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All About Intermittent Fasting (IF)


Intermittent fasting… you must have heard about it… and you must be asking what in the world is it? And you might also be wondering if you will get something good out of it or not. Right?


In a previous article, we talked about what the low carbohydrate ketogenic diet is and its potential benefits especially in relation to insulin resistance, type 2 diabetes, hypertension and the overall Metabolic Syndrome. Then a patient asked me: What about intermittent fasting? Does it have a beneficial role towards metabolic health? In this topic, let’s talk about it!




Fasting is not a new concept. Human beings from various civilizations throughout history have been doing fasting for so long - whether it be by necessity because of food scarcity, or for some religious reasons perhaps related to "purification" of the soul, such as that being done by Muslims on Ramadan or Christians during the Lenten season. Even Buddhists do fasting on a regular basis!


We know that our cavemen hunter-gatherer human ancestors had to fast by necessity in between periods of hunting and gathering. At that time, they simply had no way of preserving their food. So for them, it’s an alternate period of fasting and feasting. We also know that animals who hibernate, technically, are fasting for the entire winter! They have to store sufficient fat in their bodies to last the whole winter, lest they fail to survive, and they do this by eating fruits during autumn.


Indeed, the capacity to fast has been hardwired into our genetics. The ancient Greeks thought of fasting as some kind of panacea or cure-all to many illnesses. Hippocrates prescribed it during ancient Greek times, and even Plato and Aristotle were among its staunch supporters!




So, what about "intermittent fasting"? The current concept of "intermittent fasting" or IF, is all about incorporating a certain period of "fasting" into your daily or weekly eating routine, on an intermittent basis. It is otherwise called “time restricted feeding” or TRF. The idea behind this is to strictly limit your eating hours or "eating window" within a strict time frame, beyond which you are not supposed to consume any calorie-containing food or drink.


We all have most probably already experienced fasting for something like 12hrs, especially when we finish eating at say, perhaps around 7 o’clock in the evening, until that time we eat again at around 7 o’clock the following morning after sleeping overnight. That’s the reason why our vocabulary and our culture has customarily called that first meal we have for the day as “breakfast” – precisely because we are breaking our overnight fast!


In a nutshell, the focus of "intermittent fasting" is WHEN you eat, and not much of WHAT you eat. Because if you have to follow "intermittent fasting," there is only a specific time that you are supposed to eat - either for a certain number hours on a daily basis, or eating only on certain predetermined days of the week.


If we have to stick to a strict definition of what "intermittent fasting" is supposed to be, then we probably wouldn't have to be talking about what particular kinds of food to eat during the “eating window.” However, if we intend to optimize the use of "intermittent fasting" towards augmenting the "reversal" of the so-called "insulin resistance," which many people more commonly know of in its advanced form called Type 2 diabetes, then I will have to share with you my own personal science-based recommendations on how to do it and apply it in your own circumstance: which means you have to stick to a low carbohydrate diet!


And if you have to ingest carbs – I insist that you eat only the whole-food kinds of carbs which are usually fiber-rich, such as leafy above-ground vegetables and certain healthy low carb fruits like avocadoes and berries, and as much as possible, never ever the refined and highly processed ones – mostly consisting of sugar, foods containing high fructose corn syrup (HFCS), flour, refined grains, and other starchy foods. More about that later.


I already made a video about my own personal testimony with regards to how I reversed my own Metabolic Syndrome using the very low carbohydrate ketogenic diet (VLCKD). I’m linking that video here and do find time to watch it! In between my low carb diet, I actually did some episodes of intermittent fasting.




The most important objective of therapeutic fasting is to avoid triggering the production of high insulin levels in your bloodstream. When you DON’T put anything into your mouth that could potentially trigger this insulin response, then it naturally follows that your insulin will stay low. Not taking in at all any form of macronutrient – which is precisely what IS called FASTING – is better able to avoid this insulin response. In a previous video, I showed you how different macronutrients elicit their own unique insulin response, with carbohydrates promoting the highest levels of insulin, as compared to protein and fats. Of course, carbs, especially simple sugars, are the most notorious for elevating insulin.


While on your strict fasting window, you may have non-caloric substances such as water, pure black coffee or tea, and they should have no added sweeteners or fat like cream.




But is FASTING any different from STARVATION? Somebody once asked me that. Well, in context, indeed there is a difference between the two. When you are STARVING, or if you are being STARVED, that means the absence of your food is not within your control. You are NOT voluntarily keeping food away from yourself. On the other hand, when you are FASTING, you are withholding food on a deliberate basis – whether for your health, for fasting of a spiritual or meditative nature, or perhaps some other reasons.




How do our bodies respond when subjected to starvation and fasting? Among the first scientific studies on the body’s response to fasting were done by Drs. George Cahill and Oliver Owen. The metabolism of the brain during fasting was particularly presented in this paper published in the Journal of Clinical Investigation last 1967, where Owen was the first author.


It was found out that during starvation, glucose is replaced by ketones, especially β-hydroxybutyrate and acetoacetate as primary fuel in the brain. As shown in this graph provided in the study, the transition from the fed state to the fasted state occurs in FIVE PHASES.


Shortly after feeding (which is PHASE 1), glucose coming in from ingested food is initially used as primary fuel by the body. As the levels of exogenous glucose start going down after 3-6 hours in the post-absorptive phase (PHASE 2), glycogen stores from the liver are slowly broken down through glycogenolysis in order to provide additional glucose to the bloodstream. This continues approximately for the next 6-24 hours after fasting. Thereafter, once the glycogen stores of the liver begin to get depleted, gluconeogenesis kicks in (PHASE 3). Glucose may be synthesized in the liver from non-hexose precursors, such as the glycerol backbone of triglycerides as well as certain glucogenic amino acids such as Alanine, Glycine, Arginine and a couple of others. Lactate and propionate may also be converted to glucose. This process is called gluconeogenesis, and occurs in the liver and the kidneys.


After a more prolonged fasting time occurring more or less 2-3 days since last food intake, the levels of ketone bodies begin to go up (PHASE 4) and it eventually becomes a major fuel for the brain. By then, a person is in the phase of "nutritional ketosis," wherein ketone bodies, mainly beta-hydroxybutyrate and acetoacetate, are produced from fatty acids in the liver.


With low levels of insulin, fat stores in the adipose tissue are broken down for energy consumption into free fatty acids in the process called lipolysis. Fatty acids are used as fuel by many tissues in the body. But the brain cannot utilize them since they cannot cross the blood-brain barrier. Ketone bodies, however, can cross the blood-brain barrier, thus they become the major fuel of the brain at this phase. After about five days of fasting, human growth hormone (HGH) is kept at higher levels, and this maintains the mass of the muscles and lean tissues. This is noted as the Protein Conservation Phase (PHASE 5). At this phase, the body burns fat easily, and the basal metabolic rate (BMR) or basal energy expenditure (BEE) is mostly provided by free fatty acids and ketones. Adequate levels of metabolism are maintained by relatively higher levels of adrenaline, and the basal metabolic rate is kept at a steady state. Muscle wasting, as an effort of the body to feed itself, does not occur until all of the body’s fat stores are consumed.


Interestingly, it is worth noting that a low carbohydrate ketogenic diet regimen mimics these effects of fasting, and thus, in a ketogenic diet, the fat-metabolizing state of nutritional ketosis is maintained.




There are a number of ways of doing “Intermittent Fasting.” These fasting periods may last anywhere between 12 to 40 hours, and among the most common would include: Alternate-Day Fasting, the 5:2 Diet, the Eat-Stop-Eat Method, the One-Meal-A-Day or OMAD Diet, and the 16:8 Diet.


On an Alternate-Day Fasting, you fast for a 24-hour period, followed by 24 hours of unrestricted eating, and you do this on an every-other-day basis.


In the 5:2 Diet, you get to choose any two 24-hour periods to fast within a week. Usually, those days are spaced away from each other. The remaining 5 days of the week may be spent eating without restriction.


In the Eat-Stop-Eat Method, you get to choose one day per week of a 24-hour fasting period.


The OMAD Style, which stands for One-Meal-A-Day, is done by eating one full meal a day. This could be a 20:4 or 22:2 eating and fasting window, wherein you eat your one meal within a 2- to 4-hour window, such as when you just eat a full meal at dinnertime, and the rest of the day you may drink only water, tea or black coffee.


Lastly, the 16:8 Fasting Method is perhaps the most common and may indeed be among the easiest to follow. You fast for 16 hours straight, followed by an 8-hour eating window. This may be done when you wrap up your dinner by 8pm, take nothing that contains calories afterwards, and do fasting overnight which of course includes your sleeping time, and then break your fast the following day at noontime. In this case, the 16-hour fasting period is from 8 in the evening until noontime the following day, and the 8-hour eating window is from noontime until 8pm.




Intermittent fasting has several established benefits for your overall health. At the molecular level, it changes the levels of certain hormones.


Due to a persistent drop in insulin and an increase in the levels of human growth hormone (HGH), intermittent fasting may help you burn visceral fat and lose weight. With avoidance of recurrent hyperinsulinemia, the same mechanism can reduce your insulin resistance, thus lowering your risk for developing full-blown type 2 diabetes.


Autophagy is an important cellular repair mechanism that gets initiated and reinforced with intermittent fasting, aside from the very low carbohydrate ketogenic diet (VLCKD). Autophagy is the process wherein cellular waste products in the form of broken and dysfunctional proteins that have built up inside the cells through time are removed. This was first discovered by the Japanese Dr. Yoshinori Ohsumi, for which he was awarded the Nobel Prize for Physiology or Medicine last 2016.


Enhancement of autophagy may provide added protection against neurodegenerative disease like Alzheimer's disease, as well as cancer. This amazing cellular waste removal mechanism called autophagy is worth talking about entirely in another video.




Overall, Intermittent Fasting is considered safe. However, disciplined caloric restriction, as what happens in fasting, should be best done with caution in certain groups of people, including the following:




Can Intermittent Fasting and the low carb ketogenic diet go well together? This topic indeed deserves another video of its own. But based on established studies, as well as my own professional and personal experience, I would highly recommend doing intermittent fasting together with a low carbohydrate diet. Doing so would make you better able to comply with the demands of intermittent fasting, since the presence of more fats and proteins in a low carbohydrate diet can lead to better and more prolonged levels of satiety.


If you want your insulin levels to remain low when you break your fast and enter your eating window, strive to keep yourself on low carb foods. If you eat more carbohydrates in your diet, your blood glucose and insulin levels rise. The more carbs you consume, the more glucose enters your bloodstream. Once insulin drives down your glucose levels, your body would send its signals to look for more nutrients, and you'd get hungry again faster and much earlier.


You can do intermittent fasting as often and as intermittently as you would like. But if you would like to optimize the benefits of “intermittent fasting” for your metabolic health, especially if you are trying to effectively address your obesity, type 2 diabetes and metabolic syndrome in general, a medically-managed therapeutic low carbohydrate diet (which could be in the form of a well-formulated ketogenic diet) done in conjunction with Intermittent Fasting, should work best to your advantage. Both the therapeutic low carbohydrate diet and intermittent fasting can be synergistic in keeping you within appropriate levels of nutritional ketosis. When you do so, it would be best if you also have certain of your blood tests monitored by your physician, as well as your body weight pattern, so as to keep them within acceptable levels.




           So, in brief: YES, for most people, intermittent fasting works! And if you intend to use intermittent fasting to specifically address your metabolic health, the more it would work best to your advantage if you also do it together with a low carbohydrate diet (LCD) regimen.


           I hope you get to learn much from the things we have discussed here. Like the YouTube video above and share it with your friends! Don't forget to subscribe to my Low Carb Health Doctor | LCHD channel! To get notified of upcoming videos, hit that notification bell! And see you in my next video!