19/06/2017 09:56 BST | Updated 19/06/2017 09:56 BST

Pros And Cons Of A Five Day Fast

There is more and more research coming out about the benefits of intermittent fasting. This research is starting to show there are a number of health benefits beyond simple weight control; what grabbed my attention were the benefits to mitochondrial health.

As you will read in the article above, new research and suggestions about eating habits are always accompanied by very strong, and generally opposing opinions. As the research around the benefits is becoming more and more compelling, I thought I would give it a try. My aim was to see if fasting was difficult and if the pros out-weighed the cons.

I started by researching the various fasting protocols and settled on the five day fast with 750 cal/day. This is the protocol recommended by Dr. Michael Mosley in his book The Fast Diet. It seemed to be less severe than the 3 day water fast, which is zero calories for three days.

The first step was to decide on what I was going to eat to get the 750 cal and have it all prepared. My aim here was to continue promoting good gut health with fermented foods and to ensure minimal insulin response. I therefore restricted macros to mainly fat.

  • 1 cup Kefir - 160 Cal
  • ½ cup Sauerkraut - 20 Cal
  • Bullet Proof Coffee - 230 Cal
  • 1 cup of bone broth - 40 Cal
  • Avocado - 300 Cal

When calculating the above, I was quite surprised at how little food is required to make up 750 cal. It's easy to see how people easily consume too many calories and why our population is becoming more and more obese. More on this below.

Results of Michael Betts 5 Day Fast

Image courtesy of TRAINFITNESS

Fast Day 1

Weight - 79Kg
Body Fat - 15.6%

First day was easy. I didn't do any exercise but had a lot to do at work so I didn't really have time to think about food.

Fast Day 2

Weight - 78Kg
Body Fat - 15%

The stats were motivating, although I was very aware that most of this would have been fluid loss. I was definitely hungry but found that a good, hard work-out in the morning stopped that. Then keeping very busy at work also helped. I worked longer hours so that when I got home, all I had to do was shower and go to bed. I didn't want to be tempted to break the fast.

Fast Day 3

Weight - 75.6 Kg
Body Fat - 14.2%

I had read that day 3 was the hardest, and it's true. To say I was hungry was an understatement. Again, a solid workout stopped me feeling ravenous for a while, but I was constantly aware of the hunger pains. Sleep that night was also not great. It was very light and I woke many times, each time struggling to get back to sleep.

Fast Day 4

Weight - 75Kg
Body Fat - 14%

The stats were very motivating; I had lost 4 kg so far. Although some of it would have been fluids, there would definitely have been fat loss happening. Feeling tired, I still made myself workout, it helped with not feeling hungry as did keeping busy. Day 3 was definitely harder than day 4 which may have been due to the realisation that I was over hump-day and the finish line was in sight.

Fast Day 5

Weight - 74.1 Kg
Body Fat - 13.3%

IT'S THE LAST DAY; I was so happy. Just the fact I had done 4 days already and I knew the re-feed was so close made day 5 easy. I felt hungry but it was easy to ignore. My workout was good and overall I felt great. I have always been goal driven so completing the fast was motivating enough. Plus the results were better than I expected.


I lost almost 5Kg and dropped 2.3% body fat according to the biometric scales, which can be quite inaccurate. I take that measure with a "grain of salt". Since then, my weight has fluctuated between 74-76Kg so I would like to believe I did lose a couple of kilograms.

Did it improve my mitochondrial health? If the research is true, yes. But that's something that, after regular fasting, only time will tell.

I did enjoy the experience and it is something that I would do again. There are a number of points the exercise highlighted:

  1. If you are overweight and you want to lose weight, you can. Restricting calories, relevant to your needs, is all you need to do. Having said that, it does take will-power and awareness. You have to want to lose weight and you have to stick to the plan.
  2. We don't need that much food to meet our daily calorie requirements. For a few days after the fast, I calculated the calories for various meals I had. One breakfast of 2 sausages, an egg and two slices of sourdough bread came to around 800cal. That is almost half my daily calorie requirements in just one meal. Depending on your size and gender, your body will require between 1500-2500 calories per day. That is really not that much food. Food is everywhere and we have been rightly or wrongly told to eat at least three meals a day. Research is showing though, we don't actually need to eat that much.

The pros for me were that it worked, I lost weight. The cons, it took quite a bit of will power. Do the pros outweigh the cons, I say, most definitely.

My Advice

If you are thinking of doing a fast, make sure you are prepared. Have all the food you need ready so you don't have to go out looking for it.

Keep up the workouts and train hard. I found a high intensity workout was a great way to curb my hunger. People asked, "where do you get the energy from if you don't eat"? My answer, "Unless you have 0% body fat, then you have all the energy you need stored away on your hips, thighs, belly, back, wherever you have those fat deposits". Fat is your body's way of storing energy.

My last piece of advice is to keep busy. Plan your 5 days so that you have lots to do. I don't think I would have survived if I did this over a weekend. Monday to Friday was easy as there were plenty of distractions and lots of work to do. Don't give yourself time to think about food and 5 days will fly past.