Fasting For Beginners

by Sasun Bughdaryan on Unsplash

For most of human history, missing a meal was not a choice. It was Tuesday.

Yet today, the mere thought of going without food even for twenty-four hours triggers something close to existential dread. We do not fear the hunger itself. We fear the anticipation of it. The imagined weakness, the fatigue, the gnawing pain that has not even arrived yet.

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This is a remarkable paradox. Our ancestors spent the better part of two hundred thousand years navigating feast and famine with bodies exquisitely engineered for exactly that rhythm. The hunter who fell apart at the first growl of an empty stomach did not survive long enough to become our ancestor. We are, each of us, the descendants of people who were very good at being hungry. Fasting, for our ancestors, was not a wellness choice. It was a survival superpower.

And yet here we are: creatures of unparalleled cognitive sophistication, managers of global supply chains, conquerors of smallpox and scurvy, paralyzed by the thought of skipping lunch.

Our biology has not changed. What changed is the story we tell ourselves about discomfort. Modern life made us an offer we did not know we were accepting: maximum convenience in exchange for an ever-shrinking tolerance for discomfort. We have engineered discomfort out of existence so thoroughly that when it reappears, our ancient brain registers it not as a normal signal, but as a threat to survival.

And that brain is worth understanding because it is doing precisely what it was designed to do. The same survival software that carried our ancestors through ice ages, famines, and predators is still running in the background of modern life. We are its masterpiece, and also its hostages.

The Oldest Medicine

Long before it entered a laboratory, fasting had been independently discovered by physicians, philosophers, and priests on nearly every continent, in nearly every era.

Vedic and Jain traditions were linking deliberate abstinence from food to purification and nonviolence as far back as 1500 BCE. The Abrahamic faiths absorbed the practice and gave it new meaning. Moses, Jesus, and Muhammad each taught, in their own way, that fasting the body could cleanse the soul. Buddhist monks have long treated it as a tool for sharpening the mind and spirit simultaneously. Indigenous peoples of North America fasted before Vision Quests. Evenk shamans in Siberia fasted to deepen their visionary practice.

Across cultures, across millennia, across belief systems that did not agree on many things, human beings kept arriving at the same conclusion: hunger, deliberately chosen, did something to a person. Something useful. Something important.

The Greeks were early to this intuition. Hippocratic writings from the 5th century BCE describe the deliberate restriction of food during illness. The logic was elegant: overeating while sick burdened a body already fighting to restore itself. Plato and Aristotle, never men to agree on everything, found common ground here. Both considered moderation in diet foundational, not just to physical health, but to moral character, a reflection of who you were.

Half a world away, Traditional Chinese Medicine arrived at a similar conclusion through an entirely different framework. Daoist health practices recommended periodic food abstention to regulate Qi and restore the body’s natural harmony, a sophisticated intuition millennia before anyone had heard of insulin or autophagy.

The practice never disappeared. It simply went underground. Then, in the 19th century, it began resurfacing in Western medical thinking. The physician Edward Hooker Dewey, in his 1895 work The True Science of Living, made a provocative argument: that many diseases were not the result of too little food, but too much of it. His work was controversial, but as it turns out, pointed in the right direction.

Today, stripped of predators and famine, those same mechanisms that ensured our ancestors’ survival now serve a different but equally compelling purpose: longevity.

The Sharpening

Early humans lived entirely within nature’s feast-and-famine cycles. Food was scarce, infrequent, and often times, faster than the people trying to catch it. Over millennia, the human body evolved a sophisticated metabolic flexibility, the capacity to sustain physical and cognitive performance precisely when food was nowhere to be found.

The brain adapted to support this. Dopamine pathways drove exploration, risk-taking, and creative problem-solving, not in spite of hunger, but because of it. Our ancestors survived because during periods without food, they were the ones who became sharper, more alert and more inventive. The body, deprived of its usual fuel source, shifted into a higher gear.

And this is the part worth sitting with. The anxiety, the irritability, the near-panic that many people experience at the first sign of hunger today is not weakness. That is ancient software executing exactly as written. The dopamine-driven alarm system that screams FIND FOOD! FIND FOOD NOW! is the same system that kept your ancestors alive. It is extraordinarily good at its job.

The problem, and the blessing, is that for most of us, the job no longer exists.

The World Our Ancestors Dreamed Of

We now live in conditions that would have been unimaginable to every human who came before us. Climate-controlled homes. Hot water on demand. Artificial light at any hour. Food available twenty-four hours a day, in quantities and varieties that no previous generation could have conceived of. We watch survival programmes from our sofas, snacking, vaguely aware that we should probably do more exercise.

In this world, skipping a meal is not a necessity. It is not even a consideration. And when someone suggests stopping eating at four or five in the afternoon, the response is often genuine disbelief, as though something that our species did for hundreds of thousands of years has become, somehow, radical.

And when many people do attempt it, something predictable happens. The first hunger pang arrives, not starvation, not danger, just the ordinary signal of an empty stomach. And the ancient alarm fires. Panic sets in. The fast collapses. Sometimes it collapses into overeating, the body compensating for a threat that was never really there.

This is not a failure of willpower. It is a mismatch of hardware and environment, playing out in real time. Our technology has so dramatically outpaced our biology’s ability to adapt that we now find ourselves running ancient threat-detection software in a world it was never designed to navigate. Our brains have not received the memo that the danger we face today is not starvation. It is the unshakeable belief that we cannot survive a single uncomfortable afternoon without a snack.

The Discomfort Zone of fasting is not new territory. It is the oldest territory there is. We have simply forgotten that we were born to live there.

What Actually Happens When You Stop Eating

So what actually happens when you stop eating? The body does not simply wait for its next meal. It shifts through a precise, elegant sequence of metabolic states, a programme written over two hundred thousand years of evolution, still running in every one of us.

Understanding this sequence does not just make fasting more manageable. It makes it seem almost “magical”. Here is what to expect during the first 48 hours.

0 to 4 Hours: The Fed State

The body is processing your last meal. Blood glucose rises, insulin rises in response, storing excess glucose as glycogen in the liver and muscles. The body is in building mode, synthesizing proteins, banking energy. You are not hungry. Yet.

4 to 12 Hours: The Transition

Blood sugar begins to drop. Insulin follows. The body starts drawing on its glycogen reserves, spending from the account it just filled. Hunger comes and goes in waves, more like a knock at the door than a fire alarm.

12 to 24 Hours and beyond: Crossing the Threshold

This is where things get interesting. Glycogen stores are now depleted. Insulin levels drop. The body pivots to burning fat, converting fatty acids into ketones for fuel, a process called ketosis. To protect muscle tissue, growth hormone is released.

And somewhere around this time, cortisol rises quietly in the background. This is not a stress response in the psychological sense. It is the body mobilizing glucose from its remaining reserves, a practical housekeeping measure. For most people it is barely noticeable. For those who are already running on poor sleep, poor diet or chronic stress, however, this cortisol rise can amplify the discomfort of early fasting considerably, which is worth knowing before you conclude that fasting simply does not work for you.

Hunger intensifies in this window too. The stomach releases ghrelin, a hormonal signal to eat, and it is persuasive. This is the moment most people stop. What very few people know, however, is that ghrelin is not an escalating alarm. Research shows it peaks and then subsides to baseline within roughly two hours if you do not eat in response to it. The hunger wave, as relentless as it feels, is temporary and predictable. It is a test, not a trajectory. The body is checking whether food is available. When it determines that it is not, it gets on with the business of running on fat.

And somewhere between the sixteenth and twenty-fourth hour, something extraordinary slowly starts ramping up: autophagy. The body starts identifying damaged and redundant cellular components and breaking them down for recycling. It is, in the most literal sense, cleaning house. Meaningful autophagy activity in humans begins at forty-eight hours, though it is worth noting that precise timing in humans remains an active area of research. Individual variation based on metabolic health, prior diet, and activity level is significant.

24 to 48 Hours: Deep Fasting

This is where the magic happens. Full on Ketosis. Autophagy intensifies. Growth hormone rises 300-2000% over baseline levels: muscle preservation, increased fat burning, tissue repair, enhanced immunity. Many people report a shift towards calmness, a striking clarity of thought, brain fog lifting, sometimes dramatically.

A note on light exposure, because it belongs here more than most people realize. Blue light from screens, LED lighting, and fluorescent bulbs, particularly in the evening hours, suppresses melatonin production and disrupts restorative sleep and insufficient or disrupted sleep affects the hunger hormones which cause cravings for instant and easy energy like simple sugars and high calorie foods. Beyond sleep disruption, a landmark study from Northwestern University found that exposure to blue-enriched light in both morning and evening raised blood glucose and drove measurable increases in insulin resistance within thirty minutes of exposure, even in the complete absence of food. So that constant scrolling can challenge your fast, by increasing your hunger cravings.

It is also worth noting that emerging laboratory research in optogenetics has raised the possibility that blue light may have even more direct effects on pancreatic beta cells, potentially influencing insulin secretion through light-sensitive cellular pathways. This work is currently in the experimental stage, but the direction of the research is compelling and worth watching.

The practical implication of all of this is straightforward. During a fast, reducing screen exposure, wearing blue light blocking glasses, switching off electric light in favour of candle light or simply dimming and warming your light environment in the evening hours are simple, evidence-backed adjustments you can make to support the metabolic work of fasting.

The Electrolyte Story

During fasting is where electrolytes stop being a footnote and start being a main character. If you do not replace what is being lost, your experience will be more uncomfortable than need be.

In the early stages of fasting, as insulin falls, the kidneys begin excreting more sodium, a well-documented response known as the natriuresis of fasting. Water follows, leading to an initial loss of body fluid. As sodium and fluid drop, the body activates the Renin–angiotensin–aldosterone system to maintain balance by conserving sodium and excreting potassium. If sodium is not replaced, this hormonal response increases further, helping conserve sodium but driving additional potassium loss, which can worsen symptoms like cramps and weakness.

Insulin also influences magnesium retention. Lower insulin levels reduce magnesium slightly, although these changes are slower and less pronounced than shifts in sodium and fluid. People who are already insulin resistant or magnesium deficient before the fast may experience these shifts more intensely, contributing to more intense symptoms.

This is why hydration and adequate sodium intake matter during fasting. Replenishing sodium supports fluid balance, reduces the stress response, and may ease what is often called “keto flu.”The challenge is that these symptoms are non-specific. Fatigue, brain fog, headaches, dizziness, and cramps can all stem from sodium depletion, dehydration, or other electrolyte imbalances. The practical approach is simple. Take pinch of Celtic Sea salt under the tongue, followed by a glass of water throughout the day.

There is one more thing worth understanding about hydration here, because it runs counter to instinct. The problem during fasting is not dehydration in the traditional sense. You can be drinking plenty of water and still be running dry of what matters. Water without minerals is not hydration. It is dilution = mineral imbalance = symptoms. Keep sodium topped up, and potassium largely takes care of itself.

Celtic sea salt is worth reaching for over Himalayan pink salt, not for aesthetic reasons, but practical ones. Harvested from living coastal salt pans in Brittany rather than mined from ancient fossilized deposits, Celtic salt retains active moisture and a broader mineral profile, including meaningfully higher magnesium content. There is also the question of what mining introduces rather than what it preserves: heavy metal contamination in Himalayan salt is brand-dependent and dose-dependent, but it is a documented concern rather than a rumour. During fasting, both the mineral profile and the sourcing of your salt matter.

Magnesium

If muscle cramps, poor sleep, or a general sense of restlessness persist after addressing sodium and hydration, magnesium is worth a closer look. A magnesium glycinate supplement in the evening, in the range of 100 mg, is better absorbed and can support relaxation and sleep without the digestive side effects that come with forms like magnesium oxide or citrate. An Epsom salt bath or topical magnesium spray may offer additional relief.

Potassium

Potassium deserves a note of its own: handle with care. If your diet before fasting was reasonably balanced, your body usually keeps potassium within range during shorter fasts. Symptoms like persistent weakness, cramping, or a fluttering heartbeat may signal a need to address it, ideally through food rather than jumping straight to supplements. Clear vegetable broth is a gentle and effective option that won’t break a fast.

The principle throughout is this: support, do not override. You are not trying to outsmart your biology. You are simply giving your body enough of what it is losing so it can run the program smoothly.

A Note on Metabolic Flexibility

If you experience extreme fatigue, shakiness, irritability, or vision changes during fasting, your body is signalling that it is not yet adapted to fat burning. This is not failure. It is information.

The solution is not to push through. It is to build the capability first. Begin with a twelve hour overnight fast, which for most people simply means finishing dinner by eight and not eating until eight the following morning. Hold that for one to two weeks until it feels unremarkable. Then extend to fourteen hours. Then sixteen. Alongside this, gradually reduce sweets, refined carbohydrates, junk foods and in-between meal snacking from your daily diet. This accelerates the adaptation, because a body that is already accustomed to running lower on glucose makes the metabolic transition into fasting far more smoothly. The goal is to arrive at the fast already partly fat-burning adapted, so that the switch feels like a gear change rather than an engine failure.

AND remember….there will always be another fasting opportunity. Return when you are ready.

Breaking the Fast

How you end a fast matters as much as the fast itself. This is a perfect moment to kick the junk food to the curb. You’ve already shown you can go without, so now hit reset and start fresh.

The digestive system has been in a long, quiet rest. Digestive enzyme production has slowed, gut motility has reduced, and the mucosal lining has been in a state of repair rather than active processing. It does not need to be ambushed. Avoid raw vegetables, heavy proteins, dairy, processed foods, sugars, fried foods.

Eat small amounts, slowly, and give your body time to remember what it needs to do. Start with bone broth. Not because it’s trendy, but because it slips sodium and trace minerals back into circulation without asking the gut to do any real work. Just warmth, salt, and a gentle reminder that food exists.

Well-steamed vegetables: carrots, zucchini, spinach, are the right next move. Steaming collapses cell walls, doing half the digestive work before the food even arrives. A simple vegetable soup works beautifully here. Give the system something real without giving it a problem to solve.

An hour or two later, if the body is signalling comfort rather than protest, lean proteins and whole grains can return. The fast taught patience and re-feeding should honour that.

The Oldest Territory

Let’s bring it back to the point that actually matters.

Everything described, the ghrelin wave that peaks and passes, the cortisol nudge, the electrolyte shifts, the hunger that feels like a five-alarm emergency but is essentially just your body doing housecleaning, is the ancestral brain performing its job with great enthusiasm and absolutely no self-awareness. It is not sabotage or weakness. It is a survival system running a program that kept your entire lineage alive across two hundred thousand years of genuine scarcity. Honestly, it deserves some credit. Just not your obedience.

Because here is what that ancient alarm system fundamentally cannot do: think. It is extraordinarily, impressively loud, but it cannot distinguish between a genuinely empty savanna and a fully stocked kitchen you have simply chosen to ignore.

The difference between someone who quits at hour fourteen and someone who moves calmly through to hour forty-eight is not willpower, discipline, or some rare genetic gift. It is understanding. The person who knows the hunger wave is temporary rides it like a wave. The person who doesn’t, rides it straight off a cliff into a bowl of pasta.

You cannot silence the ancestral brain. But silence is not the point. The point is the moment between the scream and the response. That gap, small, almost invisible, gone before most people notice it, is where everything interesting happens. Psychologists call working within it cognitive reappraisal. Those who find it, usually stumble across it on the other side of something hard. Something they nearly quit. And the thing that surprises them most is that it follows them out into the rest of their life. Into the difficult conversation they stopped avoiding, the early morning they finally stopped negotiating with, the version of themselves they had long suspected existed but never quite trusted enough to meet.

Survive the discomfort once, deliberately and something quietly shifts. Your brain files it under things I can do. That folder, once opened, has a way of filling faster than you expect. And every entry in it traces back to the same moment: the one where you chose discomfort despite every instruction from your ancestral brain loudly and with complete conviction trying to convince you that you absolutely should not.

How to Begin Fasting

Most people make fasting harder than it needs to be.

You don’t start with a 24-hour fast. You start smaller—by teaching your body to go a little longer without food.

Prepare Your Body

Before you fast, make things easier on yourself:

Cut back on:

• Alcohol

• Sugar and juices

• Refined carbs (white bread, pasta, rice, pastries)

• Processed foods

And just as important:

Stop snacking between meals.

This alone starts to stabilize your hunger and makes fasting feel much more natural.

You can also support your body by:

• Taking magnesium bisglycinate (start low, work up to ~400 mg/day)

• Adding a small pinch of sea salt before drinking water to help with electrolytes

Start Small: Skip One Meal

This is the first real step.

If you eat three meals a day, skip one.

That could look like:

• Skipping breakfast

• Skipping lunch

• Or finishing dinner early (around 4–5 pm) and not eating until the next morning

That’s it.

You’re not “fasting hard”—you’re just giving your body a longer break from food.

Build to a 24-Hour Fast

Once skipping a meal feels normal, you can extend it.

For example:

• Finish eating at 5 pm

• Eat again at 5 pm the next day

No snacking, just water and electrolytes.

Go a Bit Further (Optional)

If that feels good, you can stretch it further:

• Stop eating at 5 pm

• Fast through the next day and night

• Eat breakfast the following morning

That’s about a 36-hour fast—and most of it happens while you’re asleep.

A Simple Rule

Stay hydrated.

Water matters. Electrolytes matter.

A small pinch of sea salt before drinking water can help you feel steadier, especially as you go longer without food.

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