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Body Fat percentage wildly inaccurate, firmware algorithm update needed?

Xanomead
over 1 year ago

For a company that specializes in fitness and health related metrics, the Index S2 scale is an embarrassment. This morning my scales gave me a body fat percentage reading of 23.1%. This is me post work out a few hours later. Now I don't know what my actual body fat percentage is, but a look online at examples makes me fairly confident that I'm below 23.1% body fat, I'd even suspect more than 5% below, and it's said that impedance measurement can be plus or minus 5 percent. So the scales seem to be even less accurate than what would be considered the worst case scenario. Given the price of the scales, and that this is the kind of thing Garmin specialize in, it's an embarrassment. Will anything be done about it? And beyond keeping the surface of the scales clean, is there anything that can be done to try to improve the accuracy?

It seems to me that the algorithm is putting too much weight on BMI when trying to calculate body fat percentage, and that's making the measurements a complete waste of time and money.

  • 0 1 month ago in reply to NEILWT

    What strikes me most about those results is how BMI and body fat seem to be so close in value. I previously strongly suspected that the algorithm was weighted far too heavily by BMI, so even if you were very lean but with crazy muscle mass, it'd estimate your body fat as being higher than it really is.

    I wonder if there is an overlap in water and body fat and skeletal muscle though, as that might explain why the percentages add up to more than 100... But if not, then it looks like something is seriously wrong.

  • 0 1 month ago in reply to Xanomead

    The simple consumer in me, suggests, these are just a calculation based on hundreds of set examples.  There are no other inputs to inform the results, ie.  The alogirithum could include physical dimensions, such as ankle, wrist, thigh, waist etc….  I would have thought Garmin has access to this data, but for whatever reason has not chosen the complicated route.   Something, I would love to develope.  But that’s all behind the scenes.  The simple consumer in me wants to see, weight, bmi (no matter how false), then water content, fat, bone, muscle, organs etc…..  these are all hypothetical, as it’s just a number - but at least make them add up to 100 percent….  It would stop the challenges I’ve read.   A lack of definition and inaccurate representations always cause conflict.  Incidentally - WII Fit gave  a body shape representation -  I was always the chubby one base on weight and height - come on Garmin - figure it out!

  • 0 1 month ago in reply to NEILWT

    I am having the same problem.  For reference, I am a 48 yo woman, and believe I am somewhere closer to 25% body fat range based on past testing, images of women and body fat %, and numerous calculations including waist, hip, thigh, neck, wrist, and forearm measurements.

    I have tried the following:

    - Changed my activity level to 8.  NO DIFFERENCE.

    - Changed my age by -20 years.  Body fat % NO DIFFERENCE.  Muscle and bone mass went UP.

    - Removed my age.  NO DIFFERENCE (muscle mass and bone mass stayed at the younger setting, the last one used).

    - Entered a value (27%) in the user settings to "calibrate" the unit.  Body fat % went UP.

    The last 10 days (including today) are below (today is the last row).  You can see the jump in muscle mass and bone mass (bolded), while the other stats stay about the same.  That was when I made myself 20 years younger.  It doesn't make sense that my weight, body fat %, and hydration would be static (the changes there are very small) while I'd gain 6.6 lbs of muscle and bone mass at the same time.  It doesn't add up.  And you can see my calcs - when "old" the total weight was 117% of the given weight, and when "young" the error is higher at 121%. 

    I approached this by calculating the weight of the given percentages.  I believe you calculated the percentages of the given weights.  Same overall approach, different in the details, but similar in the results.  Either way, it's not adding up.     

    Weight

    BMI

    Body Fat %

    Muscle Mass

    Bone Mass

    Hydration

    Body Fat Calc

    Hydration Calc

    Total Wt

    Percent of Weight

    138.8

    23.1

    30.7%

    44.6

    5.1

    50.6%

    42.6

    70.2

    162.5

    117%

    137.5

    22.9

    30.2%

    44.3

    5.0

    51.0%

    41.5

    70.1

    161.0

    117%

    135.8

    22.6

    30.8%

    43.8

    4.9

    50.5%

    41.8

    68.6

    159.1

    117%

    136.2

    22.7

    30.6%

    48.3

    6.0

    50.6%

    41.7

    68.9

    164.9

    121%

    138.1

    23

    30.3%

    48.7

    6.1

    50.9%

    41.8

    70.3

    166.9

    121%

    138.6

    23.1

    30.2%

    48.9

    6.1

    50.9%

    41.9

    70.5

    167.4

    121%

    139.1

    23.2

    		 30.1%

    49.0

    6.2

    51.0%

    41.9

    70.9

    168.0

    121%

    136.1

    22.7

    30.8%

    48.3

    5.9

    50.5%

    41.9

    68.7

    164.8

    121%

    135.4

    22.6

    31%

    48.1

    5.9

    50.4%

    42.0

    68.2

    164.2

    121%

    135.6

    22.6

    30.8%

    48.1

    5.9

    50.5%

    41.8

    68.5

    164.2

    121%
  • 0 1 month ago in reply to Readsunlove

    Thanks for reviewing and sharing a different approach with similar results.  :-)

  • 0 1 month ago in reply to NEILWT

    Some might be interested in this….  Makes me feel better about myself, that I am average and ordinary, maybe slightly overweight, rather than fit…. But the calculation feels right.   Garmin need to take note! Or at least review and provide as option….

    www.calculator.net/body-fat-calculator.html

  • 0 1 month ago in reply to NEILWT

    I'm going to send this to Garmin support, at the very least I would like them to explain why total weight is able to exceed 100%

    I honestly doubt the the Index S2 is even taking a body composition reading using electrical impedance. The top panel seems to just be glass.

  • 0 27 days ago in reply to Xanomead

    Did you send this to Garmin and did you get a response?

    Since entering 27% my body fat % has continued to increase, now at 32%.  My weight has held around the same, 135-138, and I do both running and weight lifting, so I'm not losing muscle here.  There's no way I'm 32% body fat!

    I did switch my age back to my actual age and my muscle and bone mass both went down (as expected).

    I wish Garmin would do something about this.  The forum for the Index S2 is full of threads (YEARS of threads) with people complaining about the horribly inaccurate body composition, and it's clear that very little is actually measured, instead it is all calculated.  I think weight is the only thing measured, everything else based on age and gender, and maybe activity level (though I noticed no difference there).

  • 0 19 days ago in reply to Readsunlove

    Hi, sorry for the delay. No, Garmin just fobbed me off, said that I had to submit the report somewhere else, gave me a link to another page, but you need to select the product in order to submit and the Index S2 is specifically not listed.

    Perhaps Garmin are happy to sell this product knowing full well how bad it is, and don't want to get constant reports, so they removed it?

    I replied back saying that support could just do their job and send the report to the correct place, but they never replied.

  • 0 18 days ago

    not sure you can sum water and muscles as ~80% of muscles is water...

  • 0 18 days ago in reply to Tekniq

    I didn’t send to Garmin.  They wouldn’t be interested.  However, the water and muncle/water argument is not relevant.  A total is a total, all we’re asking is to display a body composition that is roughly appropriate, but does equal 100%.  If muscle is water, the define what’s included somewhere.  This is not a flame, just an explanation.