I’ve personally been implementing and experimenting with fasting for close to a year now. Observing numerous benefits to both my body and cognition, I’ve since become a big proponent. I strongly believe that most people should be practicing fasting in some form or another — the evolutionary biological rationale for fasting coupled with the proven health benefits are just too compelling to ignore.
I’ll take the time to flag that I am not a doctor and that you should consult with a medical practitioner before commencing a fasting regime. The following information has been derived from my own personal experiences, experimentation and research.
Fasting is typically achieved by ingesting no or minimal amounts of food and caloric drinks for periods that typically range from 12 hours to three weeks. If approached correctly and for the right reasons, it can become an easily adaptable component of your lifestyle. Fasting doesn’t require a lot of thought, nor does it entail the dietary restrictiveness advanced by the majority of contemporary diets. By simply restricting the period that you eat within during each day, it can be both easy and convenient to implement.
Fasting is not however, is a ‘be all and end all’ cure for the negative symptoms of a life lived in contemporary society — such as our 24/7 access to abundant and calorie dense foods. It should instead be viewed as a component of a balanced and healthy lifestyle — i.e. one that incorporates sound nutrition, adequate exercise and high quality sleep.
With this in mind, I’ll first walk you through the evolutionary biological rationale for fasting and its studied benefits. We’ll then turn to the methods advanced by particular scientists and health practitioners in the field to see how fasting can be best implemented within your own lifestyle.
The Rationale Behind Fasting
I’ve talked briefly about the evolutionary biological rationale that supports fasting in a previous post that you can view here. In essence, the idea is that because humans have spent much of their time evolving as hunter-gatherers, we are therefore genetically disposed to certain dynamics of feast and famine.
Unlike today, our ancestors typically had to compete among themselves and with other species for a limited supply of food. In this context a survival advantage was conferredon individuals that were quick-witted, physically agile, and energy-efficient during periods of limited resource availability.
As pertinently phrased by longevity scientist Peter Attia: “If our ancestors couldn’t function when we were hungry, we wouldn’t be here”.
The 11,000–12,00 years that Homo-sapiens have resided within agrarian societies is far surpassed by the near 200,000 years that our species’ spent foraging and hunting. Viewed in this light, the period in which we have been eating the prescribed 3 meals a day represents mere fraction of the time during which our food sources were scarce and the timing of our next meal was unknown.
Since this time, numerous cultures and religions have emphasized the importance of fasting in some form of another. As early as 5th century BCE Greek physician Hippocrates recommended abstinence from food or drink for patients who exhibited certain symptoms of illness. Elsewhere around the world, fasting was used for the cultivation of religious experiences. Several groups located on the American continent fasted prior to major ceremonies connected with seasonal changes. In turn, the major religions — Christianity, Judaism and Islam — all advocate fasting during certain periods.
Evidently, fasting has a long track record within human society — so what are the studied benefits? Does the scientific evidence support the evolutionary biological rationale sketched above?
The Studied Benefits of Fasting
First and foremost, it’s important to note that the vast amount of scientific evidence in support of fasting has been deduced from animal studies. These studies have demonstrated that the lifespans of organisms from yeast and worms, to mice and monkeys can be extended by dietary intermittent fasting (IF). Research based on animal models has shown how IF/fasting can forestall and even reverse disease processes of various cancers, cardiovascular disease, diabetes, and neurodegenerative disorders.
Although it’s tempting to take these incredible findings at face value, the observed benefits of fasting in animals shouldn’t be equated with the benefits of fasting in humans. Emerging evidence based on human studies indicates that we undergo many of the same molecular, metabolic, and physiologic adaptations typical of these animals when exposed to IF. This being the case, these adaptations to fasting often are not as acute in humans or as well understood. For example, it would be erroneous to assume that because implementation of a fasting regime in rodents resulted in a 20% increase in lifespan that we can expect to add a couple of decades onto our own by virtue of doing the same.
With this in the back of our mind, let’s explore four of the positive effects that fasting has been observed to have on the brain and body.
Autophagy can be conceived of as a process of cell purification and cleansing. It is an adaptive mechanism to stress in which defunct and potentially harmful cells are consumed by their healthier counterparts, thereby serving to prevent and repair molecular damage.
Autophagy has been recognized as a crucial defense mechanism against cancer malignancy and neurodegenerative diseases. More recently, autophagy has also been observed to limit the replication of viral infection.
When mammals and other organisms ingest meals ad libitum, their cells receive a steady supply of nutrients and so remain in a state of growth — protein synthesis is robust and autophagy is suppressed. Starvation from macronutrients — ie fasting — disrupts this cycle and has therefore been found to induce autophagy in a highly efficient fashion.
2. Fat Metabolism and Ketone Production
The adaptive mechanisms behind fasting involve a metabolic shift to fat metabolism and ketone production. Ketogenesis occurs when the body switches from utilizing glycogen derived from carbohydrates to utilizing ketone bodies derived from fat.
In recent years, there has been a ground-swell of interest into the benefits associated with the ketogenic diet — a diet in which carbohydrate intake is severely limited and fat intake increased to encourage the body to metabolize the majority of its energy from fats. Ketones are considered a better source of energy for the brain because they cause less oxidative stress and they last for longer.
Emerging findings from human studies indicate that different forms of fasting may help to reduce weight by encouraging the body to utilize its fat-stores to produce energy. In humans the liver serves as the main reservoir of glucose, which is stored in the form of glycogen. Depending on an individual’s level of physical activity, 12 to 24 hours of fasting has been observed to result in a 20% or greater decrease in blood sugar and liver glycogen stores. This is accompanied by a switch to a metabolic mode in which fat-derived ketone bodies and free fatty acids are used as energy sources.
In essence, this means that your body becomes more proficient at utilizing fat derived from its own adipose tissue (body fat) the longer you remain fasted. Through this process, the majority of human beings are capable of surviving 30 or more days in the absence of any food.
In a famous study conducted in 1965, a morbidly obese male patient weighing over 200 kilograms fasted under supervision for an astounding 382 days. By the conclusion of the study the patient had attained what was considered to be a healthy physique.
3. Increased Levels of Human Growth Hormone (HGH)
Human Growth Hormone (HGH) is a protein secreted into the bloodstream by the pituitary gland. HGH serves many functions throughout the body. It boosts protein production, promotes the utilization of fat, and interferes with the action of insulin. Endogenous production of HGH typically peaks during adolescents and begins to wane as we age.
During our latter years, HGH deficiency is matched by reduced protein synthesis and lean body and bone mass as well as increases in body fat. It is therefore believed that reduction of endogenous HGH production may account for one or more of the above effects of aging.
Studies have proven that there is a multiple-fold increase in endogenous levels of HGH when we enter a fasted state. The body’s boosted levels of HGH is regarded as an adaptive stress response to caloric deprivation and acts as a principal mediator of protein conservation. In other words, elevated levels of HGH encourages muscle retention during a fast and growth upon re-feeding post fast.
4. Cognitive Function and Brain Health
Contrary to popular perception, humans retain and may even experience enhanced cognitive function when starved of nutrients for short duration. The mechanism behind this trait is attributed to increased signalling of brain-derived neurotrophic factor (BDNF) that occurs when we are fasted.
BDNF is one of five neurotrophins — a group of proteins that facilitates the survival, development and functions of neurons. BDNF in particular plays a vital role in the maintenance of the central and peripheral nervous systems, acts as the master regulator of energy homeostasis and encourages neuroplasticity –your brain’s ability to form new neural connections throughout life.
Conversely, diminished BDNF signalling has been linked to the development of age-related neurodegenerative disorders, including Alzheimer’s and Parkinson’s diseases, psychiatric disorders and major depression.
A growing body of literature into the effects of acute moderate exercise on cognitive function suggests that exercise is a fundamental cognitive enhancer. It is theorized that the signalling of BDNF may therefore have evolved to play a role in cognition-enhancing effects of running and intermittent food deprivation in hunter-gatherer groups.
In short, by acting as a metabolic stress on the body, fasting encourages the signalling of BDNF thereby facilitating optimal brain health.
Approaches to Fasting
The positive bodily responses highlighted above are just a few of the researched benefits associated with fasting. As the practice generates greater interest from the scientific community in the coming years, our knowledge on the topic is bound to only increase. Already mainstream medical practitioners are incorporating fasting into their treatment methodologies.
At this stage you may be interested in trialing fasting yourself. So how should you go about doing this?
Although the benefits cited above are generally compounded the longer you fast, it is important to approach fasting slowly and allow time for you to assess how your body is reacting. Do not expect to jump straight into a multiple day fast and feel great. Indeed results of fasting trials in human subjects suggest that there is a critical transition period of 3–6 weeks during which time the brain and body adapt to the new eating pattern and mood is enhanced.
It is also important to note that we are all highly heterogeneous with regard to our genetic composition and the environmental factors to which we are exposed throughout life. There will be considerable variability among individuals in the response to different eating patterns. Furthermore, everyone has different commitments in relation to work and family life that will undoubtedly impact on the feasibility of maintaining a healthy fasting regime.
Finding the right methodology to suit your lifestyle is key to making fasting a continued practice. Below are some of the approaches to fasting advanced by researchers in the field.
Circadian Clock Time-Restricted Feeding
Time Restricted-Feeding (TRF) is a method advanced by Dr Satchin Panda of the Salk Institute for Biological Studies. In most organisms that have evolved on Earth, the biological clock, or circadian oscillator coordinates behavior and physiology in accordance with natural light-dark and feeding cycles. When the circadian clock is out of sync — which can happen when we fail to attain adequate sleep or eat late at night for example — our health can be significantly jeopardized.
In line with our circadian clock, the basic idea behind Time-Restricted Feeding (TRF) is to finish eating as close to sunset as possible and maintain a minimum 13 hour fasted window. For those of us residing in polar regions where the sun might not ever set or rise, this might mean finishing dinner at 6:00pm and having your first bite of food or sip of coffee at 7:00am.
The researchers at the Salk Institute for Biological Studies have even established an app that can help you keep track of your daily eating behaviors. As an added bonus (for the science lovers out there), the data that you share through the app will help researchers understand how daily timing of eating behaviors influence health and well-being as part of a larger study.
You can find the app here.
Starting off with a 13 hour fasted window is a good way to initiate your body into a fasting practice as feelings of hunger/cravings can be successfully managed within such a time-frame. It is important to note that your body will become more efficient at utilizing fat for energy and operating with minimal caloric intake the more times that you fast. Feelings of hunger will gradually diminish as your body adapts to the change in eating patterns. If you feel comfortable operating in line with TRF, then you might want to try an extended fasting window.
This is perhaps the most well-known method to fasting. The 16:8 protocol entails eating within an 8 hour window and fasting for a total of 16 hours. As a general rule of thumb, the health benefits of a fast become more pronounced the longer you abstain from food. At around the 16 hour mark of a fast the body begins to derive its energy from fat and autophagy ramps up significantly.
This being the case, most people don’t want to forgo food for longer than necessary and 16:8 means you only have to skip a single meal while still racking up some significant benefits.
Most people opt to finish dinner at around 8:00pm, skip breakfast and break their fast with lunch at 12:00pm the next day. In saying this, it really depends on what works for your schedule. If you prefer to eat dinner earlier and enjoy breakfast too much — or vice versa — simply push the fasting window forward/back as necessary.
The Fasting-Mimicking Diet (FMD) was created by Dr Valter Longo, Director of the Longevity Institute at the University of Southern California. As part of the FMD, you consume a low calorie diet comprised of specific natural ingredients for a period of five days. Given the choice of ingredients and the low amounts that you consume, the benefits associated with strict fasting are not overly jeopardized allowing you to reap many of the benefits of a multiple day fast.
Although FMD stands as a scientifically backed and endorsed fasting protocol, it is somewhat ominous that it is only from Prolon — the sole company that advertises the method — that you can buy the required nutritional packages. I caution against paying exorbitant prices for items that supposedly assists you in fasting. It is somewhat counter-intuitive to pay for something beneficial for our health that we can do for free.
Fasting is a practice as old as our species, but many of the researched benefits are only just starting to emerge. There is great potential for the incorporation of periodic fasting during adult life to promote optimal health and reduce the risk of many chronic diseases particularly for sedentary and overweight individuals. This being the case, everyone will vary in their reaction to a fasting protocol given differences in genetics and lifestyle and the practice must therefore be approached with care. Again, consult with a medical expert if you intend to give fasting a shot.
Alex Goik commonly writes for Mogul News and at Foreign Affairs Navigator where he strives to offer fresh perspectives on foreign affairs, tech and China (coupled with the odd analysis of human nature).
By The Ascent