5. Fasting: An introduction

I’d like to tackle a topic that may sometimes cause some confusion among persons who would like to pursue an optimum state of health. Way back in article 3 (Nutrition for Weight Loss) I had made a comparison between the paleolithic human versus the modern day human. Here, I had highlighted that there were two forms of fuels which the body uses to burn energy - sugar (carbs) and fat. I had even attempted to make the jump myself from my lifestyle as a modern day human towards a (metaphorical) paleolithic human. I had made this comparison because way back then, life was much simpler. The foods we consumed were the foods we hunted for (using intense physical activity). The foods we consumed were natural foods (grass-fed herbivores with zero added hormones and/or antibiotics). We also ate solely when we were hungry (meaning that intermittently, we fasted and sometimes dealt with famine). Moreover, our bodies, being the beautiful, well-oiled machines they were and still are, are capable of catering for a failed hunt - which strictly speaking happened more often than not in the distant past.

Now-a-days modern bro science created the concept of 3-4 hourly feeds. You may have heard this recommendation from your friendly neighborhood layman or gym professor. This concept became popular because with an ideology centered around building muscle, we tend to oppose the elusive state of catabolism (breakdown of body tissue), that occurs in the absence of food. Many of us long for a state of continual anabolism (synthesis of body tissue) because it “makes us buff”.

I want to start by defining two key terms: starving and fasting.

  1. starving = not meeting your daily calorie needs (i.e. consuming less calories than your body needs to maintain basic bodily functions and in doing so… survive)

  2. fasting = creating a window where there is zero consumption of calories and antagonistically creating another window where there is considerable consumption of calories

The principle health differences between them is that the former can lead to weight loss and ill health (if not death), whereas the latter can lead to weight loss, healthy weight maintenance and longevity. Principally, the concept associated with the health benefits of fasting are due to the body’s inherent ability to categorize what it needs and what it doesn’t need. The human species took part in fasting for centuries upon centuries, throughout times where historically obesity was not common. Hippocrates, the father of medicine even cured persons from ailments simply though fasting, stating that ‘feeding oneself whilst ill is feeding the illness’. At some stage though, the introduction of intensive snack marketing, particularly of non-nutrient dense snacks (refer to article 4) rendered fasting among society as a rare approach to health. Therefore, despite the fact that perhaps you can argue that in the past (1900s - 1950s) individuals did have unhealthy meals - this mentality was not the social norm. People ate breakfast, lunch and dinner, sometimes even less in times of famine or depression, and that created a period of fasting. In any case, just to break your bro science mentality from now, there is no evidence that supports ‘snacking’ in between meals for any outcome deemed a ‘health benefit’. None whatsoever.

A study by Catenacci et al. (2016) compared zero calorie alternate day FASTING to a DAILY CALORIE RESTRICTION in two groups obese adults. This protocol lasted 8 weeks and a follow up was conducted for up to 24 weeks after the protocol was concluded. The fasting group displayed better results in almost every marker examined, most notably in body fat percentage (BFP), lean body mass and weight regain. The group undergoing daily caloric restriction ended up gaining the weight back whilst the fasting group sustained the weight loss.

Fat loss. Time and again (as I highlighted in article 3), the best way to become fat adapted is to consume large quantities of fat and very small (if any) quantities of carbohydrate. Logically speaking however, if we were to not consume anything, this would be an even quicker way to achieve ketosis. Why? Because the body can just carry on burning it’s own internal stores of fat. There is no influx of food, especially carbohydrate, present in order to stunt this process. During fasting, there is no sugar in the bloodstream. Therefore, there is no secretion of insulin (which is needed to store the sugar). In addition, fats, which are stored as triglycerides (i.e. fatty acids and glycerol) can have their glycerol sub-unit broken down burned and used as glucose (gluconeogenesis). This metabolic process heavily supports the philosophy, therefore, that carbohydrates aren’t, in fact, needed by the human body. Not as a major macro-nutrient anyway.

Why is reducing calories unhealthy and why is fasting healthy?

In my opinion, the body can be accurately described by two adjectives. Complicated and efficient. Logically, yes - it makes sense that consuming less calories than you need per day will make you lose weight, and more often than not you will. However, the more complicated element people tend to overlook is that of the role of hormones. Hormones literally run the show, biologically. For every metabolic process, you have hormones which work antagonistically with each other to operate effectively and harmoniously. To give you a couple of examples:

  • Insulin is secreted when there is a rise in blood sugar (to bring down the levels of blood sugar) whereas glucagon is secreted when there is a fall in blood sugar (to bring up the levels of blood sugar).

  • Ghrelin is present when you are hungry, allowing you to feel hunger. You then consume a meal and start having leptin present which makes you feel full.

Now that this is understood (these are only 2 examples), remember: all your hormones are produced in fat. Thus, in the dire absence of fat (as found in persons who attempt to lose weight by eating chicken, rice and broccoli only - for two months), the body begins to store its remaining internal fat as aggressively as possible. Therefore, this kind of practice can literally make you feel weaker and in addition, may dangerously spike your cholesterol levels.

In addition to the fasting versus caloric deficit debate, another important factor to reflect on is that of the basal metabolic rate (BMR) which is defined as the rate at which your body uses energy at rest in order to maintain vital functions. During a prolonged caloric restriction, the body determines that there is a scarcity of food and begins to shut down several metabolic processes which it ‘perceives’ it can do without in such scarcity. Thus, although you may reduce your weight in the short term, you will reach a plateau. The BMR decreases as weight decreases and once the calorie intake is restored, your weight will inevitably up again, creating this ‘bounce back’ effect. This effect is augmented when there is a 2-3 hourly feed (as recommended by many bro scientists). In fact, this rationale is probably why persons in the ‘daily caloric restriction group’ during the Catenacci et al. (2016) study ended up regaining the weight they lost during the study.

Fasting does not affect your BMR - rather, it allows you to lose fat WHILST maintaining your BMR, because you are still consuming your daily calorie requirement. In addition, you have increased activity of 2 key hormones:

  • noradrenaline; which will promote fat oxidation and maintain BMR status

  • human growth hormone (HGH); which will promote the metabolic processes of newly ingested nutrients directly repairing and replenishing muscle tissue and will be significant on muscle growth (i.e you build muscle)

Hormone Activity

  • Human Growth Hormone (HGH): this hormone functions to stimulate growth, cell reproduction and cellular regeneration. It stimulates production of IGF-1, which is a molecule which mimics insulin and is involved in several mammalian anabolic (tissue building) effects. Especially within this context, it will increase the availability and utility of fats for fuel (Fung, 2016) whilst preserving internal muscle mass (and bone density). Without HGH, it is impossible to achieve the cellular renewal cycle.

  • Noradrenaline: the presence of this chemical is lowest during sleep and highest during activity (especially those of high stress). During fasting, the increase in noradrenaline is carried out, rendering us able to ‘hunt for more food’ which can explain why occasionally, persons who are in a fasted state tend to feel more energized and are sometimes unable to even sleep. Following a 2 day fast, there is an increase in BMR (as opposed to a metabolic ‘shut down’ perceived by most layman thought).

Autophagy and Apoptosis

Through fasting, the body undergoes increased autophagy, literally translating to “eating itself” (not a bad thing). Through autophagy, all aged and malfunctioning cells or organelles are broken down and removed, and useful energy is no longer directed to sustaining them. Apoptosis (which is programmed cell death), on the other hand, refers to the end of life of a cell, which is killed after it has replicated a certain amount of times (achieving its biological purpose). Why are these processes important? The ridding of this material can be otherwise correlated with the ‘removal of bodily trash’ and can have positive implications on reduced incidences of diseases such as Cancer and Alzheimer’s disease.

Glucagon (the hormone that works antagonistically to insulin) is directly involved with the metabolic processes relating to autophagy. Once food is introduced to the body, whether it’s by carbohydrate or protein, autophagy is hindered because the metabolic processes of the body become principally focused on the digestive elements in order to achieve homeostasis in that regard. An enzyme called mTOR (mamillian target of rapamycin) is a regulator of autophagy and is directly linked to glucagon function (Glick, Barth and Macleod, 2010). The processes of autophagy and apoptosis are highly complicated (and practically require their own article - but don’t worry, I’ll do that one day!)

Obese persons will benefit from fasting way more than lean persons

Bear in mind, your body doesn’t tap into the essential fat levels which it needs to survive so it will target old proteins and use them for energy. In the case of obese persons - they will burn 90% of their energy in this state from fat - because they have more. As a nutritionist though, I would not recommend this is done immediately (although you could try it). I would recommend you trigger your body into becoming fat adapted first by following a low carbohydrate diet for 4 weeks prior to attempting this. However, persons do try fasting immediately and have good results, and usually the feeling of hunger only lasts for the first day or so.

Does coffee break a fast?

I came across an article written by Sisson (2018) whereby the effect of coffee consumption on numerous aspects of fasting was investigated. Particularly, the two key elements we want to see flourish. These are:

  1. Ketosis - coffee was found to actually complement the outcome of ketosis during a fasting window (Vandenberge et al. 2017; as cited by Sisson 2018). Since plain black coffee has zero calories, this makes logical sense. Thus the fat oxidation capacities theoretically remain unchanged.

  2. Autophagy - coffee was found to induce autophagy in a study carried out on mice (Pietrocola et al. 2014; as cited by Sisson, 2018) so strictly speaking, coffee can theoretically be consumed during a fast to this effect.

I suppose it is more a theoretical concept rather than a factual one, and way more research is needed. However, the implications are plausible.

Types of Fasting

The information below is given using the following references: Fung (2016), and Stewart & Fleming (1973).

There are various fasting protocols which one may use in order to achieve a variety of outcomes. In order to create some form of structure, these are listed below:

  • 8 hours fasting vs 16 hours feeding: in 8 hours insulin is no longer being produced.

  • 13 hours fasting vs 11 hours feeding: this protocol is an easily achievable fasting protocol. The activity of the digestive system has been reduced and levels of human growth hormone (HGH) are increased. There is also increased glucagon activity to cater for falls in blood sugar.

  • 16 hours fasting vs 8 hours feeding: this protocol is the next milestone and is known to promote greater rates of fat oxidation. Fat burning has been dramatically increased at this stage due to an increase of noradrenaline activity. HGH levels are further increased.

  • 20 hours fasting vs 4 hours feeding: this protocol is for adept practitioners of fasting in that they have to consume their macros in just a 4 hour window. Here we have maximal HGH activity.

  • Fasting for over 24 hours: Autophagy is initiated. All glycogen stores are now drained and ketones are released in the circulatory system. The liver is now using gluconeogenesis from internal protein to synthesize new glucose. This is not something to fear. The internal proteins being broken down are old, malfunctioning proteins, especially those found in skin and connective tissue. Your body is literally taking out the trash.

  • Fasting for over 33 - 72 hours: Now you have ketosis. Fat is being broken down (lipolysis) for energy. The rate of autophagy has been doubled or tripled (depending on the current health status of the individual involved. Conversely, the body’s level of inflammation has now been drastically decreased. Triglycerides (stored fat) are broken down into fatty acids and glycerol with glycerol being used in gluconeogenesis (as described earlier).

  • Fasting for over 72 hours: HGH, Noradrenaline and Autophagy are functioning at maximum capacity. This is known as the protein conservation phase because HGH is being used to conserve the most important biochemical and structural components (mostly proteins) in the body. Therefore, energy maintenance is now almost completely derived from free fatty acids and ketones. The noradrenaline is now functioning to prevent the decrease of BMR (described earlier).

There have been records of other, even longer fasts. Think 72 hours is long? Stewart and Fleming (1973) recorded a fast of 382 days. This was carried out by a 27 year old male subject who fasted under supervision for the afore mentioned 382 days. He successfully reduced weight from 207 kg to 82 kg and sustained it till the researchers ceased their follow ups (5 years post termination of fast), at which point the subject retained a weight of 89 kg. During the fast, the subject was only undergoing hydration and was consuming electrolyte supplements, which, theoretically should be carried out by anyone attempting a fast, in order to maintain adequate internal electrolyte status. The remarkable aspect of this study was that the subject did not display any excess skin or stretch marks; presumably because the autophagy processes were ‘eating away’ at the excess skin cells as part of the ‘removal of the junk’ process highlighted earlier.

My attempt on fasting

My general way of living - I try to perform a 16:8 fast as often as possible. As a matter of fact, I have been doing it 6 out of 7 days of the week for the past month. Next week I will attempt to undergo a long fast of anywhere between 5 - 7 days in an attempt to ‘reset the body’ and restore my BMR after a series of caloric restrictions and re-feeds. Stay tuned for my next article; some of you may find it quite interesting.


Catenacci, V., Pan, Z., Ostendorf, D., Brannon, S., Gozansky, W., Mattson, M., Martin, B., Maclean, P, Melanson, E. & Troy Donahoo, W. (2016). A randomized pilot study comparing zero-calorie alternate-day fasting to daily caloric restriction in adults with obesity. Obesity (Silver Spring). 2016 Sep;24(9): 1874-83. doi: 10.1002/oby.21581

Fung, J. (2016). How fasting affects your physiology and hormones. Retrieved from: https://www.dietdoctor.com/fasting-affects-physiology-hormones?fbclid=IwAR3bKiZU9r6yp427-Ad6I-VYVxNXQk-iiAdLkT2ZtV1BweDSvlndU_u41dA

Glick, D., Barth, S. & Kay, M. (2010). Autophagy: cellular and molecular mechanisms. Journal of Pathology. 2010 May; 221(1): 3-12. doi:10.1002/path.2697

Sisson, M. (2018). Does coffee break an intermittent fast? Retrieved from www.marksdailyapple.com

Stewart, W. & Fleming, L. (1973). Features of a successful therapeutic fast of 382 days’ duration. Postgrad Med J. 1973 Mar; (569):203-209.