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Here’s the deal: I’ve fasted before.  I’ve water fasted.  I’ve fat fasted.  I’ve juice fasted.  I once subsisted entirely on cold pressed vegetable juice and coconut water for 14 days.... and wanted to go longer.  I’ve done Ramadan (more than once).  I’ve tried intermittent fasting (daily and weekly) and Bulletproof intermittent fasting, both for extended periods of time.  I’ve also done a whole bunch of self- and Instagram-inspired health and fitness 30-day challenges, including Dry July and Sober September (I think I coined that last one)... all because I think fundamentally that the best way to get an opinion on if something works for you or not is to try it out yourself. 

So yes, I’ve fasted before.  And these are some of the things I learnt:


1. Your brain functions differently when it you are fuelling yourself with fat versus when you are fuelling it with sugar.

There are a lot of terms flying around in the nutrition community these days with the increasing prevalence of fat-based diets becoming mainstream.  Words, phrases and acronyms such as “fat adapted”, “sugar burner”, “ketones” and “ATP production” which can easily lose people who don’t have a passion for foundational science (or a basic background in biochemistry).  There are lots of articles and theories out there describing the scientific processes that your body goes through when your cells utilise fat vs sugar... but when it comes down to it, the reason we all want to be healthy is because we all want to feel good.  Building from this, all the experiential data regarding how fuelling your body/brain on fat vs sugar boils down to this:


  • When your brain is fuelled on fat (ketones), you feel switched on, have more energy, and can focus better for longer periods of time.
  • When your brain is fuelled on sugar (glucose) you feel tired, lose focus and concentration easily, and experience “brain fog”.


Which is all true and logical.... but it's missing something.  For me, the cognitive energy I experience when eating a high-fat diet is markedly different from that when my diet is based on sugar or even glucose (i.e. when juice fasting), and the first I actually felt it happening, I realised it was more than just  “energy” or “concentration”.  

I describe it in terms of music; the difference between an opera solo (ketogenic brain) and a Lo-Fi drum and bass remix (glucose brain).  There is a fluidity and narrowed strength when you focus on an idea when your brain is fuelled by ketones that is very difficult to achieve when your brain is fuelled by glucose - because sugar is metabolised differently in the body.  It is designed to give you a quick, short burst of energy - and it does that for your brain, too.  Quick, sharp, short flurried bursts of concentration, many sparks of different ideas - but no ability to sustain that energy without supplementation for long periods of time.  When your brain is fuelled by fat, there is a precision and power it exhibits which you can learn to skilfully channel with experience.  Just as one learns to channel the voice in opera, or language for poetry, or (an) instrument for music, or colour and shape theory for fashion and design - you can train your mind and consciousness similarly.  The best example of this?  Learning meditation and teaching your mind to affect your body (e.g. slowing down your heart rate and training your body into a state of coherence) to help you deal with stressful situations.


2. True hunger expresses itself as fatigue and weakness, not a desire to eat.

Please note - this is not an observed distinction between hunger and a craving (although that is an important and valid distinction to learn to make).  I had the privilege recently of hearing Nora Gedgaudas (author of Primal Body, Primal Mind) speak on “The Paleo Way” tour in Australia, and she asked the audience two questions, the responses to which were meant to elicit whether or not you were experiencing blood sugar issues/imbalances:


  • How do you feel when you haven’t eaten for 3-4 hours?  Do you have brain fog, fatigue, cravings for certain foods?
  • How do you feel immediately after eating?  Do you feel more energised, or more tired?

After letting the audience think and reflect, she continued:


“If you answered yes to any of those things, then you have blood sugar issues.  Because how should you feel when you haven’t eaten for 3-4 hours?  Hungry.  And how should you feel immediately after you’ve eaten?  Not hungry.”


When I juice fasted, my hunger would manifest itself as muscle fatigue.  I was not “hungry” in the traditional sense of craving food/wanting to eat; my body just felt tired, and my brain could not focus.  Attempting to exercise during the days I had slacked off on calorie consumption also proved incredibly difficult - I was weak, and I learnt very quickly to distinguish between physical weakness and weakness of will... because yes, you can compensate for physical weakness with mental strength to some extent, but it cannot take you the entire way.

You need to have both, working together in synergy, before they can help you achieve your goals.


3. Coming out of a fast in a controlled manner is the hardest part.

Controlling any change is difficult, because when there is chaos there is opportunity - and this can be a positive aspect or a very dangerous one, depending on which side of the fence you currently stand.  It can be a fantastic gateway to thrust new ideas and habits on yourself for the better, but it can also leave you very vulnerable.

We’ve all heard those stories of people completing juice fasts, or getting to sundown at Ramadan, or finishing Lent (or an alcohol-free month) with a huge binge, to “compensate”... which completely defeats the true point of fasting.  You fast to set yourself up for the future - it is a stepping stone.  Please, still celebrate the completion of a fast; it is an achievement that should be acknowledged and appreciated every time - but realise that it is always the beginning of the future.  As in Bikram Yoga, when you get halfway through - you take some time to acknowledge your standing series, take some water if you wish, turn around and lie down in Savasana to prepare you for the spine strengthening series.  But remember, Savasana is still a posture, with a fixed form, and for most it is the hardest one to master.

The trick to managing this change effectively is to plan ahead... buy your food in advance and prepare your meals.  And remember that it’s just the end of the beginning, and there is so much more in store for you.


4. Restriction brings clarity and strength.

When I fast - 24-hour fasts, 36-hour fasts, Ramadan, etc - suddenly life comes into focus; I can ground myself.  There is so much to see and experience in the world that it is usually so easy to get caught up in it all - in new foods, new experiences, shiny cars, shoes, holidays...  It is exciting, but it can also be addictive, and as with any addiction, the first step to analysis or recovery is acknowledgement.  I propose the following is also true:


  1. You can only acknowledge you are addicted to something once you believe you are actually addicted to something.
  2. That conclusion comes from analysis and evaluation of your current situation.
  3. You can only analyse/evaluate something from an objective standpoint if you first remove yourself from the situation ("take a step back").


This is the primary reason for all religious fasts - it is a set period of time for teaching self-reflection.  In nutritional fasting (cutting out alcohol, or dairy, or sugar, or grains), it is also an invitation to really examine yourself and figure out - for yourself - if what you are putting into your body is benefitting you, or if it is hurting you.


My experience juice fasting gave me great physical energy and, yes, I lost some weight in the short term and was not hungry or tired as long as I kept my calorie intake sufficient.  Fasting was also easy... not having to think about food meant I had so much extra time to focus on other pursuits - work, hobbies, yoga.

I posit, perhaps that this may account for the positive experiences of people on a High Carb, Low Fat Raw Food Vegan Diet - because a lot of the claims are actually truthful.  You do lose weight.  You do have a lot of energy.  And yes, the food tastes great.  But when it came down to it, I could not retain the same mental focus on a glucose-based diet as when I was on a ketogenic diet, and that was a huge issue for me.

Having said that, I also believe that a long-term strict ketogenic diet does not work for me.  There is a theory that long term ketogenic diet may actually have negative health consequences for women because of the effect of lowered leptin levels on oestrogen and progesterone - and this is something women should take care to watch out for, especially if they are very active.


The solution for me?  Instead of 65-75% of calories coming from fat, I dropped that down to 50%, and kept protein intake moderate, at approximately 15-20% of total calories (around 50g protein, coming from fish/seafood* and occasionally eggs) and increased my consumption of carbohydrate (glucose) to around 80-100g/day.

Voila! An actual balanced diet. 

*I am Pescatarian

Guest Author
Guest Author

This article was contributed by a guest author with expert knowledge in their field.

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