In many societies, fasting is a common practice. While it is usually a religious-based practice, it can also be a cultural one. Fasting for health reasons has been done for many centuries, going at least back to the Greek physician Hippocrates who would recommend fasting for certain illnesses, yet to this day it is not broadly accepted as a health practice. That’s probably because it isn’t popular with patients, particularly in Western cultures where food is plentiful and indulgence is usually practiced over fasting.
It also may not be all that popular because it has drawbacks. Water-only fasting quickly drops the “food load” — the digestion and detoxification energy that accompanies having food in one’s system — to nearly zero. That’s a big bonus. But it also means no nutrients are coming in, which the body requires. So fasting isn’t sustainable. Plus, even for short fasts, the body will complain about the lack of food, trying to prompt you to go out and get some.
Religious fasting was considered to be honoring to God by putting off the bodily desires, which were distractions from focusing attention on God. Even non-religious society recognizes that giving in to all bodily desires is actually harmful, because some of those desires feel good at the time but are uncivil behavior. Everyone recognizes that orderly and partially restrained behavior is the only way to live. Giving in to all passions and desires results in primal behavior, and restraint is only civil. And bodily passions aren’t always healthy — the body is sometimes not the best determiner of what it really needs.
Fasting can be confusing — it has value but also drawbacks. When and how to deny food cravings and hunger to improve health requires knowledge. Simply giving in to them is a formula for disaster, but uninformed fasting can also be harmful.
Life in the Fast Lane…
Ideally, we want the advantages of fasting without the drawbacks. The first step is recognizing that indulgence, the opposite of fasting, is a road to disease. At the very least it is a path to obesity, but when we combine a lack of true nutrients with calories and taste appeal, as happens with modern highly processed food, it is a path to disease. So the first step is to break the acceptance of the standard American diet along with all the standard American snacks.
Food cravings are more complicated. These may be harder to ignore than simple hunger. When you have food cravings, your brain is signaling a need for something, but that something may not be what you interpret it to be. Often you may think you need more food, when you actually need water. Cravings are part of your brain and body telegraphing a need, but those signals may be confusing. When you are stressed, your body produces the hormone cortisol, which increases blood sugar levels and can make you crave food, when what you really need is to relax. The cravings do indicate a need, but the need is easily misinterpreted. Simply ignoring the cravings also ignores the need, and requires constant exercise of willpower which often wears down your resolve and eventually fails.
What happens when you fast? First, your body utilizes the glycogen stores in the liver (primarily) and skeletal muscle, through a process known as glycolysis. Glycogen is basically some glucose molecules stuck together in a convenient manner for storage, and it can easily be turned to glucose to keep your blood sugar levels steady — until it is depleted, which happens in about 24 to 36 hours after starting a fast, depending upon your metabolism during that time. Before that, even though your metabolism has not run out of this relatively “easy” energy supply, you are still getting benefits during this period of fasting. The main benefit is taking a vacation from insulin, because as your blood sugar starts to drop since you are fasting, insulin shuts off and instead your body produces glucagon, which tells your liver to turn its stored glycogen into glucose. Such insulin vacations are vital to preventing your body from getting tired of responding to insulin that could lead to insulin resistance and finally diabetes. Giving your body plenty of insulin vacations is a great way to keep type 2 diabetes at bay. Further, sugar is a great age-promoting factor, so not having long periods of insulin production reduces wear and tear of your body and thus increases longevity.
After the 24+ hours, the easy food source is gone, and glucose levels still need to be maintained, so your body turns to the other two types of food: proteins and fat. Since you are fasting, these must come from internal sources. Most of us are happy about sacrificing the fat, but we are not so excited about catabolizing protein, which we fear we would lose from muscle mass. This isn’t nearly the problem that you’ve probably been led to believe by the typical hype. After glycolysis has halted because the glycogen stores are depleted, your body will enter a period of gluconeogenesis, where it will produce glucose from amino acids, which it gets from protein in your body, including muscle mass. Well, not all the protein in your body is in your muscles. At any time when your body is searching for protein when you are fasting, the process of autophagy activates, where your body painstakingly searches everywhere for defective proteins that have built up in all your tissues and organs. Autophagy isn’t fast enough to supply all the gluconeogenesis protein needs, but it helps, and you are also cleaning up your body at the same time. So should you be worried about losing muscle mass to fasting?
Fat chance
Your body wasn’t designed to catabolize muscle as a primary energy source. Fat is a much better energy store as it is much more energy packed than protein. The only reason there is some protein breakdown with fasting beyond the glycolysis window is the switchover period to full fat burning is generally a little slower to meet all your needs. But the main reason you have fat is to store energy, and it is the number one choice of your body for energy retrieval. Fat is there for burning when you need it.
Let’s say you have a whole house solar powered battery backup system designed to power your house for a couple of days if needed. You’ve got your battery charged up to full and a huge storm knocks out your power. Would you ignore your battery system and go fire up your little gasoline powered generator? You could do that, but why? You would use the backup system because it was designed for this very situation. Your body stores fat for times when it’s needed, particularly when fasting. Triglycerides are broken into free fatty acids and glycerol that the liver, through ketogenesis, converts into ketone bodies (mostly) and glucose (small amount). Your body, including your brain, use these ketones for energy. Most all tissues can convert the ketone bodies into acetyl-CoA, putting it back into the energy-producing citric acid (Krebs) cycle. Thus fat can sustain your body even during long fasts — it contains all the basics. It’s the ideal energy backup system, and it’s so efficient that one pound of fat can fuel your body for a day or more. That may not be good news for those of you hoping to lose many pounds of fat per day on a diet or a fast — your body just won’t need it that rapidly.
OK, we have now moved in to the long term stage of fasting, where your body is burning fat almost exclusively to sustain itself. The gluconeogenesis phase is short-lived as your body settles in for the long haul with fat. It had to first get into fat burning mode, so protein helped out for a short period. Your body is not relying on insulin, so you get an extended insulin vacation; you are scrounging defective proteins throughout your body; you are burning and thus reducing triglycerides which are known to promote cardiovascular disease in high quantities; you are reducing inflammation; and yes, you are shedding pounds. The process is explained in detail in a review study published in Cell Metabolism, where researchers compile results from numerous studies regarding animal and human reactions to fasting. They point out something particularly unexpected: all mammals become active when hungry and and sedentary when satiated. (1) You might expect the opposite: when all fueled up, you would expect to have more energy, and when running out of fuel, you would expect to need to conserve what energy remains. Actually, when fasting for even a few days, you are nowhere near running out of available energy — your body just has to work to go get it from your fat stores. This review study shows that fasting is anti-cancer, anti-inflammation, strengthens the immune system, improves brain function, and generally enhances health.
Fast the slow way
Fasting is highly beneficial when you are burning your own fat, especially if you have plenty to burn, but you would like to get your body so good at jumping into fat burning mode that you don’t go through much interim protein burning. When you are burning fat at sufficient levels to fuel your body fully, it will leave the protein stores alone. If you eat fat in sufficient quantities so your body must rely on dietary fat to get sufficient energy, you are exercising the fat burning mechanism. So the way to teach your body to burn fat efficiently is to train it to do so, even when not fasting.
In a study published in Nature Communications, researchers from the University of Southern California conducted human trials where the participants ate a largely plant-based diet of high fat, low in protein and sugar. They merely ate the special diet 5 out of 30 days, then ate their normal diet, over a few months. Simply this amount of special dieting was enough for the participants to show lower diabetes risk factors — including less insulin resistance and lower A1C levels, reduction of body fat and liver fat, and an increased lymphoid-to-myeloid ratio, which indicates a more “youthful” immune system. They also cited previous research where such dieting promoted stem cell regeneration and reduced signs of dementia. (2)
In essence, the study showed that someone can get the major benefits of fasting without actually fasting. They avoided the type of fat (saturated) that appears in animal meat, and also cut out most protein — meaning that a plant diet of avocados, seeds and nuts for fat and raw vegetables for low sugar carbohydrates is an ideal permanent fast. Such a diet is a whole diet though, so there’s no reason to eat otherwise. Putting all this together: eating a raw plant diet gives you all your nutrients (better than any other diet) while giving you fasting benefits.
But there is another consideration. Most of us simply eat too much and too often to even approach the benefits of fasting. Not eating for 14 or more hours, which you can easily do with an early supper and late breakfast, gives your body a break from “food load” and insulin. Eating and drinking junk, especially sugar, throughout the day keeps piling on inflammation-promoting, fat storing, and energy-draining food load. Even healthy snacks are not helpful if you don’t give your gut a nice break from the constant influx of food.
Unless you’re actually under weight, you probably just don’t need as much food as you think you do. If the scale or your body mass index shows you have more fat than you should, you definitely don’t need as much.
Finally, don’t coddle your body. It’s easy to misread the signals it gives you. If you come home tired from an exhausting day of work, with meetings and computer work keeping you at your desk for the day, are you misreading what your body needs if you go sit in front of a TV for the evening? Of course you are: you don’t need physical rest which you’ve had all day, but physical exercise. Likewise, if you are getting food cravings, you probably don’t need more food — you need to deal with the stress, the habits you’ve formed, and your probable deficit of real nutrients instead. You have a brain so you can use it and realize what you actually need, rather than just giving in to what you feel like doing. Those cultures that fast consider it to be a virtue, because denying body desires when appropriate is something animals don’t understand, and we consider ourselves higher than animals. Appropriate self-denial, if done for the right reasons and with knowledge, is a virtue, a discipline, and very healthful.
Ageless Advice
Eating less is key. Eating the right foods is also key. You can live a life of fasting both through eating and not eating: eating well when you do eat, and giving plenty of time between meals. Aging is a chronological process, to be sure, but the effects of aging are what we largely do to ourselves. Food is a large part of the reason we age ourselves. Don’t gum up your system with unnecessary food. Shun harmful food. Then you can age the way you were designed to: slowly, mostly disease free, and with energy and vitality for many more years than the average person. Eat less.
Dr. Nemec’s Review
What is fasting? It’s denying the mind its pleasures.
Why is this a good thing? First because those pleasures were created in early childhood by upbringing and by created addictions to foods that were not health promoting. Take sugar, for example: most every young child gets some type of sugar as a treat — even a reward for being or doing good. This sugar causes imbalance in the neurotransmitters in the brain, and neurotransmitter imbalance it is the root cause of addictions.
So fasting is first and foremost denying the mind the pleasures that will not only in the long run ruin your brain, but also destroy your body with premature aging and disease production.
Secondly, fasting is also denying your body, which as the research has shown gives it a break to reset, rebalance, and do some house cleaning internally. This is why fasting is a key in longevity.
Look at your metabolism like a generator. Generators kick on when they’re needed and then shut off when they’re not needed. The generator’s wear and tear is calculated by the number of hours it runs, so if your back-up generator ran 24 hours a day, it will need service more frequently and it’s service life will decrease. Generators are not meant to run all the time, but just when needed.
Your body’s metabolism is a generator, and like a generator it will last longer the less you run it. So in this analogy when are you running the generator? Every time you eat, because every time you eat that food has to be processed, metabolized, and burned for energy. When you burn things for energy, that produces byproducts and waste products that are inflammatory and wearing on the body. So common sense says: burn less often and the generator will last much longer.
According to the Cell Metabolism article, fasting is anti-cancer, anti-inflammation, strengthens the immune system, improves brain function, and generally enhances health.
According to the Nature article, this modified plant-based diet form of fasting has been estimated to delay the aging process by seven years — this could cut mortality from age-related diseases in half at nearly every age. This calculates to a 20% slowing of the aging process because health is being maintained. This could save over $7 trillion of health and pharmaceutical costs over the next 50 years.
All this can be achieved by just eating a living, raw, plant-based, high plant fat diet, and eating within a time window of 10 hours a day. Do you understand the power of this statement? By eating a plant-based diet in the restricted time of 10 hours you can cut dying from disease in half at every age and you can save a bankrupt nation from unnecessary spending.
This is not difficult to do. You are not really going without. You’re just eating different foods, more health-promoting foods, more anti-inflammatory foods, and more anti-aging foods — and you may eat as much as you like as long as the it’s the right type of food. Also it’s not difficult to eat in a 10-hour time window: most everyone can do this without much distress.
So water fasting is the most drastic fasting and can only be done periodically. It cannot be done usually in one’s normal activities of daily living, whereas with this plant-based high fat diet, food quantities are not limited. It is really not a fast at all, but really just a fast from the standard American diet.
By eating a plant-based high plant fat diet, you decrease your risk greatly of all diseases and you increase your life substantially — and basically you’re not really fasting. You’re just eating healthier food, eating food the way you were designed to eat in the beginning.
“I give you every seed-bearing plant on the face of the whole earth and every tree that has fruit with seed in it. They will be yours for food. And to…everything that has the breath of life in it—I give every green plant for food.”
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(1) Sanvictores T, Casale J, Huecker MR. Physiology, Fasting. [Updated 2023 Jul 24]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK534877/
(2) Longo, Valter D, and Mark P Mattson. “Fasting: molecular mechanisms and clinical applications.” Cell metabolism vol. 19,2 (2014): 181-92. doi:10.1016/j.cmet.2013.12.008, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3946160/
(3) Sebastian Brandhorst, Morgan E. Levine, Min Wei, Mahshid Shelehchi, Todd E. Morgan, Krishna S. Nayak, Tanya Dorff, Kurt Hong, Eileen M. Crimmins, Pinchas Cohen, Valter D. Longo. Fasting-mimicking diet causes hepatic and blood markers changes indicating reduced biological age and disease risk. Nature Communications, 2024; 15 (1) DOI: 10.1038/s41467-024-45260-9
