting can actually reverse insulin resistance and reduces overall blood sugar levels.
There’s no reason to be concerned about malnutrition during fasting because our fat stores can deposit almost an infinite amount of calories. The main issue is rather micronutrient deficiencies. Potassium levels may drop slightly, but even 2 months of fasting don’t decrease it below a safe margin. Magnesium, calcium, and phosphorus remain stable because 99% of them are stored in our bones. The man who fasted for 382 days maintained such a lengthy fast with no harmful effects on health thanks to taking a simple multivitamin. That’s all you need to survive for that long.
In fact, one review showed that whole-day fasting could reduce body weight by up to 9% and significantly decrease body fat over 12–24 weeks.
Another review found that intermittent fasting over 3–12 weeks was as effective in inducing weight loss as continuous calorie restriction and decreased body weight and fat mass by up to 8% and 16% respectively.
In addition, fasting was found to be more effective than calorie restriction at increasing fat loss while simultaneously preserving muscle tissue.
FASTING AND GROWTH HORMONES
How fasting boosts human growth hormone production.
HGH is a hormone made by the pituitary gland that plays an important role in the development of children and adolescents. This hormone is indispensable to adults as well, because an HGH deficiency may lead to higher levels of body fat, lower lean body mass, and decreased bone mass. The function of HGH starts by traveling through the bloodstream and getting metabolized in the liver. HGH is then converted into several other growth factors, the most important of which is the insulin-like growth factor.
Studies show that fasting leads to a major increase in HGH levels. One study found that 3 days into a fast, HGH levels increased by over 300%. After 1 week of fasting, they had increased by a massive 1,250%.
Other studies have found similar effects, with double or triple HGH levels after just 2–3 days of fasting.
Multiple methods of intermittent fasting are available. One common approach is a daily 8-hour eating window with a 16-hour fast. Another involves eating only 500–600 calories 2 days per week.
Intermittent fasting can help optimize HGH levels in two main ways. First, it can help you drop body fat, which directly affects HGH production. Second, it’ll keep your insulin levels low for most of the day, as insulin is released when you eat. Research suggests that insulin spikes can disrupt your natural growth hormone production.
One study observed large differences in HGH levels on the fasting day compared with the eating day. Shorter 12–16-hour fasts likely help as well, though more research is needed to compare their effects with full-day fasts.
After 3 days of fasting, HGH increases dramatically in non-obese individuals, but flats out after day 10. In obese people, there is little to no reported rise after fasting from 14 to 38 days. Hypothetically, this happens as a response to preserving lean tissue.
What goes hand in hand with HGH is insulin-like growth factor (IGF-1). It’s one of the major growth factors in mammals which together with insulin is associated with accelerated aging and cancer. Just 5 days of fasting can decrease IGF-1 by 60% and a 5-fold increase in one of its principal IGF-1-inhibiting proteins: IGFBP1.
POTENTIAL SIDE-EFFECTS OF FASTING
There may also be some negative consequences of fasting.
Headaches, dizziness, lightheadedness, fatigue, low blood pressure, and abnormal heart rhythms are all short-term. Some people may experience impaired motor control or forgetfulness. But these are all symptoms of withdrawal, not fasting. Because most people rarely get to use their own body fat for fuel, they become too dependent on glucose. It’s like an addiction that makes them crave more sugar.
When I first starting to practice intermittent fasting some people experience feelings associated with hypoglycemia. It is simply a feeling of lightheadedness whenever one stands up too quickly. After going on a ketogenic diet those signs will disappear completely, any mental hindrance caused by an inner energy crisis will be mitigated. Once the body adapts to utilizing fat for fuel, the brain will accept ketones and will also reduce hunger.
Fasting may cause some flare-ups of certain medical conditions, such as gout, gallstones, or other diseases. This is yet again not because of fasting directly but because of the overall high amounts of toxins in the body. The adipose tissue is more than a caloric pantry. It also stores poisons and infections that we digest. Once you start breaking down triglycerides, those same toxins will be released into your bloodstream again and will get flushed out. That’s why fasting is an effective detox tool, as it cleanses the organism completely.
In comparison to all of the empowering health benefits of fasting, these few side-effects are minute and not guaranteed. They may or may not happen. What’s certain is that they will be alleviated after some time once the body adapts to a new state.
By applying dietary restriction with fasting you will likely gain exponentially more freedom and results. It would be unwise to not take advantage of such an easy yet powerful strategy as simply not eating. Instead of looking for another shortcut or try- ing to find the next magic supplement that will increase your lifespan, you can just stop eating for a while and see how your body reacts.