Benefits of fasting: My 72 hour experiment


Why is fasting good with keto?

Longer fasts outside the regular intermittent fasting are a really good way to up your keto game or to challenge yourself as well as having some really good benefits.

As you progress beyond 16 hours of fasting, if you measure your blood ketone levels you’ll notice that these start to slowly rise above your regular baseline ketone level. Your ketones will also increase each progressive morning of an extended fast. Increased ketone levels are a signal that your body is burning fat for fuel and using fatty acids (which through oxidation) to produce ketones inside your liver. 


Will you be hungry?

“Ghrelin is a peptide secreted in the gut that is reduced on feeding and has been implicated in the regulation of feeding behaviour and energy balance. Obese subjects have lower fasting ghrelin concentrations than do lean subjects but have impaired suppression of plasma ghrelin in response to a meal.” – Heilbronn et al., 2005

So while you may be a little hungry while fasting, you can take comfort that it’ll get easier with time and practice, at least during a multi-day fast. Also, it's a really good idea to make sure that you have something fun or productive to do when ghrelin peaks to make sure you stay away from those tempting foods

Fasting tip: Keep a busy schedule, particularly on the first few days of a prolonged fast, and keep plenty of flavorful drinks (flavored water, tea, coffee, etc.) around when food cravings strike. So for me, while working in a keto bakery, to stay super busy baking was especially important so I didn't even think of eating.


Fasting while working in a keto bakery? Am I crazy?

Now I run a UK keto bakery. And you can imagine trying to bake these lovely cakes and other bakes which are, you know, perfect for the keto and low carb diet (wholesome plug here, click here) would be a perfect place to work. However, when you're fasting, not so much. I think because I'm used to the smell of the cakes and I do the baking as well as working with them every single day meant they didn't really tempt me, and it's almost like there's a switch in my head telling me that I shouldn't really eat so I didn't! My wife Basma even had a ribeye steak last night (day 2 into the fast), and I didn't even feel remotely tempted to eat it. 


The importance of fluids: 

Now fluids, of course, are really important when fasting and like I said I had too much black coffee in the first day so the second day and the third day I've now been having herbal tea. I think it's a better way to get my fluids in. And also sipping on the old saltwater as well (lo salt has potassium and sodium in so is a really good salt to dissolve into water). Although one thing that's interesting, I'm going to the toilet a lot more often. So I think that's the sign that my body has adapted and that fluid is going through quite quickly.

It’s important to stay hydrated on a prolonged fast. For one, drinking water and unsweetened teas keep you feeling more satiated while you are in your fast. 

You can address your electrolyte needs while fasting by drinking teas with some pink salt added and taking potassium and magnesium supplements – a daily multivitamin may also work if it contains these electrolytes but if you get symptoms of nausea then cut back on those electrolytes. Also, look for packets of electrolytes designed for hikers and runners for example but watch out for those packed with maltodextrin and bad sweeteners: see our list of sweeteners ranked here! 


Why did I want to do a 72 hour fast?

So the reason I've decided to do a fast is that I wanted to learn more about what I could challenge myself to do further in my journey with keto. And so that's why I wanted to kind of have a go at doing this, but I decided I wanted to get some expert advice first. That's why I spoke to my good friend Eranda who himself has lost lots of weight since last summer, and now does intermittent fasting and fasts on a Monday and a Tuesday, every single week and is now in the routine of doing that. Eranda has also been on my podcast UK Low Carb: check out his episode here

Eranda gave me some great advice about fasting, and he said that one of the best things to do is make sure you get your meals right before you start including making sure that I was getting lots of electrolytes, cutting out all the carbs that I could in my diet before I started my fast started to be best prepared to be fat-adapted to go into the fast.

I also spoke to Cynthia Thurlow and Cynthia is an expert in fasting, she, in fact, made a TED talk a few years ago, talking about the benefits of fasting. When I spoke to, Cynthia with Eranda she advised me about the benefits of fasting and some of the mechanisms that happen. She said that on the first day, the glycogen in the body is used up. By the second day, people feel a bit more ill because they are converting to being fat-adapted and by day three and four, they are then burning fat very efficiently, the fat oxidisation is happening, whereby the body is then burning its own fat stores and releasing ketones. She told me to make sure I kept my electrolyte levels up high so that I didn't feel ill, and that apart from that, I should really enjoy the experience. 


Before the fast:

So, Sunday, the night before the fast. I was at my parent's house and my mom knows I'm currently doing carnivore. So she made me a lovely meal, including some lamb chops and wild venison. I had that with a little bit of butter. And I decided to really enjoy it so I had a great meal I added some sausages as well. And that was my last meal and then in the evening at nine o'clock on Sunday. I had a big cup of tea with double cream in it, knowing that was gonna be my last tea for a few days.

*Just disclaimer here tea for me is a way of life so that was a big deal, but I really did enjoy it.*


DAY 1: 0-24HR

On Monday morning I woke up and I felt absolutely fine. I was very aware that I was fasting. And I thought to myself, well, maybe I'm going to feel hungry, but then I never had breakfast anyway so why would I, and at around two in the afternoon I actually felt quite hungry because that's the normal time I would eat. However, I didn't actually feel too bad at all. So, I thought to myself, well, I'll just sip my saltwater, and the hunger pangs went very quickly. Just on the electrolyte front, I did take a pinch of Himalayan pink salt that morning, and I had some salt in a bottle of water which I was swinging throughout the day, and I was drinking black coffee. I had a whole cafetiere of coffee in the morning and again another cafetiere of coffee in the afternoon. And when I got home is feeling a little bit funny. I thought to myself maybe this is because of the fast but it turns out I just had a bit of a caffeine overdose so I decided after that to be a little bit more careful with my caffeine intake.


DAY 2: 24-48HR 

I had heard day 2 was going to be the most challenging. However, I found I was really lucky in the fact that day two wasn't hard for me at all. I think because I do keto already and have done for a while. I've been following a low carb diet now for a year or more or less on and off. But with keto, recently I've been much more strict than the previous three or four months. In particular, I've been carnivore and OMAD for the last month and so I think this meant I'm probably fat-adapted anyway. So, even though I eat too much protein, I think I'm used my body's used to running on protein and fat only and not carbohydrates. And so for that reason, day two is actually pretty easy.


DAY 3: 48-72HR

Day three however I did wake up with a migraine at 5 am. Now, I'm a migraine sufferer, so it's hard to know if it's been caused by the fast or maybe it's been something that's been brewing because I've changed my sleep pattern slightly and I'm quite sensitive to sleep changes. So I did wake up this morning feeling really ill, to the medication that the doctor has prescribed to me, and I feel okay now, but I'm going to carry on with the fast because I really don't  And if I'm feeling better than fairly fast isn't a factor in causing the migraine. I'm just gonna make sure I keep my salt intake up today, and my fluid intake up as well. If I feel well enough by this evening, that this is on Wednesday (15th July), I'm going to do an extra day tomorrow as well, to see if I can do a four day fast.


What happens beyond 72hrs?

Eranda told me that actually the sweet spot you're trying to aim for is day three and four and beyond and if you can do day 4 maybe 5 that's when you get the most amount of fat-burning happening. By day five you also get the cells started to slide into stem cell creation as well and regeneration. Autophagy also occurs in the fast which helps the cleaning out of dead and 'broken' cells. 

That's my fast so far, feeling much better now in terms of my migraines as they seem to be going away slowly.  I will keep everyone posted as I go through this and update as I continue in my fasting journey.

find more resources here:

Check out my podcast - UK Low Carb episode documenting all of the above




  • Sam

    A brilliant first fasting attempt or should I ssy success, and the Podcasts are really Interesting..

  • Sam

    A brilliant first fasting attempt or should I ssy success, and the Podcasts are really Interesting..

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