Chapter 6: Fasting


Why You’re Fat and Sick

The song Rock Star by Nickelback features the lyrics “… we’ll all stay skinny ’cause we just won’t eat….” I interpreted that song as a satire about the excesses of the rock star lifestyle. Still, that particular lyric makes much sense if you dig into the science and ignore the conventional wisdom on fasting.  If your body doesn’t need nutrients, then don’t eat.

If your mind works like most modern Western folks, you immediately recoil from this idea.  That’s crazy!  If you don’t eat, you will die, so the visceral thinking goes.  We have it deeply ingrained in our psyche that if you don’t eat very frequently, you will fall over dead.  Your flight from New York to Los Angeles surely would have been fatal if you didn’t eat those peanuts mid-flight.   Jesus fasted for forty days in the desert, but he could only do that because of his divine powers.  These notions are patently false, so where did our collective mind get them?  As a culture, we’ve been brainwashed by the food industry.  Think about those commercials that suggest dire consequences from not eating (preferably a lot of sugar) frequently.

Fasting is a biological adaptation to hard times, and there have been plenty of hard times in human history.  If you are a hummingbird, you must eat all the time to stay alive.  If you are a human being with some body fat stores, you just switch to burning that for fuel.   That switch is rusty and hard to flip for many of us because we’ve never done it.  The average modern human never fasts for more than 8 hours at a time, so we’re always running on sugar.  I argue that we can and should run off fat a significant portion of the time.  Our society is very blessed, and those abundant blessings have led to dietary excess.  That dietary excess has led to obesity and metabolic syndrome, making us sick and vulnerable to many ways to die.  Fasting is an excellent tool for reversing the consequences of dietary excess.

If you are scientifically minded and like the technical stuff, you probably wouldn’t be reading this book.  I wrote it to simplify and summarize these very technical topics in a relatively short space.   But if you want more information, look no further than The Obesity Code by Dr. Jason Fung.

Dr. Fung isn’t some crazy YouTuber trying to sell you some snake oil.  He’s a serious kidney doctor that got tired of watching his patients get sick and die while he watched.  He’s done a lot of work using “time-restricted eating” to reverse metabolic syndrome and save his patience.  His essential treatment is controversial: He suggests you don’t need three meals and three daily snacks.  He goes so far as to say if you are sick and fat, you probably don’t need any food for large portions of time.

What Dr. Fung (and legions of others) suggest is what is commonly called fasting.  If you want a thorough treatment of what fasting is, how it works, and how to do it step by step, check out Dr. Fung’s book Complete Guide to Fasting.  You can also learn much about this fascinating practice by finding Dr. Pradip Jamnadas on YouTube.  Dr. Jamnadas is a cardiologist that (like Dr. Fung) got tired of watching his sick patients get sicker and sicker.

In an interview with Dr. Rangan Chatterjee, Dr. Jamnadas talks about the benefits of fasting that he actually observed in his own patients.  Remember that he talks about real sick people, not theoretical conjecture in a biochemistry textbook.  He states that other diet programs simply don’t work, but fasting does.  He goes on to say that he observed decreases in blood pressure, decreases in diabetes, improved cardiac health, improved muscle tone, and stronger bones, just to name a few. (This was your humble author’s experience as well).

We can take from all of this that fasting benefits metabolically sick people and is free of charge.  Why, then, do most doctors discourage the practice?  In addition to the reasons outlined in the Why Do They Lie section of this book, Dr. Jamnadas believes that doctors resist fasting as a treatment because all of the work falls on the patient. Doctors can’t do anything besides offer advice.

To be effective, fasting requires changing how the patient thinks about food.  That requires education, which is very time-consuming.  It doesn’t work well with the assembly line model of medicine, which makes medical practice very lucrative.  For this reason, medical doctors aren’t willing to dive deeply into the patient’s lifestyle required to prevent disease.  Most doctors are only interested in treating disease and doing it as quickly as possible.

This prescription is challenging.  Most of us have been conditioned to think we need to eat every couple of hours and to eat mostly poison (albeit tasty poison).  In an age of plenty (fries with that cheeseburger and coke?), it is challenging for most people to intentionally create scarcity within their lives.  Yet, humans have been doing it for thousands of years to good effect.  Most of the world’s religions incorporate fasting as a path to spiritual growth or enlightenment.  Many of us do it in the religious context.  Muslims, Hindus, and Catholics all observe some kind of fast. Jesus fasted for 40 days in the desert.

A mostly healthy person will not experience blood sugar going too low.  This is because the body will generate enough glucose to maintain brain function and does this out of fat.  You don’t need carbs for anything at all.  It is not a necessary nutrient.  The exception to this is the use of drugs that impact insulin.  If you are being treated for diabetes, do not attempt any sort of diet modification or fasting without consulting your physician.  Fasting and insulin must be carefully monitored.  They are wrong when a relatively healthy person says they need to eat because their blood sugar is dropping.  They don’t need to eat.  They just need to become adapted to burning fat.

The Logic of Fasting

It is important to remember that most obesity is a byproduct of metabolic syndrome, not the other way around. When you don’t eat, your brain stops sending signals to the rest of the body that food is coming.  Without those signals, insulin production grinds to a halt.  That is the utterly simple purpose of fasting: to stop insulin production.  Sure, other beneficial things happen, such as dramatic weight loss, but that isn’t enough to fix your metabolic illness. Get your insulin under control, and a sensible diet will take off the pounds quickly.  In a sense, you are eating when you’re not eating–you’re just eating your own fat.

Insulin resistance can be reset by giving everything a rest.  Each time you stop insulin production for a period, your body becomes more sensitive to insulin.  This may not hold in the advanced stages of diabetes, where too much damage to tissues has been done, but most people will show an improvement.

The benefits of fasting are profound and widely recognized among medical professionals.  Many of the biomarkers that improve with exercise are known to improve with fasting.   Both reverse the consequences of dietary excess.  Good evidence of this recognition is that many people are working on “fasting-mimicking” diets.  Fasting works, but it takes hard work and dedication.  What if we could do that without the effort?  Pharmaceutical companies are working on drugs to mimic the effects of fasting.  We always want that magic pill.  Given the state of the art today, the best way to achieve the results from fasting is to, you guessed it, fast.

Is It Safe?

To say fasting is dangerous is just plain stupid.  Every human being on the planet fasts.  We call it sleep.  If you can eat in your sleep, I suggest making an appointment to discuss it with your doctor.  What do most people do first thing in the morning?  They break their fast–breakfast.   So the average person fasts for about 8 hours every day.  So if we are to claim that fasting is unsafe, we must be talking about some specific timeframe in which it becomes so.  That, too, is arbitrary and stupid up to the point that the body runs out of some essential nutrients.  As long as you have everything you need, what good does it do to add more?  This is a space where a little common sense can go a long way.

When I was a kid in the 1970s, naughty boys were often punished by being sent to bed without dinner.  I can’t find a single example of a case where any of those badass little boys died.  Skipping a meal, it turns out, is a very healthy thing to do.  Contrast the practice of fasting with starvation.  Fasting is a choice to deprive yourself of food for some purpose.  If you are fasting, you can decide to end your fast at any time by eating.  Starvation is rarely a choice and is a horrible thing.    There are rare instances where people have decided to starve themselves, usually as a form of political protest.  A particularly gut-wrenching story of this is the case of Bobby Sands.    Sands was an Irish Republican imprisoned by the British in the early 1980s.  He began a hunger strike to protest the British.  For our purposes, several things are worthy of note.  One is that he was a soldier in the Provisional Irish Republican Army and thus a fit young man.  In other words, Sands wasn’t a fat ass.   His hunger strike lasted 66 days before he died of starvation.

Let’s contrast the tragic story of Bobby Sands with the happy tale of Scotsman  Angus Barbieri.  Old Angus was a true fat ass.  Being a Scotsman, he decided to do something about it in the most forceful way possible.  He decided to just not eat until he got skinny.  Angus didn’t eat for a whopping 382 days (he didn’t cheat by drinking sugary drinks either).  During that time, he lost 276 pounds.  The critical difference between Angus and Bobby was that Angus started out as a fat ass.

Angus began with a starting weight of 456 pounds, and he stopped fasting when he reached his goal weight of 180 pounds.  The takeaway is pretty simple: Your body stores fat to run on when there isn’t any food.  As long as you have fat to burn, you don’t have to eat.  Real, serious health complications arise only when fat stores run out.  Body fat’s purpose is to use as a source of energy.  If you want to get rid of it, you have to burn it (unless you want to get medical interventions to remove it).  You can’t empty the gas tank if you keep adding new gas!

The current wisdom of eating three meals, three snacks, and tons of sugary beverages is catastrophically stupid.  The more often you eat, the more you are likely to eat overall.  The more sugar you eat, the less able you are to burn fat.  If you eat low amounts of carbohydrates and do so infrequently, you have hit on a very powerful strategy for losing body fat.

One advantage of fasting is that it does not suffer from the limits of other diets.  You can’t become more vegan if your vegan diet isn’t working.  You can’t lower your carbs when you are already down to zero.  When nothing else works, fasting will work.  It is also free, convenient, and scalable.   Keto diets may be expensive, especially if you want to focus on high-quality meat.  Fasting means no shopping (it’s totally free), no clean-up, and no cooking.

Note what I didn’t say about safety.  There really isn’t a bar to fasting for any particular group of people not defined by medical concerns.  Women can benefit from fasting, as can older people.  Dr. Goldhamer has studied the effects of fasting on elderly populations, and he concludes that the safety concerns are no different than for younger people.

Mood and Fasting

Many people who consider fasting think they will be horribly hungry and “hangry” all the time.  This is more a myth perpetuated by candy bar commercials than anything else.  Clinical case studies by doctors reveal that most people report an elevated mood after the second day on a fasting schedule.  They start to feel great, as well as become more clear-headed.

One aspect of getting healthy that prevents many people from making a serious effort is what can be called a “hedonic calculus.”  We reason that food is fantastic, we love it, and we’d rather die young than live on tasteless cardboard.   One of the most interesting observations about fasting is that it reboots our sense of taste.  When we are addicted to sugar, salt, and oils, we need a lot of that stuff to feel satisfied.  As a kid, my grandmother described milk as either buttermilk or “sweet” milk.

I never understood that “sweet” reference.  After a protracted period on ketogenic diets interspersed with fasting, I learned what she was talking about; whole milk actually does have a sweet taste when you give your tastebuds a rest and let them start working correctly again.  When I started a ketogenic diet, my saving grace was bags of pork skins (chicharrones).  They were crispy and salty and very nearly replaced potato chips.  Now, the level of salt in those things is unbearable.  I no longer eat the bagged ones from the store regularly.

Tastes adapt over time when given a chance.  What you like and don’t like changes over time, and you can learn to like new things.  As a child, I found black coffee to be bitter and gross.  Today, I am an unrepentant coffee addict.  If you can adapt to like new things, why not encourage your pallet to like the things that aren’t making you fat and sick?  After a three-day or longer fast, pretty much any food will be pretty tasty.  That’s a good beginning to start liking new things.

Energy and Fasting

A popular misconception today is that if you don’t eat for a day, you’ll run out of energy and perhaps fall over dead.  A little thought suggests that this is ridiculous.  Our ancient ancestors would have fallen over dead so often that the human race wouldn’t have made it until today.  If you are sugar-addicted and haven’t burned fat in years, transitioning from burning glucose to burning fat will likely be rough.  But after the transition, you will start to feel energetic and clear-headed.  Dramatic drops in glucose do signal to the body that food is scarce.  What does that suggest your body should prepare to do?  The obvious answer is “go out and find food.”  The search for food requires energy and mental clarity.  As one would expect, that is precisely how the human body is designed.

You will note that you become wide-eyed and bushy-tailed in the fasted state.  In other words, you will become mentally alert.  People following a fasting plan report feeling more energetic and that aches and pains subside.  The clever reader may think, “ah, the placebo effect.”  That is possible, but another possible reason that painful joints and other discomforts go away is the reduction of inflammation in the body.  This can be tested via a standard blood test at your doctor’s office. The level of C-reactive protein (CRP) increases when there’s inflammation in your body.  Several practitioners have reported that this inflammatory marker came down during fasting.

Another explanation for enhanced energy during fasting is the basic survival benefits of that.  If I say “hungry wolf,” you immediately think of a very dangerous and capable predator.  Hunger drives the animal to search for food and makes it especially dangerous.  Humans, it turns out, have a very similar response.  Fasting causes the primal brain to go into hunting mode.  If we got lazy and sleepy when faced with hunger, our ancestors would have died out long ago.  We would not be here to have this conversation now.

The Microbiome

You may have noticed that probiotics are a popular health craze these days.  This isn’t totally snake oil.  The human body is really just a big bag of bacteria with legs; the bacteria outnumber the cells of your body ten to one. Fasting has positive effects on the microbiome.

When we eat high-fiber foods, the nutrients in food go further into the digestive system where the bacteria live, and they get more of it.  As the old saying suggests, pregnant women aren’t just eating for two; everyone is always eating for a hundred trillion.  This is one of the reasons you need to eat plenty of fiber if you are a fat ass.  Less energy makes it into your bloodstream when fiber is present.  This fact is another nail in the coffin of any way of eating that involves counting calories.  The idea that calories alone mean anything is just a bullshit myth.  Ignore the calorie math and pay attention to the science if you want to make any progress.

The simple takeaway for this topic is “feed the gut.”

Grades of Fasting

People usually need to “ease into” fasting to control hunger and feeling bad.  You can jump in, but it is often considered better to start slow and move into longer and longer periods of not eating.  First, eliminate snacks.  Go back to the 1970s (and forever before) practice of eating three meals daily.  Because of satiety issues, it is often better to eat a ketogenic diet (for a week, let’s say) before you start fasting.

Fasting is not a one size fits all proposition.   The most common type of fast is called an “intermittent fast,” also called “restricted feeding.”  The usual method of doing this is to extend your nightly fast from 8 hours to 16 hours.  How does one accomplish this?  Skip breakfast.  It’s that easy.  No special herbs, supplements, pills, or apps.  Just don’t eat breakfast.  Intermittent fasting is generally considered a safe practice that can be done by pretty much anybody.  The only people needing medical advice before attempting to alter their eating window are those on blood sugar-lowering drugs or other underlying medical conditions (see Dr. Fung’s book for a deeper discussion of these issues).

The other major type of fast is what is often referred to as a “long-term water fast.”  This is where you only consume water (some people will add coffee and tea to this) for multiple days.  It is always recommended that such fasts be conducted under medical supervision.   There are residential programs where you hang out for a month and don’t eat.  Your vitals and blood levels of critical nutrients are monitored.  The longer you are fasting, the more you will want to consider the need for medical supervision.  If you want to emulate Jesus and fast for forty days, please consult your doctor.

Longer-term fasts should be avoided by several types of people.  First, you need toe reserves to pull this off. If you aren’t fat and sick, it would be silly to endure a long-term fast.  There are contraindications such as kidney disease, heart disease, and drug safety issues.   Most of us fat, sick people (that aren’t too sick) can see some real benefits from long-term fasts.  Why do this?  The short answer is that the body will heal if we get out of the way and quit poisoning it for a while.

No matter your ultimate goal, it is best to ease into fasting.

First, cut out all of the sugars long before you plan to fast.  Withdrawing from sugar and being hungry at the same time may well make you feel terrible.  Also, get rid of all processed foods.  Get rid of it if it has a bar code or comes as a powder.  Eat whole foods.  Get rid of all the bread, bagels, muffins, tortillas, and other bready things.  Get rid of all the stuff in boxes and bags (those have bar codes).

Once you’ve started eating a whole foods diet, you can begin to skip meals.   You can do this randomly.  For a couple of weeks, only eat two meals within six hours of each other.  For example, have lunch at noon, then dinner before 6:00 PM.  After you’ve learned you can skip some meals and you realize you won’t die, you can move to one meal a day (OMAD).

If you want a more powerful fast still, you can transition to fasting all day, one or more days per week.  For example, many religious people may choose not to eat on the Sabbath.

Longer Fasts

As long as you are not malnourished, there really isn’t a limit to how long you can fast.

Many people choose to engage in 36 to 48-hour fasts, also known as alternate-day fasting.  These longer fasts have some distinct advantages.  First, no matter how much glucose you’ve crammed into your body, after 36 hours, you will likely be in some degree of ketogenesis.  Of course, some of us want to know when we are in ketosis.  That is no problem if you are willing to pay for some “keto sticks.”  These little strips of plastic have a coating on the end, and you urinate on that.  The little square of the coating changes color based on the level of ketones.  Compare it to the color chart on the side of the container, and you know your level of ketones.

The presence of ketones means that you are burning fat and getting some of the significant benefits of fasting.  There is some autophagy, and growth hormone levels are picking up.  BDNF production is increasing.  This success can be a powerful psychological motivator for some of us.

Perhaps the most prescribed extended fast is the three-day water fast.  That means you consume nothing but water (and any medications) for a full three days.   Almost all of the advantages of fasting have started by this point.  Working your way up to this length of fast is highly recommended.  You will likely feel sick if you go from massive amounts of sugar to a lengthy fast.  You feel terrible and achy while your body is adapting to burning fat. This will be nearly identical to what many call the “keto flu.”   Such extended fasts are often recommended for restarting weight loss once a plateau has been reached.

Dr. Alan Goldhamer of TrueNorth Health is a big advocate of long-term “water” fasts.  The water fast is the strictest form of fast, where you only consume water for the duration of the fast.  There is no tea, coffee, or bone broth.  He has fasted thousands of patients and reports some fantastic results in improving health markers associated with metabolic syndrome.

He is quick to point out that with long-term fasts, there is the danger of “refeeding syndrome,” which can be dangerous.  He has developed a strict “refeeding protocol” that he follows with all his patients.  Dr. Fung also discusses this issue and describes how to reintroduce food after a long fast.

Body scans showing body composition show that fasting people lose about a pound daily.  A lot of that loss is fiber, glycogen, and water.  The enduring loss, however, is primarily visceral fat.  That is the nasty fat around your organs that shouldn’t be there; visceral fat is the stuff that makes you really sick and threatens your life.  There is very little loss of muscle tissue.  This suggests that the weight lost during a fast may not be as dramatic from a numerical standpoint but can be truly dramatic from an overall health perspective.

I say little muscle loss, but there is some, and it is muscle loss you want to see.  Logic and practical experience tell us that you put on muscle when (and only when) you strain your muscles by working against resistance.   If you are 400 lbs and still moderately active, you have leg muscles (quads and calves) that powerlifters would envy.  (If you doubt this, wander onto a college campus and find a fat guy in the marching band, then check out his calves).   Think about it; you are powerlifting that 400 lbs of ass all day, every day.  You can develop some huge muscles that way.

As you drop weight, you no longer need to burn calories to feed all that extra fat and muscle tissue, so your basal metabolic requirements will fall.   In addition, your muscles will shrink because you are reducing the amount of weight they are moving around on a daily basis.  That, my friend, is an excellent thing.  There is no evidence that fasting (unlike starvation) causes any significant reduction in cardiac muscle size, and we know that the function is improved.  To discuss this may seem like an appeal to vanity, but it is much more.  Lower body fat and lessened strain on the cardiovascular system are excellent for overall health and longevity.

Mixed Methods

The real benefits of fasting only show up when you’ve burned up all of the sugar in the blood, as well as all of the stored glycogen.  One way to shorten the time it takes these benefits to start is to maintain a low blood sugar level all the time.  That way, the benefits accrue much faster when you start a fast.  An all-day fast on Monday would do little good if you gorged on donuts and Cheetos on Sunday.   If you eat a low carbohydrate diet consisting of whole foods all of the time, then fasting becomes far more powerful.

References and Further Reading

I’ve added a complete reference page to my book on this site.  I’ve also included “further reading” articles in books on this site, organized by the book chapter headings.  Book links to Amazon are affiliate links, and if you happen to buy something via one of those links, I get a small kickback from Amazon to help keep this site up and running.  Thank you for your support!

In an interview with Dr. Rangan Chatterjee, Dr. Jamnadas talks about the benefits of fasting that he actually observed in his own patients.  Remember that he is talking about real sick people, not theoretical conjecture in a biochemistry textbook.  That video is linked below:

Dr. Jason Fung’s basic “how to fast” video is linked below:

For a deep dive into EVERYTHING about how to fast, check out Dr. Fung’s popular book:


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Last Modified: 01/06/2023


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