4 ms·

Hydration and other factors affect accuracy of impedance body fat estimation. So consistency is key, like measuring at the same time in the same conditions (for

Hydration and other factors affect accuracy of impedance body fat estimation. So consistency is key, like measuring at the same time in the same conditions (for myself, after waking and before any consumptions of food or water) daily. Still, absolute measurement will not be as accurate as DXA, hydrostatic, skin calipers, etc. However, for relative changes over time when consistently measured, impedance works just fine (trending upward or downward). I'm very skeptical of their claim that the photo measurements are more accurate than other means, but perhaps they've done massive validation of their methods and have achieved adequate reliability and validity.

parliament32 6y ago
>for relative changes over time when consistently measured, impedance works just fine Agreed, but for change over time it's just as accurate as skin calipers... which don't require an investment or subscription service.
- calvano915 6y ago
  While skin calipers are most affordable regarding equipment, the reliability is poor unless the person measuring is very consistent (well-trained and/or experienced for consistent pinch/folds). Calipers also will be inconvenient and possibly unaffordable for many because access to the person measuring is necessary whenever you want an updated measurement. In my view, impedance evens out with calipers because of the convenience of impedance measurements over time. I just stand on the scale for a few seconds every morning, and I have stats synced that give me a good enough idea of my status (bonus for the added understanding of my hydration which calipers won't do). There's no cost or subscription for my scale aside from initial purchase (Withings aka Nokia Body Cardio), and it is regularly available for as low as $99 on sale. So after a couple years and hundreds of measurements the cost is negligible given the benefit. If I had someone regularly accessible to do caliper measurements, I would have it done to compare regularly but still continue with impedance because it's so convenient to do and track.
  - parliament32 6y ago
    It's still useless if the data is garbage, which it really is. I had DXA scans done every half year for the last few years, and I've owned a few smart scales in that time (first Fitbit, then Garmin). DXA has shown me consistently dropping bf% (17.8%, 15.0%, 13.1%, 11.2%) while the scales (taking monthly averages) are all over the place (10.1%, 11.1%, 11.6%, 10.0% for the same months the scans were taken in). Impedance can show you a ballpark (and we're talking a wide, 10%ish ballpark) of where you are, but honestly you're probably better off just looking in the mirror and comparing to images online. I only mentioned calipers because they'd at least show you trends, which is where impedance seems to fail. Impedance is simply a poor way to measure bf%. Hydration might be a different story though. I'd recommend you do yourself a favor and just spend the $100 annually to see where you're at.
    - calvano915 6y ago
      I've had better experience with the Body Cardio scale. Though I haven't validated against other measures, I believe the body fat percentage is accurate enough based on my subjective opinion (it has not been generous to me like another poster's experience). Research has determined that impedance can be +/- 4% from actual in optimal conditions and my scale seems to fall close enough within that range. Regardless, I use it for all the variables tracked. I look at body fat percentage but body weight is ultimately the value of concern. I don't agree $99 a year is a good value just for bf%, because I do agree that visual impression means more than a specific number. The subscription cost for Amazon's service may be a great value (privacy concerns aside) if their photo algorithm is within a couple points of DXA or hydrostatic.
      - parliament32 6y ago
        >The subscription cost for Amazon's service may be a great value if their photo algorithm is within a couple points of DXA If it's accurate enough, I definitely agree. I'm looking forward to testing it out once it's available; since I'm one of those data nerds with actual ongoing DXA results, I'll be able to compare the two accurately. Although, pessimistically, I think if they had proven results within a few points they'd be a lot more quantitative in their marketing rather than the ambiguous language in the posts referenced above.

parliament32 6y ago

>for relative changes over time when consistently measured, impedance works just fine Agreed, but for change over time it's just as accurate as skin calipers... which don't require an investment or subscription service.

calvano915 6y ago
While skin calipers are most affordable regarding equipment, the reliability is poor unless the person measuring is very consistent (well-trained and/or experienced for consistent pinch/folds). Calipers also will be inconvenient and possibly unaffordable for many because access to the person measuring is necessary whenever you want an updated measurement. In my view, impedance evens out with calipers because of the convenience of impedance measurements over time. I just stand on the scale for a few seconds every morning, and I have stats synced that give me a good enough idea of my status (bonus for the added understanding of my hydration which calipers won't do). There's no cost or subscription for my scale aside from initial purchase (Withings aka Nokia Body Cardio), and it is regularly available for as low as $99 on sale. So after a couple years and hundreds of measurements the cost is negligible given the benefit. If I had someone regularly accessible to do caliper measurements, I would have it done to compare regularly but still continue with impedance because it's so convenient to do and track.
- parliament32 6y ago
  It's still useless if the data is garbage, which it really is. I had DXA scans done every half year for the last few years, and I've owned a few smart scales in that time (first Fitbit, then Garmin). DXA has shown me consistently dropping bf% (17.8%, 15.0%, 13.1%, 11.2%) while the scales (taking monthly averages) are all over the place (10.1%, 11.1%, 11.6%, 10.0% for the same months the scans were taken in). Impedance can show you a ballpark (and we're talking a wide, 10%ish ballpark) of where you are, but honestly you're probably better off just looking in the mirror and comparing to images online. I only mentioned calipers because they'd at least show you trends, which is where impedance seems to fail. Impedance is simply a poor way to measure bf%. Hydration might be a different story though. I'd recommend you do yourself a favor and just spend the $100 annually to see where you're at.
  - calvano915 6y ago
    I've had better experience with the Body Cardio scale. Though I haven't validated against other measures, I believe the body fat percentage is accurate enough based on my subjective opinion (it has not been generous to me like another poster's experience). Research has determined that impedance can be +/- 4% from actual in optimal conditions and my scale seems to fall close enough within that range. Regardless, I use it for all the variables tracked. I look at body fat percentage but body weight is ultimately the value of concern. I don't agree $99 a year is a good value just for bf%, because I do agree that visual impression means more than a specific number. The subscription cost for Amazon's service may be a great value (privacy concerns aside) if their photo algorithm is within a couple points of DXA or hydrostatic.
    - parliament32 6y ago
      >The subscription cost for Amazon's service may be a great value if their photo algorithm is within a couple points of DXA If it's accurate enough, I definitely agree. I'm looking forward to testing it out once it's available; since I'm one of those data nerds with actual ongoing DXA results, I'll be able to compare the two accurately. Although, pessimistically, I think if they had proven results within a few points they'd be a lot more quantitative in their marketing rather than the ambiguous language in the posts referenced above.