My experiment with fasting

Over the past few months I have been playing around with fasting. Fasting is something that has been done for thousands of years and is a part of many religions. It's interesting that a lot of food practices passed down via religion and culture tended to be favourable for our health. Foods with religious symbolism such as pigs or shellfish were prone to parasites and causing infections in those that ate them. Naturally people started to avoid them as a survival mechanism. So we could deduce that people in ancient times found some benefit from fasting, but we can't really be sure. It's interesting that studies have shown that Muslims observing Ramadan have had positive health benefits associated with their fasts.

What we can be sure of is that humans did not develop with an abundance of food available to us around the clock, every day. We certainly didn't develop eating 3 meals a day either. These are fairly recent developments in the history of humankind. Throughout the Paleolithic era we were hunter gatherers and would eat whatever we could get our hands on. There would have been no surety of when the next meal was coming and there would have likely been spells without food. So why does this matter? The way our bodies process and digest food, from our stomach and intestines to our liver, pancreas and gall bladder has been driven by our history. The Paleolithic era was a considerable part of humankind's history and thus would have had a big impact on our biology. The problem is the mismatch between our current lifestyle today and what our bodies have slowly developed for. This is the underlying principle behind the Paleolithic/Paleo diet or Paleo lifestyle which has been somewhat bastardised.

I like to use a Paleo template for my lifestyle, as I believe, if this is what drove our biology then this should be a good starting point to lead a healthy life. I don't think fasting is widely considered a part of the Paleo diet, but I believe it should be.

On researching and writing this article I realised the formation of the word Breakfast - Break Fast. It really just refers to the first meal of the day. This does not have to be first thing in the morning. When I was a teenager getting up for school I wouldn't really feel hungry, but would force down breakfast as the conventional wisdom was that it was good for you. It used to make me feel sick sometimes as I felt my body wasn't ready for food yet. I wish I had listened to my body back then, which I think is an underrated thing to do.

Types of Intermittent Fasting

There are many different types and variations but this is a brief summary.

1) Whole day fasting - The 5:2 diet has become very popular over the past few years whereby people restrict calories on two days of the week. Sometimes 500-600 calories, however these we have to be consumed in a short space of time. Other people will go 24 or 36 hours without food.

2) Time Restricted Feeding usually involves daily fasting eating all your meals within a 6-8 hour window (e.g. between 12pm and 6pm or 12pm and 8pm). This gives your digestive tract a 16-18 hour break from doing anything. Sometimes this is referred to as 6/18 or 18/6 fasting or 8/16, 16/8 fasting depending on the time interval you are choosing.

Benefits of fasting

The research on fasting is somewhat limited at the moment. A lot of animal studies have reported great benefits, but these need to be repeated in human trials. The benefits below are from Precision Nutrition's guide to fasting which is a great read if you have time ( Funnily enough it was posted a few days after I started writing this blog post, but has been a great help.


  • blood lipids (including decreased triglycerides and LDL cholesterol)

  • blood pressure (perhaps through changes in sympathetic/parasympathetic activity)

  • markers of inflammation (including CRP<, IL-6, TNF, BDNF, and more)

  • oxidative stress (using markers of protein, lipid, and DNA damage)

  • risk of cancer (through a host of proposed mechanisms


  • cellular turnover and repair (called autophagocytosis)

  • fat burning (increase in fatty acid oxidation later in the fast)

  • growth hormone release later in the fast (hormonally mediated)

  • metabolic rate later in the fast (stimulated by epinephrine and norepinephrine release)


  • appetite control (perhaps through changes in PPY and ghrelin)

  • blood sugar control (by lowering blood glucose and increasing insulin sensitivity)

  • cardiovascular function (by offering protection against ischemic injury to the heart)

  • effectiveness of chemotherapy (by allowing for higher doses more frequently)

  • neurogenesis and neuronal plasticity (by offering protection against neurotoxins)

Eating a good diet will give you most of these benefits anyway. Intermittent fasting is potentially another way of doing it and may add to the effect. We don't currently know if it is better, equal to or worse than eating a healthy diet at regular intervals. I don't see it as one or the other. We should be very adaptable and I think that mixing up our eating intervals and energy sources is not a bad thing.

For type 2 diabetics I think it can be a great tool to help control those blood sugar levels.

If you are following a ketogenic diet, then it is a fast and great way to get into ketosis. This is where your body uses fat rather than glucose as an energy source.

My Experiment

I have been doing time restricted feeding randomly over the past year just skipping breakfast on occasions and then only eating lunch and dinner, normally within a 6 hour window as this suits my lifestyle. My recent experiment over the past 2 or 3 months has been eating my last meal on Sunday at around 6pm and then not eating again until 7:30pm on Monday (25 hour fast). I found this easier than I thought. Lunchtime is the hardest in terms of feeling hungry, especially when people try to tempt you, and then as the day goes on it gets easier. Keeping busy is key. I always go for a walk at lunchtime and I am busy at work the rest of the day. I know I would struggle to do it on a day when I wasn't working or very busy at home.

So what benefits and negatives have I found from fasting?

Without any blood tests or glucose monitoring, all of my results are purely subjective. I never weigh myself either, so have no idea what happened to my weight or body composition over this time period. I don't feel my training was consistent enough to make an informed judgement.

I definitely felt more alert and focused when I fasted.

I found I ate a little more on a Monday night after the 25 hours fasting, but didn't feel ravenous and pig out.

I feel it gave me a better feeling for true physiological (body) hunger rather than psychological (mind) hunger.

Last week on my fast day I went bouldering during lunch rather than walking and didn't feel my performance suffered or have any lethargy afterwards.

It made me appreciate food more.

I saved time by not having to prepare 2 meals on that day. My lunchtime was also longer so I could be more active with the time I would usually be eating.

I didn't find any major negatives other than the tough willpower it took to resist people offering me things.

Will I continue to fast?

The answer to that is most definitely yes. From the limited research available that I have read there seems to be different benefits for different lengths of fasting, so I intend on mixing it up between a whole day fast and 18/6 or 16/8 fasting. Initially it might be easier for you to follow a set regime and then when you get more confident you can start experimenting. We are also unique and what works for one person, will not necessarily work for you. This is especially true between men and women. Fasting has been better studied on men than women. It has been postulated that as women did more of the gathering they may have had a more stable food supply. So you may find a short fast is better for you. Something Precision Nutrition posted in their article was that he would often fast when he was travelling as this was a time when good food choices were often unavailable. I thought this was a great idea and something I will try.

Who is fasting not for?

If your diet is not great anyway then fasting will not be a magic answer. It has be shown that be who skip breakfast tend to then binge later in the day to make up for it. This tends to happen if you eat a lot of hyper palatable processed, refined foods as these are much easier to binge on.

It has not been very well studied on children or the elderly.

During pregnancy women need a greater calorie intake so shouldn't be restricting it.

Athletes or people doing a lot of training may struggle to fit in enough calories to fuel their pursuit. It's still possible to get good results as long as you are getting enough calories.

If you are unsure if fasting is for you then consult a medical professional to discuss your individual needs.


On every blog post on health I could ever right it goes without saying that you have to have the basics right of a healthy diet, regular movement/exercise, manageable stress and good sleep. Most people haven't mastered those yet and should work to do so. Fasting is not the magic answer for fantastic health and wellbeing. However I do feel intermittent fasting could help support those goals and is likely to be closer to what our ancestral eating pattern looked like. The postulated benefits are very promising and I feel it can give you a better relationship with food, if used correctly. With few reported downsides why not give it a try and let me know how you get on.

If you want some further reading then these are two great websites with a wealth of resources that have helped me research this article. - search the website for intermittent fasting

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