Body Fat% is a way off PART2

I changed my age from 57, to 37. And my 

I changed my age from 57, to 37. And here are the changes in lbs: Weight: same. BMI: same. Body fat: 29.3 to 22.6. Skeletal Muscle mass: 68.9 to 73.3. Bone mass: 8.2 to 10.9. Body Water: 51.6 to 56.5.  I don't have another scale to compare with, but using caliper for years, always put me around 19 or 20% body fat. So I googled and found this thread. 29% is saying I am obese, but I have been working out, sometimes full time, sometimes sporadically, since 1993. I am in week 4 of the vshred program, and I am doubling up at the gym 6 days a week. And my body fat % is not changing. Stays between 28 and 30%. Even when weight is dropping. Is age really that big of a factor? Is age the way they calculate bone mass and water? Bought the S2 last week.

interesting, this adds to the picture we're getting.

despite Garmin-AmberD saying "The Index S2 uses more of the impedance data rather than relying more heavily on a BMI value. We believe that this creates a more accurate reading of body data compared to BMI charts. The body composition metrics provided by Index S2 compares to known gold standard methods (Dexa scan, Bod Pod, etc.) favorably on average."

it seems that the reality is the scales give a BF reading primarily based on:

1. weight - obvious relevance
2. height - relevance to both BMI and impedance readings
3. age - somewhat relevant given that muscle mass tends to decline as we age but this is not always true and one of the uses of body analysis scales is to determine whether this is happening rather than just assume that it is 
4. activity class - this is where garmin seem to have completely failed to recognise that the garmin user group is typically more active than the general population so the activity class max of 10 is woefully inadequate to reflect the leanness of many users (without getting close to pro athletes)  

i should also highlight the phrase "on average" - ie for lots of people it will give excessively high numbers but for lots of other people it will give excessively low numbers so we're going to call that a good average, despite being massively wrong for many people. most of all though, on average the readings will be correct because it seems all these scales do is to report statistical average numbers based on the above knowns. so the only thing they really measure is weight, just like scales a tiny fraction of the price

Amber, I have the same problem. Brand new scale. I normally measure 4-7% body fat and am a locally competitive athlete, 2:31 current marathon time, and my scale shows my body fat at 18-20%! What should I do to get accurate readings?

you are unlikely to get any assistance from garmin on this i'm afraid - they seem to be in complete denial that there is an issue.

as per my post above, there are a number of settings that influence BF numbers on these scales. activity class is the thing you can genuinely use to indicate to the scales that you are not average. unfortunately it doesn't go far enough - i have updated mine to the max of 10 and still get BF double reality. beyond that, you can manipulate the other settings to get a correct BF number but with potential other issues resulting. if only garmin would place more emphasis on activity level and recognise just how much people vary from average, generally based on their activity level, they could at least pacify most of us. this should be a trivial software update.

in the end, the truth is that these scales will never produce meaningful BF readings as they just don't work. you can trick them into giving you any number you want but if its not a real measurement that will change meaningfully as your body does then what's the point?

What's the point of an expensive scale if these numbers are so inaccurate....

As best i can figure, the main issue with these scales as compared to previous ones i've had is that they know and use my age as an input to the calculations. an instance of a little knowledge being a dangerous thing. as many have found, adjusting your age setting is an effective way of manipulating the results to something more plausible, at the risk of affecting other things.

inspired by https://forums.garmin.com/sports-fitness/healthandwellness/f/index-s2-smart-scale/260712/index-s2-body-fat-algorithm-age-test i have submitted a suggestion to garmin, if others do likewise it just might get implemented.  

The scales make too many assumptions based on population averages for body composition for anybody outside of the average. Given that garmin users are commonly serious sports people this is a major failing. Fortunately, you have a pre-existing solution for this. The assumptions about body composition are heavily based on age. Anyone using garmin fitness tracking devices (and lets face it, these scales are worthless to anyone not embedded in the garmin ecosystem since the only thing they do above cheap scales is sync data to garmin) has a calculated "fitness age". For myself at 44, my fitness age is 20. When you have data to give a more relevant "age" then you should use it in this calculation instead of the chronological age which is not really very meaningful except to consider everyone as being the same which goes against the whole concept of body composition.

This should be the most trivial of changes to implement and I can’t see any downside. Assuming you trust your fitness age calculations it can only improve results. Anyone without a calculated fitness age can default to birthdate calculated age.

i submitted this through the support ticket i have open and also used https://www.garmin.com/en-US/forms/ideas/

Dear All,

after 3 months of measurement, today i went to make a fat measurement from a nutrition doctor, and that what garmin says is 21 % in reality is 14%. That's very sad considering that i've buyed this item specifically for the fat % measurement. As i can see, i'm not the only one with this problem. Can you please advice how to contact the customer service? Did anyone succed in sending it back and having some sort of refund? I think i'm going to write some bad review about this product, is really unacceptable that a company like garmin do such a big fail on a topic like this. 

I contacted customer service via online chat on Garmin Support page. They were very quick to agree that there was an issue and offered to replace the scale. The replacement scale works exactly the same with regards to the BF% measurement, which isn't surprising considering everyone else has the same issue.

In my case I also have BF measured in 20-22% range, and in reality it is probably closer to 14-16%, although I don't know for sure.