It’s been about 4 months since I started seriously losing weight and hitting the gym, something I always wanted to do but never had the motivation for. But then I got it: I went through a bad break-up that made it feel like my life was over and I felt like I had to change in any way I could and fix the things I was not super happy about in my life. So that’s where the motivation — the critical ingredient — came from: I had finally had enough, which is quite a magical moment and detailed in a really nice article by Kris Gage here on Medium.

What I did to lose fat was simple, as outlined in my previous post. I can also recommend the excellent fat loss article on Physiqnomics which goes into much more detail than I do.

And as I embarked on this intense new journey, being the nerd that I am, I wanted a way to keep track of how I was doing. I wanted to avoid losing muscle, or even add some, as I was dieting, which is feasible but not easy.

The result of that was a spreadsheet that has served as my fitness dashboard since then, which gives me a clear view of my progress. A copy of that spreadsheet is available here, but you might need to adjust it for your own purposes once you understand how it works.

Step 1: measure consistently

Using it looks like this: every 3 days, I plug in the body measurements in the white columns on the left, which include caliper skinfold measurements and tape measurements of my body to assess subcutaneous fat and also muscle size. The yellow and orange columns use these measurements to tell me my body fat percentage (based on the average of 3 different formulas, for better accuracy) and thus how much total fat mass (FM) I have and how much lean body mass (LBM). Any change in LBM is likely to be due to a change in muscle mass, so we can use them as synonyms here.

Step 2: use custom indexes to measure what you care about

Next, I have put together a ‘fat index’ and a ‘muscle index’, which basically track the change in FM and LBM in a simpler way, by normalising the data to start at 1.00 and then change from there. For example, divide every fat mass result by the initial value (14.5 kg in my case) and that will give you a series of values starting with 1.00 and decreasing as fat is lost, down to 0.53 now. This makes it easier to compare two indexes measuring different things in a chart, and it has the advantage of being customisable: you can combine several such indexes by calculating a weighted average of their values where what you care more about has a higher weight than other things.

I customised the ‘muscle index’ in the following way. Since LBM has been decreasing a bit with the fat loss recently, but I have been getting stronger and stronger and my muscles seem visually larger, it seemed like just looking at LBM doesn’t do the whole thing justice. So I added the tape measurements of muscle size in areas I care about (chest, arms, shoulders mostly) into the ‘muscle index’, and the resulting chart then corresponds to what I see visually: a slight increase as I’ve gotten stronger over time (looking at my 1RPM for the bench press, for example).

While you wouldn’t find such a customised index in a scientific paper usually, you could argue that it gives a more faithful picture of what I want to measure, which is not just ‘how much do my muscles weigh?’ but actually ‘how much muscle do I appear to have visually?’ while remaining systematic and objective (because it’s tape measurements).

An additional data source that could be included to give an even more accurate picture would be actual performance at the gym (1RPM figures) over time for certain exercises. At that point, if your index is a composite score made up of a third of LBM, a third of muscle size, and a third of muscle strength, you can be pretty confident that it’s the most accurate look at your progress imaginable, and it can show you in precise numbers whether your progress is speeding up (due to some new supplement, new routine, or another lifestyle change) or slowing down.

The result of all of that is this chart, which shows that I have indeed lost fat, rapidly at first then more slowly, and increased muscle slightly during this diet. And since we want muscle to go up, and fat to decrease, we can also look at the difference between the two indexes (just subtract one from the other) as a synthetic progress indicator, since we want them to diverge as much as possible, the goal being zero fat and huge muscles. That is what I’ve done below.

So this progress index will keep going up as long as I either lose fat or gain muscle or both, but crucially it will not increase if I gain muscle while gaining lots of fat, for example. You can also see that the progress achieved is levelling off after the quick initial results (the green bars getting smaller) which is to be expected. Once the green bars turn negative, I will know I need to be careful or change something.

The next phase will be, as soon as I hit 10% body fat, to get into a small caloric surplus to start building muscle more seriously. At that point, most of the progress should come from muscle gains, not fat loss, and I expect the muscle index to increase more quickly at that point. If the chart shows me something different, I will quickly know that what I do is not working and that I need to adjust something, and I can objectively measure my rate of progress in both areas, and in the combined progress index.

You could even imagine looking at the rate of progress and correlating it with other metrics — hours of sleep per night, stress level (as evidenced by heart rate variability or resting heart rate) — to see how they impact my body.

Note: Of course, this method of creating indexes to normalise data, and then to combine several indexes into one that is weighted based on the factors you personally care about, is a great tool for any quantified self project and infinitely adjustable. That’s the beauty of it!