Measurement and variation

One of the things about dieting is that you end up having to weigh and / or measure yourself quite a lot. My relationship with scales is almost as complicated as my relationship with food, and the tired old bathroom scales we had at the start of the year had a number of flaws.

  1. My eyesight isn’t really good enough to read them accurately
  2. The reported weight varies a lot – you can weigh yourself four times in quick succession and get answers that differ by up to 3lb, so the weekly weight check becomes more of an average estimation
  3. We suspected (based on intermittent use of other machines) that the scales were weighing light

So I purchased a new shiny set of digital scales from Argos. These have a readout which doesn’t vary even if you do step on and off the scales 10 times, and which is legible from a distance of 5 foot 2 (the approximate distance between my eyes and my feet).

There is always going to be some fluctuation however – weight does change daily, based upon a bunch of factors which will be obvious to anyone who’s ever had to try and lose weight. So in order to calibrate the scales with respect to eachother, I used them both for an extended period (11 days). The graph below shows this measurement fluctuation over time, by plotting change in weight across both machines. The faint line is a moving average over a 3-day window.

chart (2)

The delta between the two measurements had a mean of -7.022lb, which shows that the old machine was indeed weighing light. Whoops[1].

The new scales also measure fat%, bone%, and water% presumably using some kind of conductance (they have metal plates for your feet and instructions not to use if you have a pacemaker). The fat% and water% measurements vary quite a lot, and don’t seem to have a trend yet, but I will monitor them over longer time periods and update accordingly.  Bone% didn’t change at all during the 11 days of recording everything, so I guess that’s reliable.


[1] For the progress graphs on this blog, a 7lb increase will be applied retrospectively to old-scale measurements from earlier in the year.

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