what are you made of?

Apart from the sugar, spice and all things nice, I wanted to know what else I was made of. I have always used scales till now, but they are very limited and can only tell you your mass. They can’t tell you how much of that is fat, bone, muscle or brains (erm).

While MRI is able to do this, skin fold and girth measurement is a more accessible, non-invasive option to get a rough estimate of your body composition. It involves taking measurements of your skin folds at different sites on your body using skinfold calipers. This can then be used as an indicator of body composition on their own, or plugged into one of several equations used to calculate body fat.

It is not perfect, you may never know what your exact body fat percentage is (really, it’s not so important), but it can provide a useful bench mark to track changes in your body over time and observe the effects of diet and training.

To get the most accurate readings, have them taken by someone qualified (of course). If you are taking measurements to track changes over a period of time, try to have the same person take them so there is consistency in the way they measure you up and the way they take the skin fold pinch.

Lucky for me, a colleague of mine is qualified (accredited by ISAK) to take these measurements, and to help him keep his eye in I generously donated my body for him to practice on.  I know, too kind… well, it would be, if I didn’t have an ulterior motive. I wanted to conduct a little experiment on myself!

The story

Last year I learnt I would need an operation and I would have to stop exercising for at least 4 weeks after. Esh, 4 whole weeks! So, I wanted to know what would happen to my body composition after the 4 weeks of not training, and the effect of reintroducing my body to exercise again.

I had my body composition measurements taken a month before the operation, 4 weeks after the operation before I started training again and finally again three months after.

It should be noted that my enforced rest was mostly over Christmas. I ate all the pies.

The method

For each session, my height and weight was measured. Eight skin folds were taken at the triceps, subscapular, biceps, lilac crest, supraspinale, abdomen, front thigh, and medial calf. Girths were measured for a relaxed arm, a flexed-tensed arm, the waist, glutes, and calf. Follow this link for a more detailed description of the sites.

I shall now present the results of the weight measurements, sum of the eight skin folds, girth measurements and discuss the changes in body composition.

The results


55.1kg before operation

54.5kg after enforced rest

55.33kg after resuming training.

Sum of eight skin folds:

85.8mm before operation

95.4mm after enforced rest

89.6mm after resuming training

Girth measurements

68.1cm waist; 93.1cm glutes; 26.1cm arm relaxed; 26.3cm arm flexed and tensed (before op)

67.8cm waist; 91.2cm glutes; 24.9cm arm relaxed; 25.3cm arm flexed and tensed (after rest)

67.1cm waist; 93.1cm glutes; 25.7cm arm relaxed; 26.3cm arm flexed and tensed (after training)

The discussion

Before and directly after operation

Well, I lost weight while not exercising and eating pie, but as I said at the beginning, this doesn’t mean anything on its own regarding body composition! Based on the sum of skin folds combined with the changes in girth, it can be concluded that my body fat increased and muscle decreased. Check out the relaxed and flexed arm girths, there is a difference of a 1 cm for the flexed arm. There was no difference in the sum of skin folds for the arm so that must all be muscle loss.  This implies the loss of weight is directly linked to the loss of muscle, since fat weighs less than muscle, even though the fat increased.

After training resumed

My weight went back up, in fact slightly more than before! However, the sum of skin folds has gone back down, although not quite to the level it was at before the operation. Interestingly the girth of my waist has reduced even more than it was before the operation, although the girth of my glutes has gone back up again to exactly where it was before. Also, the relaxed girth of my arm has gone up as well as the flexed girth. This implies muscle has gone back on.

In the greater scheme of things, not much has changed. I am now carrying a little more fat than before my operation (that’s 3.8mm distributed over my whole body, i.e. like, nothing) but more importantly, and it looks like I have managed to build up my muscles again.

All these changes are tiny, and this is not even taking into account any measurement error, or the bagel I ate just before. But it is interesting to see how changes in lifestyle can change your body composition in a very short time.

The body fat %

You may noticed I have not talked about body fat percentage. OK, so let’s look at 3 different calculations to estimate my current body fat percentage, Jackson/Pollock 3 Caliper method (JP3), Jackson/Pollock 4 Caliper method (JP4), and Durnin/Wormersley Caliper method (DW). I have used the online calculators you can find here.

17.41% (JP3); 16.88% (JP4); 23.16% (DW)

And they are all different, super different! Which estimate is most reliable? I don’t know, the equations used to calculate them are based on anthropometric data gathered from a generalised population. For the best estimate you need to use the one that is based on people most similar to you.

Age has also been factored in. Let’s knock 5 years off my age:

17.10% (JP3); 16.73% (JP4); 21.05% (DW)

Now I have less body fat, but my skin fold measures were all the same! It may well be true that for a generalised population body fat will tend to increase with age, but my measurements are still the same. The calipers do not know how old I am! Maybe they are assuming as you get older an increase in fat around the internal organs. To know this, far more investigation into the calculation and assumptions made is needed. This does, however,  demonstrates the pitfalls of trying to pin down body fat percentage using an equation.

From what I have seen, the most reliable measure is a comparison of skin folds from one time period to another. In fact, the sum of skin folds is often used, as shown here, precisely because of the errors using calculations. They use 7 sites. If I add up mine I get: 75.8mm. According to this table it puts me in the ‘excellent’ normal range and ‘good’ athletic range.

The conclusion

If you want to know how exercise, training, or diet is really affecting your body composition, throw away the scales and get your skin folds measured. It will tell you so much more than just your mass. Do it over a period of time and track your diet and training. Has it made an impact? What does it mean to you regarding the success of your diet/training and what impact has it had on your sporting performance?

This was an interesting experiment and I have learnt a lot in general about body composition, measurements and the like. However, I am an average joe, not a professional athlete, so all this is over kill. In the end, none of these figures makes me stronger, fitter, more powerful, or faster. Just as they don’t make me a better climber, less sacred to take falls, or perform better in cold weather.

More important than any of this is: to have fun with your sports, enjoy training, eat good wholesome food (with treats), and stretch and relax like a cat on a sunny afternoon (if someone will rub your tummy, all the better).

Be well!


4 thoughts on “what are you made of?

      • Best way is the water displacement method. Expensive to say the least! Your numbers look good but they are just numbers…Your overall well being and frame of mind are spot on!!!

      • Eureka! I hadn’t thought about that, excellent point, thank you. I imagine you would need a fair sized tank and a waterproof set of scales (for the splashing about)! they are indeed just numbers 🙂 fun experiment though, since i had to stop training anyway!

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