Body fat % scales - trend

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themdt
themdt Posts: 1 Member
in Health and Weight Loss
Hi there! I have a Withings scale that provides my weight, body fat %, heart rate etc. From reading through some of the posts here, I understand that the BF% on such a scale is completely inaccurate and not a reliable measuring tool. However, I would like to know if the trend is accurate, so basically if last month I was at 26% and this month it’s 25.5% is it safe to say that I have decreased my body fat, irrespective of whether the actual % is accurate or not? Hope this makes sense. Thanks!!

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  • Muscleflex79
    Muscleflex79 Posts: 1,917 Member
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    no - seeing it change from 26 to 25.5 it is not safe to assume you have lost bodyfat because the scales are so wildly inaccurate - readings are affected by too many things (wet feet, what you ate/drank, sweat, etc.) that it is not wise to read too much into them. I suppose if you had a number of readings over time (months, years) and the numbers went down over a long period of time you could read into that, but not two random readings over the course of a month or two.
  • kuranda10
    kuranda10 Posts: 593 Member
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    My Aria scale is less than 1% off from the Dexa scan I had done. I weigh in the morning at roughly the same time. I don't get the wild readings everyone claims to get.
  • DX2JX2
    DX2JX2 Posts: 1,921 Member
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    I used to think that you could use the trends generated by the info but I no longer think that to be the case. Most of those readings can be impacted up or down by a ton of different factors at each weigh in and I've found that the variances are rarely consistent.

    Trends would mostly be meaningless given the random volatility of the numbers. Those scales are even more worthless than I originally thought.
  • DX2JX2
    DX2JX2 Posts: 1,921 Member
    edited October 2017
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    kuranda10 wrote: »
    My Aria scale is less than 1% off from the Dexa scan I had done. I weigh in the morning at roughly the same time. I don't get the wild readings everyone claims to get.

    I've never used the Aria scale but it is worth noting that even a broken clock can be right twice a day. It's the method of measurement that drives the inaccuracy and volatility, not the hardware.
  • jjpptt2
    jjpptt2 Posts: 5,650 Member
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    My guess is that if it's an actual trend over time, not just 2 or 3 or 4 data points, then yes... the trend would be meaningful as all the things that lead to variations in measurements would average out over time.
  • DX2JX2
    DX2JX2 Posts: 1,921 Member
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    jjpptt2 wrote: »
    My guess is that if it's an actual trend over time, not just 2 or 3 or 4 data points, then yes... the trend would be meaningful as all the things that lead to variations in measurements would average out over time.

    True, but the method to measure is so inherently inaccurate and volatile that it's got to be a really long trend. On order of 3-6 months at the very least.
  • AnvilHead
    AnvilHead Posts: 18,344 Member
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    Good read:

    https://weightology.net/the-pitfalls-of-bodyfat-measurement-part-4-bioelectrical-impedance-bia/
  • EliseTK1
    EliseTK1 Posts: 479 Member
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    Tacklewasher wrote: »
    I'm going to stick this up here.

    0iys99mva2bw.png

    This is my trend from Feb 17 (when I got my Withings scale) to today. It shows a decrease from ~36% to 29%. My weigh (trendweight as well) has gone from 264.6 to 224.6 in the same time period.

    I'm not going to suggest any reading is accurate, or that the 36% or 29% are accurate, but I think the trend is useful and shows that I have indeed lost fat over the 9 months.

    If I accept what this is telling me, it also shows my Lean Mass has dropped from 169.3 to 158.9 in the 9 months. So for ~40lbs lost, I lost 30 lbs of fat and 10 lbs of lean mass. Considering I wasn't lifting until August, I'm pretty happy with that.

    So to answer the OP, contrary to other answers, I think the trend (maybe not 1 month but 6 months or more) is useful despite the inaccuracies.

    Note that I do try to weigh daily in the same conditions (first thing after peeing).

    This is amazing. Congratulations!!! (I love visuals like this.)

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