The Physical & Spiritual Dimensions of Fasting
What do Jesus, Muhammad and the Buddha have in common? Indeed, they all had an impeccable fashion sense. If I had my druthers, I would don a diaphanous saffron robe as an indication of my spiritual pursuits. However, there is a consilience among these prophets unrelated to style. All three of these mystics embarked on walkabouts — solitary journeys of contemplation, discovery and self-inquiry. Jesus to the desert, Muhammad to the cave, Buddha through the mountains of Nepal. Furthermore, as part of these spiritual inquests, they all suspended their consumption of food.
As Jesus confronted Satan, he was tempted neither by the devil’s offerings nor by lunch. Muhammad intermittent fasted on the regular (the white days). In fact, in Islam, fasting (sawm) is a requirement for attaining God-consciousness and one of the five pillars of the faith. And it is said that the Buddha existed for a time, prior to his Bodhi tree revelation, on a singular daily grain of rice.
Many religious traditions are built upon the notion that transcendence rests upon the perceived duality between spirit and body. We must eschew the carnal and corporeal for it is conjured from dust and to dust it will return. Any object that takes form is ephemeral and subject to decay. Hence, we lift ourselves up and out of our impermanence and into the eternal spiritual realm. We sublimate the appetite to grasp the infinite and find enlightenment.
One not need, however, be a follower of ancient scrolls to observe how cycles of fasting and eating are inherent to life’s foundational fabric. The oppositional states of abundance and scarcity, growth and repair, and wakefulness and sleep are part of nature’s course. Over hundreds of thousands of years, humans have evolved adaptively in relationship to these environmental prerogatives. For example, humans have developed genetic pathways that signal the body to store fat in anticipation of the impending winter — an imposed sort of fast. (I go into great depth on this topic in my interview with Dr. David Perlmutter.)
Sleep, which on the surface, might appear rather imprudent (leaving us susceptible to saber-toothed beasts roaming the savannah) and wasteful (we’re not gathering food or pro-creating) became adaptive. Now we understand that sleep is integral for physiological and psychological restoration, memory consolidation and the cleansing of dysfunctional brain cells via the glymphatic system.
But what happens when culture outpaces evolution? What happens when there is 365–24/7 abundance regardless of seasonality? By no means am I discounting the existence of famine, but there is little doubt that we live in a world in which the abundance of refined sugar and refined grain kill more people than food scarcity. The over-consumption of these “foods” directly contribute to the epidemics of the four biggest chronic disease killers: heart disease, cancer, diabetes and neurodegenerative disease.
The disappearance of scarcity due to modern industrial agriculture and globalization gives our bodies a singular message: grow. And this monotone dispatch comes at the expense of repair. The modern Western world tends to sanctify the notion of growth. Bigger is better — certainly in America. But you don’t want cancer to grow in your pancreas or fat to grow in your liver. You don’t want beta-amyloid proteins to accumulate in your brain. And you don’t want advanced glycation end-products to form in your bloodstream.
In order to balance bulging biceps with cardio-metabolic health, some people (including yours truly) are beginning to “engineer” scarcity in the form of intermittent fasting (or time-restricted eating). Fasting is part of an emerging collection of adoptive behaviors called adversity mimetics that trigger positive “hormetic” responses in the body. It draws its wisdom from the Nietzschian adage, “that which doesn’t kill you makes you stronger.” Other adversity mimetics include cold or heat therapy, high-intensity interval training and intermittent hypoxia (long breath holds). There are myriad physiological benefits to “eustress” (good stress) associated with fasting, some of which I will elucidate in this essay.
Fasting can take on many forms (from austere month-long water fasts to weekly 24-hour fasts). Any fasting protocol should be discussed with your primary care physician (particularly if you are pregnant or nursing). Regardless of which specific protocol you adopt, I believe fasting should be integrated slowly to allow your body to acclimate to a new feeding schedule. I will be referring to the 16–8 time-restricted eating protocol as researched by Satchin Panda’s lab at the Salk Institute.
Here’s my daily regime (and I’m not neurotically fundamentalist about it): I consolidate all of my eating in an 8-hour window between 11am — 7pm. I take advantage of sleep as a de facto 8-hour fast while also maintaining some small semblance of a social life. It’s become quite easy for me not to eat in the morning. I drink plenty of lemon water (lemons and limes are effective glucose disposal agents). I do consume a rather vulgar concoction of greens (replete with pre-biotic fiber, phytonutrients, adaptogens) with turmeric extract (an anti-inflammatory) which I have estimated to be around 50 calories. I can burn that off in a few trips up and down my extensive outdoor staircase. And I drink an espresso about an hour after I wake up.
Everyone is different but if you are interested in fasting here are some general rules of thumb: You always want to wait at least one hour after you wake up before eating. And you ideally want 3 full hours of digestion prior to sleep. Sleep, of course, is a non-feeding period but, just because you are not eating doesn’t mean your body has gone into a fasted state. If you ate a huge meal an hour ago, your body is still spending considerable energy digesting and metabolizing food.
I combine intermittent fasting with a vegetarian ketogenic diet (with occasional omega-3 rich fish). I’ll preserve a deep dive on diet for another essay but it is very related, specifically as it pertains to blood glucose levels. Everyone is different — but I can categorically claim that the consumption of refined sugar, refined grains and processed meats are going to lead to high blood glucose levels (hyperglycemia), which is the pre-cursor for Type 2 diabetes and heart disease.
Here’s a brief primer metabolism and blood glucose. Your body needs energy to function. Fortunately, we all have our own energy-producing power plants called mitochondria. Each cell in our body contains approximately 2,000 mitochondria that produce energy through a 3-part process called cellular respiration.
Your body generally uses glucose (from carbohydrates) to generate energy in the form of ATP (adenosine triphosphate). Glucose is absorbed through your small intestine into the bloodstream and ushered into your cells by a peptide hormone called insulin, which is secreted from your pancreas. If you have too much serum glucose (because you scarfed down a soda with a bowl of pasta), your pancreas will need to produce more insulin to do its job. If this pattern continues, then eventually your cells become stingy about letting glucose in and you become insulin resistant.
When high levels of glucose are abandoned in the bloodstream, a few things can happen, including:
1) some glucose can get stored in the liver as glycogen (for a rainy day)
2) glucose will get converted into triglycerides and stored as adipose tissue (fat)
3) glucose will combine with hemoglobin (the protein in your blood famously tasked with shepherding oxygen to your cells) to form a glycoprotein that is inflammatory to your vascular system. High blood sugar levels are concomitant with diabetes, which is correlated with cardio vascular disease and dementia. In short, this is why sugar can be considered the world’s most dangerous assassin.
Fasting activates a number of different process.
Burning Fat: When you fast, blood glucose levels plummet. Low glucose levels (hypoglycemia) triggers insulin’s “yang,” a peptide hormone called glucagon (who, given its non-celebrity status, could benefit from a better public relations agent). This protein, also secreted from the pancreas, prompts a few processes
1) the release of glycogen (stored glucose) from the liver
2) a process called gluconeogenesis (the endogenous production of glucose in the liver), and
3) lipolysis, the breakdown of triglycerides (fat) into free fatty acids (and glycerol) to produce energy.
In other words, instead of your mitochondria burning glucose for energy, it burns fat. This process is also associated with ketosis in which some free fatty acids become “ketones” that brain cells can leverage for energy production. Ketones have the additional benefit of reducing the production of “free radicals” and reactive oxygen species during energy production. (I go deep on ketones with Dr. Stephen Gundry here).
The benefits of fasting go well beyond burning fat.
Weight Loss: One of the by-products of fasting can be weight loss — though this obviously depends on the amount and quality of the food you eat during the feeding window. Generally, one tends to consume less calories (and the “right” calories) when one is focusing close attention on behavior like a fasting protocol.
Further, you can eat the EXACT same diet and maintain weight in a 24-hour feeding cycle while losing weight in a time-restricted protocol. If you want to go deeper on fasting and metabolism, here’s a link to a series of highly stringent studies conducted by Panda and his lab.
For the vain among us, weight loss can obviously help you look “better.” But losing weight in the form of visceral fat has more profound benefits. Oxidation of adipose tissue lessens the work load on the heart and reduces inflammation and cytokine activity.
Microbiome: In your large intestine, there are 39 trillion bacteria that mediate a wide variety of physiological systems from digestion to immunity to mood regulation. These bugs are separated from your bloodstream (and most of your immune system) by a microscopically thin epithelial wall. The breakdown of the integrity of the tight junctions that make up this wall is called intestinal permeability (leaky gut!).
When your gut is leaky, endotoxins seep into your bloodstream eliciting an inflammatory response. If dysbiosis (disruption of the gut microbiome) and permeability persist, you can end up with chronic inflammation. Your body can also begin attacking itself. Auto-immune diseases such as ulcerative colitis, intestinal bowel disease and Crohn’s disease are increasingly common due to poor gut health.
Research into the impacts of fasting on the microbiome is still preliminary and confined primarily to in vivo mice studies. However, there is some early data that demonstrates that time-restricted feeding can lead to an increase in Akkermansia (a beneficial bacterial strain) as well as an uptick in the production of butyrate, a short chain fatty acid produced by bacteria that promotes epithelial integrity and upregulates insulin sensitivity.
Cellular Clean-up and Recycling: Fasting is a signal that activates a cellular pathway known as AMPK. In low energy states, AMPK opposes mTOR (a pathway for cellular growth). This inhibition triggers autophagy — the body’s system for cleaning out dysfunctional cells. Essentially, damaged proteins are broken down into their amino acid building blocks that can then be recycled by your cells for new protein synthesis. The housekeeping process is a crucial cellular process for longevity.
Mitochondria: Mitochondrial activity declines with age, but AMPK activation also counteracts this decline by triggering mitochondrial biogenesis, the production of new, healthy mitochondria. Having greater numbers of healthy mitochondria as we age may protect against age-associated declines such as cognitive dysfunction.
DNA Expression: Every cell in your body contains DNA, which has a fixed nucleotide sequence that is unique to you. Your DNA “expresses” itself by giving protein recipes to RNA, which ventures out of the cell nucleus into the cytoplasm and delivers these transcriptions to your ribosomes that, in turn, produce proteins. While your DNA is fixed, its expression is not. Your “epigenome” marks your DNA in a manner that influences the timing and content of its recipes. To use a musical analogy, your DNA are the piano keys, your epigenome is the piano player.
Fasting activates sirtuins, a family of seven proteins that regulate cellular function and gene expression. Sirtuins are virtuoso pianists in that they help to maintain proper genomic expression. They also upgrade mitochondrial function and suppress tumor growth. The Australian biologist, David Sinclair, famously demonstrated that depriving yeast of calories significantly extended their lifespan.
Parenthetically, eating plants rich in polyphenols (like resveratrol) may also activate sirtuins and, not surprisingly, the plants that are highest in these phytonutrients are the most “stressed” ones. Plants, like humans, can positively respond to low-grade stressors (like drought) and generate self-protecting compounds. Grapes used for the production of wine are often purposefully stressed by vintners. Hence, wine (specifically pinot noir) contains resveratrol (but not nearly enough to have a significant impact). One can supplement with resveratrol (and NMN (the pre-cursor to NAD+)) to stimulate sirtuin activity.
Anti-oxidant Production: Recent studies in mice have shown that fasting increased NRF2 binding. NRF2 is a transcription factor that induces mRNA expression related to the production of anti-oxidants like glutathione. Glutathione neutralizes “free radicals” that can lead to oxidative stress in the body. This is also key to longevity.
In short, fasting improves metabolic function and addresses many of the hallmarks of aging.
Even though I don’t subscribe to dualistic traditions that divide body from soul, there is a quality to fasting that is patently beyond the physical. It is a spiritual pursuit. When I started the 16–8 protocol, I had a craving not to crave. Of course, this is a paradox. But I didn’t want to incessantly pine for external agents to satiate my perceived and sundry needs. After about 2 weeks, I stopped feeling unnecessarily hungry. I unwound the habit of mindlessly eating.
And if one can stop craving food then one can certainly stop instinctively grabbing for their phone or the wine bottle or the credit card in search of ephemeral pleasure. Fasting, as a practice, is applicable well beyond food. As Buddha instructed, the cessation of craving is a stepping stone to nirvana, to liberation.