Enhance memory and brain power with intermittent fasting – part 2


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Fasting for improved performance

Going with out food seems like a counter intuitive way to improve health. The mention of fasting conjures up images of anorexic models going to extremes for their profession. But done right, fasting leads to benefits. In the previous blog in this series we saw how intermittent fasting (IF) or caloric restriction (CR) demonstrated the following:

  • Memory improvement
  • Improved cognitive function
  • Improved resilience to stress

The benefits don’t end here either. In this blog I talk about different fasting protocols and my experience on a five day fast.

Fasting protocols

There are an infinite number of ways to carry out a fast. There’s the 5:2 diet – fast or restrict calories for 2 days and then eat what ever you want on the 5 days. There’s the alternate day fasting – eat nothing for one day and then eat whatever you want for the next. You can restrict calories to a very low amount for several days. Here are the protocols I’ve used:

  • Pure fast for 16-24 hours: Nothing but black coffee and water for a window of 16-24 hours and this time can include time sleeping. If I was doing a 20 hour fast for example, I would finish dinner at 8pm and  wouldn’t eat until 4pm the next day.
  • Pure fast for 5 days: Nothing but black coffee or pure teas for 5 whole 24 hour periods. This is challenging to do (see my diary entries below), particularly the first couple of days dealing with hunger. This is something I do 1-2 times a year to reset hormones and to do a complete detox.

Some people, rather than go full out on a pure fast will restrict calories – e.g. for 5 days they will eat a daily maximum of 200-300 calories. Eating a small amount creates larger hunger pangs and opens up the temptation to snack a bit more and go over your target calories. If doing a pure fast is too daunting or difficult, there are options for dealing with hunger:

  • Bulletproof® intermittent fast: a 16-18 hour fast where you’re allowed to drink Bulletproof® Coffee (no added protein) for the fasting window. The fats in the coffee keep you satiated whilst the XCT™ or Brain Octane™ oil stimulates ketosis (see here for more details).
  • Using combinations of branch chain amino acids (BCAA) and an MCT oil such as Brain Octane™. Again the MCT oil stimulates ketosis and the BCAA acids get burned up instead of muscle protein. Muscle wastage can be a problem if you don’t go into ketosis easily.
  • Bulletproof® protein fast: restrict proteins to less than 15 grams in a 24 hour period. You can still eat carbs and fats, as long as they’re on the Bulletproof end of the scale.

Five day fast – a personal experiment

Here are my journal entries from doing my most recent 5 day fast, which I kicked off for the period of just after Christmas up until New Years Eve. This was a great way of resetting the system after the Christmas excesses. For this period, I worked from home which meant it was easier to avoid the temptations to eat.

Journal entries

  • 19 hours in (10am): Doing fine. no real hunger pangs, have been awake for about 2.5 hours. Have had 2 black coffees. First day back working so finding it trickier to get back into work mode.
  • 29 hours in (8pm): Hungry, but not desperately. Have spent the whole day working and still have reasonable energy levels and focus.
  • 40 hours in (7am): A background sensation of hunger exists. Feeling a little weak and fluey. I have a cold/flu but think this is unrelated to fasting (I had a cold before starting the fast).
  • 52 hours in (7pm): Really starting to feel hungry. stomach is contracting big time.
  • 76 hours in (7pm): Hunger has subsided. Skin has been a bit flakey (this I reckon is due to lack of carbs). Have been pretty much working long days. Feel like I can still keep going. Energy and focus levels are high.
  • 116 hours in (11am): 4 hours to go. Had the most awesome meditation last night. Lack of focus or energy has not been a problem in terms of work that requires thinking, although I don’t feel physically strong enough to do any intense physical exercise (and wouldn’t recommend that!!). I’ve got red blotches on my face- as if I’ve had a night on the red wine. This has happened before – on protein fasts, exercising and sometimes when I’ve overdone the fat. It could be due to drinking too much caffeine (I tend to overdo caffeine when I don’t eat) or could be from being in a state of deep ketosis.

I ended the fast a little bit after 120 hours with a large meal. I felt like I could’ve kept going.

Heart rate variability

I seen big improvements in my Heart Rate Variability (HRV1, to keep things simple, this is a measure of stress). My HeartMath HRV score increased to 6.5 average per HRV training session, from a previous of 6.0. This was a big step change – previous maximums had only increased by 0.1. This increase was 5 times that. This is noteworthy as the cardiovascular benefits have also been noted in the literature2.


Ketone levels are an indication of how much fat is being burned. Ketone levels remained at 0.05 mmol/L (light ketosis) for the first 48 hours. They increased to 0.4 mmol/L (moderate ketosis) after the 48 hour point up until I tested with 4 of the 120 hours remaining when they registered 8 mmol/L (deep ketosis). Moving into deeper into ketosis takes the hunger away.

Fasting –  a free and powerful hack

IF kicks off mechanisms in the body which enhance energy levels, alertness and intelligence – all useful from an evolutionary stand point if you’re close to starving and need to move and figure out where to get your next meal. Still, in modern times it’s a super cool hack to get you feeling great and into the flow state.

Thank you for reading. In the mean time… keep hustling


Have you tried intermittent fasting? Please leave me a comment below.

If you are interested in trying out a FREE 7-day meal plan you can grab a copy of that here. Just add your details and we’ll get that over to you. 

Bulletproof and Brain Octane are registered trademarks owned by Bulletproof Digital, Inc. Bulletproof Diet, XCT and Upgraded are marks owned by Bulletproof Digital, Inc.


  1. https://en.wikipedia.org/wiki/Heart_rate_variability ‘Heart Rate Variability’
  2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2995774/ ‘The impact of religious fasting on human health’

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