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My experience of doing a 5 Day water only fast

As someone who has spent most of my life morbidly obese, Christmas has always been a challenging time. I seem to have been trying to lose weight my whole life, and the festive season, with it’s multitude of social occasions, plentiful food and drink and apparent license to over indulge has always been a bitter sweet time. I could spend the previous 2 months losing 5 or 6kg, and then in the space of a couple of days, pack on another 8kg. 


I decided this year I would try something different. I have tried many different types of eating, from straight out calorie counting, Lite’n’Easy, Keto, Plant Based with mixed success, and certain failure. Mixed success in that I lost alot of weight, but certain failure in that I was 46, and weighed in at 138kg, so nothing stuck or was sustainable. About the only thing I had not tried was not eating at all!


I have been toying with he idea of intermittent fasting for a while, but hadn’t been prepared to give it a go. Then I listened to some podcasts talking about prolonged fasting and its many benefits and I thought why not give it a go.(If you want some good info on this, check out Dr Peter Attia, Rhonda Patrick, Tim Ferriss podcasts).  It may seem a strange decision coming from someone who has to eat 6 times a day, but this is the 138kg sedentary bloke who wants to do an Ironman, so maybe not that surprising.


So I decided I would eat Christmas lunch, and then commence a fast. I thought ideally I would like to go for 5 days depending on how I was feeling, but that 3 days would be very beneficial, and if I was feel great and not losing my marbles by then, I could stretch this to seven days. By fast, I mean water only. Essentially zero calories, but I would take some electrolytes to protect against low salt, as I knew I would be drinking much more water than usual.


My goals in undertaking a prolonged fast were as follows

  • Prove to myself that I didn’t need to eat every couple of hours to survive
  • Reset my metabolism
  • Lose weight
  • Ageing prevention

Once I decided to do this, (about a week before Christmas), I did decide to do some preparation before jumping in the deep end. On the 23rd December, I didn’t eat between breakfast and dinner, which was about a 12 hour period. I then fasted through the next day until around 6pm, which was about a 22 hour fast. I found both of these periods very easy, and felt minimal hunger, and actually felt quite good. I then didn’t eat until lunchtime the next day. I had been given some rum balls on Christmas morning, and had them sitting next to me in the car on the way to Mum’s for Christmas Lunch, so I tried to feed them all to the kids, they ate a couple, but they kept talking to me for half an hour whispering “eat me, eat me”, so I did. There were about six left, so I got a got warm up into lunch. Lunch was pretty amazing, and I ate everything in sight, twice, so by about 3pm I was feeling completely stuffed, and decided that was it, time to get this thing started.

I should also note that I have been eating a predominantly plant based diet for the last 2 months, and had stopped drinking coffee about a month ago. I have really been trying to limit caffeine consumption. I think to a large extent I had detoxified my body prior to the fast, which mean I was not dealing with these withdrawals for the first couple of days. This definitely make things much easier.


Before I get started on the day by day account,  I’ll review the tale of the tape before Christmas. I had been steadily losing weight for a couple of months, and on the 15th December, weighed in at 128.3kg. I had my work Christmas do on Friday the 20th, and ate quite poorly there, but my diet had been spot on for the rest of the week, so I was pretty pissed off to weigh in at 129.4kg on the 22nd Dec. ( I try to only weigh myself every Sunday). I decided to weigh myself on Christmas morning to give me a baseline measurement, which was 127.9kg. I found this quite surprising, my obviously my body liked the idea of the time restricted eating of the previous 2 days.


Day 1

I woke up feeling good. I am normally not hungry in the morning, so it was no surprise that I wasn’t hungry on waking, despite not having eaten since 3pm the day before. I didn’t have my scales a mum’s so didn’t weigh myself. I had a peppermint tea at breakfast, and went for a walk with Mia to the park. I headed home, and had a pretty lazy day, watching a bit of the Cricket, and doing some work around the house. I felt a bit peckish around 4pm, but it was very manageable. I decided to have a beef stock cube in some water around dinner time. I think I was craving some salt, and more importantly flavour. I also took a magnesium supplement in water before bed, just to make sure I wasn’t getting to depleted. I had a little trouble getting to sleep, and woke a couple of times during the night, but other than that slept quite well. All in all, I found the day quite easy, and felt in good shape going into tomorrow.


Day 2

By the time I got up, it had been 40 hrs since I last ate. Once again, I wasn’t hungry on waking. I was interested to weigh myself, and the result was 126.1kg. That was a 1.8kg loss in 48 hours, during which I have consumed about 4000 Calories at Christmas lunch. I was pretty happy with that, particularly in that according to my scale (reasonable good quality bio-impedance scale), the entire weight lost was fat. Lean body mass had had not changed. There would have been alot of water weight lost along with the depletion of cellular glucose, so I need to take that with a grain of salt (craving salt again!) The rest of the day was pretty much like the day before. I did go for my usual morning walk, during which I do a few sets of pushups. Walking felt fine, and the pushups felt the same as usual. I went for another walk in the evening, and also felt fine. Around dinner time, I felt slightly light headed, but had another stock drink and magnesium drink and felt fine. 


Day 3

I felt like I didn’t sleep that well last night, but my sleep tracker said I had good quality sleep. I did go to bed a bit earlier than usual, so maybe I just woke up after my normal period of sleep, and struggled to get back to sleep. On waking, I did feel a little woozy, not enough to say I was light headed, but definitely a bit off. I got up, and went for my usual morning walk, including the sets of pushups I usually do. Maybe they felt a bit harder today, but not enough to be sure. By the time I had a drink of water, and been for my walk, I felt 100% again. I was not hungry. I wanted breakfast, but it was entirely mental. My stomach was not having hunger pangs and I certainly didn’t feel like I was starving. I was looking forward to weighing myself. I find the data side of this whole exercise fascinating. My weight was 125.1, which was 1kg less than yesterday. I was expecting something between .5 – 1kg per fasting day so that seemed about right. What was more interesting was looking at the body fat % (BF%) and the muscle mass % (MM%) comparing today and yesterday. Yesterdays result was BF 34% and MM 34.4%. Today was BF 28.1%, and MM 37.5%. Doing the maths on this gives a single day DECREASE in body fat from 42.87kg to 35.15kg, and a single day INCREASE in muscle mass from 43kg to 46.91kg. I can’t, and really don’t believe those numbers. I wish I had have had the time and money to get a DEXA scan pre, and post fast, but my home scales are all I have got. I think the direction of change is probably accurate, but there is something else going on metabolically, probably around water retention. I can understand the fat loss, as I would be quite fat adapted by now so metabolising much more fatty acids in the absence of any glucose in my system, but the increase in muscle mass is interesting. All the exercise I did was going for a walk, about 60 push ups, and some glue activation exercises, which I had never done before, Nothing I would think would encourage hypertrophy. It makes me really want to continue through to day 4 to see if this normalises, or if the trend continues.


I was feeling pretty good during the afternoon, so decided to go for a swim, as I usually do on a Saturday. I didn’t push particularly hard, but still did around 1.6km. I took a little bit of more rest between sets than I usually would, and swam a bit slower, and felt pretty good. After the swim, once I drove home I felt quite depleted, and like I needed a nap. I also felt quite heavy, my arms in particular feeling dead. By night time, I was feeling pretty exhausted, and had a nagging headache. I went to bed around 9PM, and was starting to think breakfast tomorrow would be a really good idea.


Day 4

I had a pretty average nights sleep, having found it difficult to get to sleep, and waking a couple of times, still with the headache. When I finally woke up for the last time a bit before 6AM, I felt surprisingly good. Perhaps a bit light headed when I stood up for the first time, but other than that, no headache or other issues. I was keen to see what my usual Sunday exercise would feel like fasted, so I decided to do that instead of having something to eat.


Before I headed out for my walk, I weighed myself again. Weight was 124.7kg which was a change of 500 grams. Once again the direction of the change in BF and MM was the same. All of the weight loss seeming to come from BF, and a very slight increase in MM.


My exercise was a 4.8km loop around Mt Lofty. I usually wear a Garmin HR monitor when I do this walk, so I was curious to see the difference between last week, and this week doing it fasted. This walk has a couple of good hills in it, so I have started setting a max HR of 140bpm for this walk to prevent myself pushing too hard. I think this makes for a better measure of the effect of fasting, rather than seeing how hard I could push. The walk itself felt great, and I wasn’t at all tired when I finished it. I could have done it again, but I wanted to be a bit cautious because of how bad I felt yesterday after my swim. I have put the stats from last week and this week below for reference. There was not much difference between the two weeks. About 2mins 20 sec difference in elapsed time. My average heart rate was a bit lower this week, which would account for the the difference in time. I didn’t push as hard on the flat, and downhills sections as last week, so the average HR and pace came down a little. In summary, I don’t think I lost anything at this level of exercise for having not consumed a calorie for nearly 90 hours.

I felt almost euphoric after the walk, and carried this through most of the day. I got a done, and got through the day quite easily. When 3pm passed, which was always going to be the time of day I started eating again, I barely thought twice about deciding to push on to day 5.


Day 5

Day 5 was always going to be interesting. The previous 4 days, I could be a bit of a hermit, staying at home, keeping myself busy and staying very much within myself. Today, I had to go in to work to receive a delivery, and would need to be there most of the day, waiting for it to arrive. I am always hungry at work, and when I am at my desk, I generally eat something every couple of hours. I was interested to see how this would go. It was also going to be incredibly hot, with 44 degrees forecast. I was going to have to move about a ton of cartons, while fasted, in that heat.


The day got off to a good start. I got up, weighed myself, and went for my usual morning walk. This felt fine, but the sets of pushups were definitely more difficult to get through. I didn’t feel like I had less capacity to do them, they just felt much more difficult. I weighed in at 123.3kg, which is 1.4kg less than yesterday. This was a big drop. It was quite hot yesterday, so possibly I wasn’t as well hydrated as the day before. This was the first day where I saw BF% increase slightly, and MM decrease.


I felt fine and switched on getting to work, and was quite productive. I was a bit light headed when I had to get up to walk around, but nothing concerning. The delivery driver waited until mid-day to arrive, so it was very hot and unpleasant by the time I had to do some labour. I took it fairly easy, which I would have done anyway given the heat. I certainly felt weaker than usual. Again, not in the sense that I felt a reduced capacity to do the work, but like I was having to push through a layer of lethargy to get it done. By the time I was done, and decided to head home, it was about 2.30pm and I was very much starting to ruminate about the re-feeding process that was about to commence.


Re-feeding
At 3.05, exactly 120 hours, 3 minutes, 49 seconds, 65 hundredths (who was counting), I had something to eat. I’d read some bad stories about difficulties with digestive issue after a fast, so decided to take it easy, and try some easy to digest food first. I had a handful of almonds and cashew nuts which I had soaked overnight to make them more digestible while I made myself a smoothie. I blended up some hemp seeds, dates, a banana, and some pea and hemp protein powder into a nice cold smoothie. This took me about half an hour to drink. Normally I would just smash it down, but just didn’t fell the need. I wanted to have dinner around 6.30, but was still feelling full. It was always going to be vegetarian and raw, so I made a small salad with baby spinach leaves, tomato and chopped carrot. A light dressing with lemon juice, avocado, and olive oil. I decided to take a risk, and have it with some of my home made hummus. Fortunately, there were no issues with digestion, and I felt fine going to bed.


Day 6

I want to document the couple of days post fast, as personally I was concerned what this would look like, and also to keep myself a bit accountable to not lapsing into a shark like feeding frenzy.


I had a poor nights sleep, struggling to get to sleep, and waking a few times during the night. I was up at 6.30, weighed myself, and went for my usual walk. The pushup’s this morning felt terrible. I got through them, but the burn was like nothing I had felt while fasting. The scales were interesting. I weighted in at 123.4kg, 100 grams more than yesterday. BF% had gone up significantly, and MM had fallen again. On order to put this into perspective though, if I go back to Christmas morning, the numbers were 127.9kg, BF 34.9%, MM 34%. This morning the numbers were 123.4kg, BF 30.1%, MM 36.4%. So it appears that during the course of the fast, I have lost body fat, and put on muscle. Again, these numbers come from a home bio-impedance scale, so the body composition data is not very accurate. The weight should be though. I was very happy with the weigh loss.


I really didn’t feel like breakfast, and I had plans to go out for lunch so decided to skip breakfast. I had Vietnamese for lunch, some spring rolls, and a bowl of Pho. It went down a treat, and apart from being quite full, I had no digestive issues. I had to go to the shops to get some food. I did grab a chunk of rocky road which wasn’t a great idea, but apart from putting me in a sugar coma, I felt fine. I had a very small salad around 6PM, watched a movie, then went off to bed.


Day 7

New Years Day. I woke up this morning feeling fantastic. I had my best nights sleep in ages, and was rearing to get out the door to go for a walk in the Dandenong’s. 


I did weigh myself first, but after today, I will be back to weighing myself once a week as I don’t like obsessing over these numbers. My weight was 124.5kg, so that was 1.1kg more than yesterday. Looking at the composition numbers, BF fell to 28.2%, and MM increased to 37.4%. I’m sure there is still some whacky metabolic stuff sorting itself out inside of me, so I will be interested to see how it has all balanced out after a couple of weeks.


I did my walk without having eaten, and will not eat until I go out to lunch with Mum today.

I think that is all for this blog post. Have a great New Near Everyone, and if you got this far, thanks for reading.


Key learnings

  • I don’t need to eat every couple of hours. This psychological barrier was the most important for me. Running a marathon doesn’t scare me, because I have done it before. Now fasting doesn’t scare me, because I have done it before
  • Fasting is a great way to lose fat. The nay sayers will cry that your muscle will waste, but in my case that was absolutely not the case.
  • Time restricted eating (TRE) is definitely worth a go. I am very interested in the weight loss before Christmas day, from a couple of days of TRE. I’ll definitely be giving this a go to see how it feels. I am thinking maybe 5 days a week for a start, with a four hour feeding window.
  • I stayed quite alert and well functioning mentally. I don’t think I would have any issues working fasted, making a repeat every 3 months much more achievable.
  • There is so much good information out there. Inform yourself, read articles, listen to Podcasts. If you wait for your Doctor to tell you this is a good idea, you’ll probably be dead first. 


Some great resources I have used
Dr Peter Attia https://peterattiamd.com/start-here/ I find his podcast The Drive to be very informative Rhonda Patrick https://www.foundmyfitness.com/ Also have a very good podcast. Has a great way of explaining the science Tim Ferriss https://tim.blog/2019/11/27/peter-attia-fasting-metforming-longevity/ This podcast with Peter Attia is really useful

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