I’ve always had weight problems. Only in recent years has it gotten under control and landed me comfortably in the overweight category, like I was last summer. It wasn’t life threatening but it wasn’t ideal either. For the most part it was stable, and I was stable living with it. Yet it only took one comment from a work colleague, one with harmless intention, to change my mind on that.

Sometime in early August, I same across the Hacker’s Diet and finished it within a week or two. You can find the full text available online. The book is directed towards engineers and approaches the human body like a machine, one with inputs and outputs. A machine that you can tune to get the results you want. It’s quite contrary to other diet books that suggest slow and methodical lifestyle changes. Instead it asks you to measure everything, monitor consistently, and reassess constantly with the information you have. It’s a feedback loop that, so far, has been effective.

The Eat Watch

The eat watch is the centrepiece introduced in the book. The premise is that some of us are predispositioned to eat more (or less) than our body needs because we don’t receive the “full” (or “hungry”) signal in time, or at all. The eat watch is an imaginary accessory that lights up when you should eat and turns off when you shouldn’t. Hence, you’re relying on your watch rather than your body for the information.

In reality, the eat watch manifests itself in calorie counting and eating prepared meals. The goal is to count everything. As noted in the book, eating a few slices of cheese in the evenings can amount to a weight gain of 0.6 kilograms per month. Being aware of seemingly-inconsequential snack-eating is very powerful. If you monitor everything then you don’t need to think about if you’re overeating or undereating.

I monitored calorie intake with prepared meals. Thankfully I don’t get bored of eating the same food day in and day out. If you do, that’s okay too. You just need to be aware of the calorie contents of the different meals. Averaging them over the weak may help ease calculations. All you need are the daily totals of your calorie intake, and weekly if you want to plot trends.

Burning fat by undereating

This is controversial. Every single friend, family member and physician/nutritionist/personal trainer I have ever spoken to has recommended against this. They say that going under your recommended calorie intake by any significant amount will force your body into “starvation mode” and that once you stop you will put all the weight back on, because your metabolism will be so slow. On top of that, you’ll be miserable, unproductive at work, always tired, and unable to get results from exercise.

I have found most of this to be untrue. Let me clarify what my significant amount was. I’m a 179cm-tall 24-year-old male. From online research, talks with nutritionists, and my own experimentation, I should be eating around 2400 calories per day to maintain my weight. Instead, I was 1600 calories some days and 1200 calories other days, by skipping dinner, during the peak of this diet.

This, in my opinion, is the best lesson in this book. I never would have dared attempt a calorie deficit that large prior to reading it. The experience was not nearly as bad as people suggest. I was not miserable, because I was working towards a goal that was important to me, and I was never at risk of feeling guilty from eating. I didn’t feel less productive at work and nobody every confronted me about it. I was no more tired than usual, sometimes less so, which I put down to not feeling as bloated.

Maintaining your metabolism is tricky and you need to be careful. Thankfully the book introduces a plan for that as well.

The Five Basic Exercises

Back in the 1950s, the Royal Canadian Air Force developed a training regime for pilots stationed on remote air bases that wouldn’t have had access to gym equipment. The regime needed to rely exclusively on bodyweight exercises and be able to keep someone in optimal condition in minimal workout time. The regime was called 5BX and you can find the plan online.

The book contains its own plan modelled after 5BX, but I decided to stick with the original. I think the details of the plan are less important than just doing exercise regularly, preferably everyday. 5BX can be completed in 11 minutes. I did it every morning just after waking up. On top of that, I went to the gym on Saturdays and Sundays and do cardio and weights. With that level of activity, my metabolism had a hard time slowing down.


The best test for a slow metabolism is the holiday season! I stopped heading to the gym around mid-December, but I continued with my 5BX workout everyday. And I was eating whatever I wanted. Granted, I wasn’t reckless, and rarely went over 3000 calories on a given day, but I stopped following my eating plan and relaxed my constraints on the types of food I was allowed. Cake, crumble and cranberry sauce were all on the table.

This was a conscious choice. When I started the plan back in August, I was about 87 kilograms. I wanted to be 72 kilograms, which seemed like a good weight for my height and build. I decided to aim for that by Christmas. I was aware that this goal was ridiculously ambitious but worked towards it anyway. I needed to lose 15 kilograms and that would give me about 15 weeks to do it. One kilogram of body fat is equivalent to 7700 calories, meaning I would need to have a daily calorie deficit of 1100 calories, so a daily calorie intake of 1300 calories on average. If I had a perfect run, that is certainly possible to hit.

Hacker's Diet Five Months In Results

I didn’t hit it, but I made a big dent. This is a plot of my progress. The blue line is my actual weight as recorded every morning. I started the eating plan in mid-August and started weight measurements on the 27th of August. The two periods of flat recordings in late September and late November are when I was on vacation and didn’t have access to a weighing scale. The red line is an exponentially smoothed moving average with 10% smoothing. Provided the red line is declining, weight is decreasing. The red line helps smooth out the variance present in daily weight measurements and is meant to represent the true weight.

My weight certainly went up in December, but the amount was marginal. Once January came around, I quickly recovered from it. I’m confident that the weight increase was down to increased food intake, not a change in my metabolism. I started back at the gym on weekends in early January and was able to perform at the same level on weights, and near the same level on cardio. I certainly felt my chest got weaker over the holiday period because I wasn’t running, but don’t think I lost much muscle mass. I put that down to 5BX, which in many ways saved Christmas!

Losing that final third

Maybe I should be 72 kilograms, maybe not. I still think there is potential in this plan, but I am now firmly in the period of diminishing returns. My BMI shifted from the middle of the overweight category to the upper part of the healthy weight category during this chapter of the journey so I definitely consider it a success and perhaps even complete.

Perhaps for the first time, weight is not the goal. I have began looking into body weight strength training in greater depth. 5BX gave me a different way to measure strength training that I didn’t have before, namely the number of reps I can do. It’s a different mindset to using exercise machines where the weight can be arbitrarily adjusted to be challenging. Sure it feels good to be able to chest press more weight, but being able to do just one more press-up has given me more satisfaction.

The recent Work It Out Humble Bundle contains a lot of food for thought. Included were a few body weight strength training books, diet books and mindfulness books. I’ve began reading Body Weight Strength Training, which contains a workout plan in a similar vain to 5BX but across 40 different exercises. I’ve spent the last few weeks getting used to them all. Now that I’m a healthy weight, I want to focus on building functional strength rather than weight loss. There is a lot to think about where to go from here, but I’m happy about the progress made thus far.