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Well, this is a huge topic to jump into, but with so much talk about fasting out there at the moment, it’s likely a good time to discuss. Right! Let’s talk fasting.

What do we mean by fasting? What type of fast is best?

  • Broth fast?
  • Juice fast?
  • Intermittent fast?
  • Water fast?
  • Religious fast?
  • 24 hour fast?
  • Alternate day fast?
  • 5:2 fast?
  • Extended fast?

Whoa – not so fast!

Historical perspective on fasting

Picture this: as hunter-gatherers, we would rise in the morning and hunt all day. It is likely we had a nice fatty meal the night before, with maybe some liver, brains and a whole lot of animal fat (if the previous day's hunt was successful). There’s every chance we were in ketosis and now needed to go out there on an empty stomach and hunt down another meal. Of course, this isn’t exactly how it went, not all of the time, but it highlights the point. From an evolutionary perspective, and before the agricultural revolution, we had periods of scarcity when we didn’t have a meal ready to go. By definition, this is fasting - an absence of eating – and we fasted all the time throughout our evolution.

References to fasting have popped up throughout history. Religious fasting is perhaps the most famous and ancient form of fasting. A physical and religious fast is aligned with a cleansing, a purification – in essence, a detox – and this supports a spiritual cleansing. All major religions fast.

Fasting has popped up since the agricultural revolution too. Benjamin Franklin said, ‘The best of all medicines is resting and fasting’.  

In ‘The Complete Guide To Fasting’ by Jason Fung and Jimmy Moore, they cite Mark Twain as having said, ‘A little starvation can really do more for the average sick man than can the best medicines and the best doctors’. Of course, that’s amusing, but Mark Twain wasn’t a healthcare specialist – so where’s the science that says fasting will benefit us?

How did our forebears get the energy to continue on an empty stomach with no calories to fuel their day? It is the belief that fasting is a natural state for which we have developed adaptations.

You’re Already Fasting Every Day

Anyone who has eaten breakfast has broken their fast. Hence the term, ‘break’ fast. We are designed to have periods of not eating, and can safely extend this period out from 12 hours, for example 6:00 pm – 6:00 am without food, to 15hours (6:00 pm to 9:00 am) without food. A 15 hour fast each night is a form of intermittent fasting. During those 15 hours, we have the opportunity to engage all the clean-up processes in our gut, rest, heal and repair. Proponents of intermittent fasting such as Joseph Mercola, regularly undergo a 20 hour daily fast for periods of time, eating only from 2:00 pm to 6:00 pm on each day. This was popularised as the Warrior diet by Ori Hofmekler, who aligned his eating with our ancestral eating patterns. I’m not suggesting this is for you, It’s merely an example of how we can utilise fasting while still having only small disruptions to our lifestyle.

Common Concerns Of Fasting

The irony is that the more society has ensured a steady food supply, the more fear we have of going without. The food industry has made regular snacking a thing when it shouldn’t be ‘a thing’. Imagine if you worked any other part of your body as much as you worked your gut? Here are some common concerns, that are more aligned with starvation than a therapeutic fast:

  • Electrolyte imbalances
  • Blood sugar drops
  • Blood pressure drops
  • Muscle wasting

These are all proven untrue in the research around fasting. The body has a wonderful ability to maintain its internal environment. Firstly, we should always keep up ample fluid intake no matter what we are doing, as this will help maintain your blood pressure. When the body has a sudden decrease in electrolytes, sugar, or even fat, it intuitively, in all its miraculous cleverness, conserves what it needs to keep us functioning.  In fact, the body says, “I’d better clean up here and get myself functioning optimally so I can survive through this.” We will see how this works below.

Fasting To Fit With Your Lifestyle

Given that periods of time without food were traditionally sporadic and unpredictable, it can work in our favour if we mimic that same situation. For example, if you are at a party full of carbohydrate-rich foods or on a plane flight (whoever had access to real food on a plane?), these may be times to give your body the opportunity to fast. We avoid food that will make us sick or feed our pathogens, and we give our gut a rest at the same time.

Main Indications For Fasting / Benefits To Fasting

The primary benefits of fasting are detoxification and immune system regeneration. Here is a summary:

  • Fasting has been shown to increase mitogenesis – that simply means we grow and renew our mitochondria when in a fasting state.
  • Decrease insulin levels and aid weight loss for those who require weight loss for health. If you are insulin resistant, fasting can be a great way to reverse insulin resistance and regain blood sugar control.
  • When the gut is rested entirely, it has an opportunity to heal and repair where needed.
  • You function in ketosis, which is associated with lower oxidative stress and free radical production (this means less inflammation). Ketosis has been shown to protect us from degenerative brain diseases and cancer.
  • Appetite control. Fasting is easier when you are already used to fat adaptation and ketosis,however, it can be really unpleasant if you have a high carbohydrate diet.
  • Immune system regeneration.  Fasting triggers stem cell activity and the creation of new white blood cells – key players in your immune system.
  • Slows ageing.  Research demonstrates that caloric restriction plays a role in decreasing ageing but is very impractical. Intermittent fasting has been shown to have similar benefits in relation to ageing.
  • Increased metabolic rate.  Whereas regular caloric restriction has been seen to drop metabolic rate (seen Biggest Loser, anyone?) fasting increases metabolic rate, allowing you to continue to function with appropriate energy levels.

Starvation Versus Adaptive Fasting

In a nutshell, starvation is not voluntary and involves a restriction of calories in circumstances where you do actually require them. Fasting, if continued for too long, can become starvation and lead to the breakdown of muscles, organs and other tissues. Proper fasting with adequate hydration will preserve lean muscle, allowing you to get out there and hunt that gazelle. We would not have had a survival advantage if we lost our metabolic rate, compromised our immune system, burned muscle and ran out of calories. This is the difference between optimal functioning with periods of fasting versus prolonged involuntary lack of food.

Fasting vs Ketosis – What’s The Difference?

There certainly are similarities between ketosis and fasting. Do you remember the information in the very beginning of module one where we discussed the process of autophagy? When we are in a fat-as-fuel state of ketosis, our body undergoes a cleanup where the ‘Pac-Man’ style cells called ‘macrophages’ or ‘autophages’ get around and gobble up any defective cells or debris. They recycle where able and clean up bacteria and viruses hanging around causing trouble. Further to this, many bacteria and yeasts only have a pathway for fuelling off sugar – hence the ketogenic diet starves out the pathogens we don’t want and our ‘phages’ sweep the floor.

All of this happens in fasting, too.  What’s the difference?

When we fast: when our stomachs are empty we employ a mechanism called the 'migrating motor complex' or MMC. This is like a wave that moves through the stomach and small bowel cleaning up debris and bacteria. It is known as the house cleaning wave. During fasting, when the stomach is empty, the MMC activates every 90 – 120 minutes. We suspect this plays a role in interrupting the formation of biofilm. You do not need an extended fast for this. It will happen during your overnight fast. Eating close to bedtime has been shown to interrupt the MMC activity. So we still aim for a good break between dinner and breakfast.

A period of fasting will achieve much lower insulin levels, higher growth hormone, higher adrenaline and cortisol. Basically fasting is an intense ketogenic state, and many of the fasting benefits can be gained through a ketogenic diet without some of the contraindications that you will see below.

When Not To Fast

  • Underweight
  • Still growing (children and teens)
  • Adrenal issues
  • Thyroid issues
  • Pregnant or breastfeeding
  • Malnourished
  • Trying to conceive
  • Conditions such as Type 1 diabetes
  • Taking medications that require food

When fasting, you are mimicking a time of scarcity.  This is not a situation where your body would be happy to release an egg (ovulate) or grow a baby.  The same situation exists with significant hormonal imbalances. Fasting also calls upon increased secretion of cortisol and human growth hormone, so if your body is not in a place where you are able to respond appropriately to a fast then it is best to seek a consultation with a practitioner and address these issues first.

Types Of Fasting

The most common type of fasting that you already do to some extent is the Intermittent Fast - a little period of time each day without food.  For most of us this is overnight. We can safely extend this into the morning without risk. Longer fasting, such as 3-5 days, can have profound benefits for the immune system and health of our mitochondria and our brain function.

Other types of fasting such as alternate day and the 5:2 diet, made famous by Michael Mosley, involves taking in a very low calorie diet 2 out of 5 days or alternate days. This may be a better option for people who want to fast but take medications and cannot go without food entirely.

Longer, extended fasting beyond 5 days is best medically supervised and is often undertaken to meet a specific health goal such as diabetes, obesity and insulin resistance.

Juice fasts, in my opinion, are not fasts at all and usually contain too much sugar that block potential benefits of fasting. 24 hour fasts are popular as you can eat dinner one night and fast until dinner the next night. This is psychologically easier to achieve than extended fasts and can bring many hormonal benefits such as insulin balance, enhanced ketosis, mental clarity, gut cleaning and autophagy.



Fasting is not for everyone all of the time. If you have hormonal imbalances and gut healing to undertake, fasting may be better taking a back seat until you have these under control. Fasting is an amazing tool for maintaining peak health, cancer prevention, brain function, immune system health and hormonal health – BUT, at the right time for you.




  • Mercola, J. (2017) Fat For Fuel: A revolutionary diet to combat cancer, boost brain power, and increase your energy. Hay House; California USA
  • Winters, N. and Kelley, J. H. (2017) The Metabolic Approach to Cancer: Integrating deep nutrition, the ketogenic diet, and nontoxic bio-individualised therapies. Chelsea Green Publishing: Vermont USA.
  • Fung, J. and Moore, J. (2016) The Complete Guide To Fasting: Heal your body through intermittent, alternate day, and extended fasting. Victory Belt Publishing; Canada.

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