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How I lost 13kg of body fat in 90 days

I get asked a lot to write about my experience with intermittent fasting and how I shred my body fat. Now with a few weeks of holiday I’ve finally found a spare hour with my laptop to finish this post for those of you that have been waiting for it. So here goes…

Why I decided to lose my body fat

First, let me say that I don’t really care too much about what I weigh. I care about my health and how I feel about my body, and so my body fat percentages, blood work, and my cardiovascular fitness, are the measures of health that I use.

Most people have probably never considered me to be fat, but at my peak I weighed around 87kg. Given my height, that put me at a BMI of 29.8, which is high on the overweight spectrum (and yes, I know BMI isn’t the only metric, but it is a good one).

At the time I was living on the Gold Coast and commuting to Brisbane every day for work, often leaving at 6am and not getting home until close to midnight, plus averaging a hotel in Brisbane one night a week. I had completely lost focus on any form of exercise, telling myself the lie that I didn’t have time (the reality is that everyone has the same amount of time, I just prioritised other things).

I was skinny fat — meaning my body fat didn’t visibly sit on my gut (well, maybe not, see next paragraph), but rather it was more visceral fat, distributed across my body and surrounding all my organs, which I’ve been told is way more dangerous in terms of health consequences.

Ultimately it was a photo that prompted me to action. One day I got home from work, opened the letter box and read the newsletter from my local Brisbane council member. There was a picture of me with her on the front cover of the newsletter, and I had a large fat belt line clearly visible around my waist.

I remember my thought in that moment: that is not me! There was a massive disconnect between how I saw myself, and how I actually was. (I’ve since seen other photos of myself from that period and I almost don’t recognise myself.)

That photo prompted me to take action. But what helped me to maintain action (consistency of action is the key) was my kids. First, I want to live as long as I can for my kids. Second, I want my kids to have a great attitude and habits towards health, and I believe this is best achieved by leading by example.

Why I chose intermittent fasting

My sister Liz is a GP. A very good one. She regularly sends me the latest research on anything related to health and well being. But what I love the most is that she proactively adheres to incredibly high standards of personal health through diet and exercise.

Liz shared the latest research on intermittent fasting, and recommended a book to me: “The Fast Diet: The Simple Secret of Intermittent Fasting: Lose Weight, Stay Healthy, Live Longer” by Michael Mosley and Mimi Spencer.

I purchased the audiobook via Audible and listened to it at the gym. I consumed the whole book in a matter of a few days, and then did some more online reading of intermittent fasting. I also asked friends on social media and discovered a lot of my friends with very healthy weight and body-fat ranges were all massive advocates and regular practitioners of intermittent fasting.

So I decided to give it a go.

The premise

Let me pre-empt the next bit by saying I am not a doctor or a dietician. I have no idea what I am talking about here except to the extent of what I have read and what worked for me.

Nonetheless, the basic premise of fasting, as I understand it, is that in order to burn body fat, you first need to put your body into a state of Ketosis. It’s a pretty simple concept that goes loosely like this: If you want to burn fat fast then your body needs to have run out of other sources of energy to burn first.

Put another way — what matters more than what you eat is when you eat.

Like I said, I have no idea what I am talking about, so best to read up on it if you want to know the details.

What I did

What worked for me was a long fast of 18 to 22 hours per day, and then one short eating window of 2 to 6 hours, repeated everyday. I would skip breakfast and lunch, and just eat dinner.

Dinner time was my only meal-time. Normally I would eat somewhere between 6pm and 9pm (depending on whether I ate with the kids). On weekends I would often break my fast and just be normal for the two days, then resume fasting on Monday.

As much as possible I had as close to zero calories in my fasting window. That meant replacing my normal flat white with a short black (which later became a green tea, then later just water).

What I ate

Based on my weight and fat-loss goal, I calculated my calorie-deficiency targets (there are lots of tools online to help you do that, like this one). I set a goal of consuming no more than 1500 calories per day. I then kept track of my calorie consumption using the My Fitness Pal app.

By the time I got to my eating window, I would be craving vegetables. Lots of vegetables. I don’t normally crave foods, particularly vegetables. But on my fast days, I could eat kilograms of grilled veges.

Most nights I would eat some form of lean meat (steak, chicken, salmon) with grilled vegetables or salad. I often also had ice-cream (with or without an apple pie) for dessert. I still had a glass or two of wine, even though it just added calories with no nutritional value. And yes, I still ate cheese and crackers (a love of my life).

Really, I could eat whatever I wanted in that window of time, but my interest in carbs completely disappeared. I didn’t want to eat any form of breads, pasta, or biscuits.


You have to measure something if you really want to change it, otherwise our brains fudge things. Don’t believe me? Compare how many times you think you went to the gym last month with their actual record of your attendance — it will likely be very different.

During my fasting period I kept a spreadsheet tracking my eating and fasting times, my calorie consumption (my daily total from My Fitness Pal app), my alcohol consumption, my sleep, my weight, and my exercise. That may sound complicated, but it really takes less than 30 seconds to fill out each day.

I also took ‘before’ photos of myself, with all the flabby bits, in the worst possible lighting. Nothing like having that visual to keep you motivated to improve yourself.

Plus having the results there and seeing the changing in numbers is very motivating. Because looking at yourself in the mirror everyday you simply don’t notice the longer term changes.

How I felt

Everyone asks: didn’t you feel hungry? Yes on the first fasting day each week, and usually around 2pm, but other than that I was fine. I learnt to expect my 2pm hunger craving and just push through it with a walk and water to distract me.

During the fasts I actually felt more awake, like I had more energy, and could concentrate better. I didn’t have any of the normal ups and downs of the day — I didn’t feel tired in the afternoon — and I slept better at night.

But on the downside I did notice that I made more spelling mistakes when typing, and occasionally wrote sentences that didn’t quite make sense. Which now that I say that, it does sound kind of bad. But in overall work output, my tempo and outputs were definitely up.

How I managed social events

The beauty of intermittent fasting is that you can totally adjust it as needed. So if I had a work lunch or social event on, then I would simply break my fast that day and eat like normal. Or shift my fasting window to start or finish earlier.

The flexibility is actually what makes intermittent fasting so effective, because it means you can adjust it into the reality of life, making you adhered to it much more consistently than other diet formats.


Much of the literature said not to do strenuous exercise when fasting, or to avoid heavy resistance training, high-intensity cardio, or similar. Rightly or wrongly, I ignored that (I only know one speed: faster).

I actually maintained heavy resistance training and alternating cardio training every day, whether fasting or not. (I exercise in the morning for a lot of reasons, but mostly because anything done first thing in the morning is more likely to get done consistently without distractors; plus morning exercise lifts your metabolism for the day and puts you into a peak mental state).

I signed up for two weight-training programs with www.kinobody.com and also completed one of their 12 week challenges. Again, what I like about their programs is that it is insanely easy to follow and adjust into the reality of life. I still maintain an adapted version of their routines now.

My results

I had body scans and blood tests done pre- and post- this period so I could compare the results.

I lost 13kg of body fat in a 3 month fasting window. My skin was noticeably cleaner too (particularly the skin on my elbows, which is now smooth!).

I’ve lost more fat since, and put on lean muscle mass as well. My body fat is now down to 13%, and my BMI now sits at 23.9, well within the healthy range.

But perhaps more importantly, all my blood work levels and my blood pressure have improved massively, and are all now sitting pretty much on perfect levels.

What I learnt along the way

  • Everyone has an opinion on intermittent fasting. Almost everyone who is positive about it has tried it or still regularly use it, and almost everyone who is negative about it has never tried it. (Aside: that is always my filter of whether or not to listen to someone — have they actually done what they are talking about?). Lesson: if you do give intermittent fasting a go be prepared to get lots of questions and commentary from others.
  • I found it much easier to do extended fasts every day, than to do the 2&5 intermittent fasting format. For me, it would take one to two days to transition back to fasting days where I didn’t feel hungry during the fasting window. Lesson: it was easier for me to stay in that state than to constantly break fasting days and then return to the psychological battle for working back into fasting mode.
  • I quickly recognised that far too many social activities and business meetings revolve around food. From simple things like meetings over coffee, to catering at events, to social dinners, BBQs and lunches. Lesson: let’s just have more straight work meetings without food, or have walking meetings. For social events, let’s do more activities together other than eating and drinking.
  • When you are fasting you suddenly notice how much advertising there is for food, particularly junk food. Plus the unhealthiest food is the cheapest and most readily available. It is almost criminal.
  • If I eat any carbs — particularly white bread — then I will feel hungrier sooner, and crave more sugar-rich foods. Lesson: avoiding carbs and sugars massively helps me control my hunger and cravings.
  • I didn’t miss my morning coffees as much as the moment itself. I’ve since realised the importance of morning routines in establishing a peak mindset for optimal performance.
  • Water is the answer. Lesson: drink more water.
  • Exercise, even just walking, is great for staving off hunger pains.

Final thoughts

Intermittent fasting isn’t for every one.

But just like everything else in life, shredding body fat is simply a decision followed by consistency of action. Commit, then do. Or if you are like me, just do first because by then you’ll be committed.

[Aside: there are recent studies now suggesting that even just your thoughts can transform your body.]

Shameless Peak Persona plug

While we don’t cover diet or weight loss in our Peak Persona programs, we do cover a lot of techniques for getting yourself into action mode (engineering your life for more “do” and less excuses). Feel free to check those programs out if that sounds valuable to you.


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