S2 Scale does not use impendance to measure BF% instead a algorithm based on weight, age and sex alone!

Not going to hold my breath if they had a year to fix this already. Really struggle to understand how they get away with this, isn’t the whole purpose of this scale to give accurate BF% ? How can they just fake it with a simple algorithm and not have to recall thousands of units?? It’s really bizarre. I’m just going to return it right away, shame coz I figured it would link nicely with my Garmin watch.  Do you recommend any other scale? Thinking of replacing it with the Withings Body+ in the shop tomorrow. 

Mine seems to vary too much to be as simple as using this formula. If this were the case, then BF% would be relatively unchanged from day-to-day if my weight isn't fluctuating much, but indeed my BF% is fluctuating by quite a lot (anywhere from 19% to 24%) with my weight remaining relatively stable at 162-165 pounds.

Tried on 3 family members .. each time exactly as per the formula. It was all first weigh-ins so maybe it changes once you do more consecutive weigh ins? Still funny its just formula and nothing else for the first time.. puzzling. 

My impression is that BF% seems to vary based on how dehydrated I am. It interprets me being dehydrated as having more BF%.

But still, it is grossly inaccurate. For me BF% is around 20% +/- 0.5%. I think my actual BF% is around 16%. Using the formula above it would be ~22.5%.

The worst thing is that Garmin now uses BF% as an input into calculating Fitness Age. So that is inaccurate too.

Agreed... I'm very disqppointed in the way Garmin sold this.

My scale says I'm at 24% BF, which is quite ridiculous when a few years ago with less exercise and similar weight, I was at 15%. And changing the activity class doesn't even make a difference when it's a parameter that they have attached to the scale!

So ridiculous.

I wish I had done more research about this before buying one.  This is a year later, but 2 years since the release and from what I can see there has been no change in that entire time.  I will continue to use my 15 year old Tanita that has an "athlete" setting.  What I don't understand is that my Tanita uses bioelectrical impedance - it has metal pads that I have to stand on.  The Index S2 seems to be all glass? Isn't glass an insulator?  How is electrical even supposed to work on this scale?  It doesn't clearly. But also I agree with OP - I call BS on this claim.

Not necessarily. My withings was all glass and matched my Tanita. If this is in fact true - it’s a joke. It has to have impedimence or it wouldn’t be able to recognize hydration or bone mass no?

It is easy enough to test. Try stepping on the scale in rubber flip flops - it won't work.

Based on my observations, the electrical impedance is in fact taken into account. There are certainly cases when, everything else equal, the BF% varies from one day to another. But I think the contribution of the impedance into the result is rather small and other factors like age, weight, and height have a much greater impact.

For me, the BF% produced by Index 2 varies slightly between 20-22%, while in reality it should be 12-15%. One time I measured BF% with a professional grade scale that costs several thousand dollars, and it was 13%.

That sounds more correct on the impedance - my observation is same as yours - Im around 13% BF and the scale shows 18%. Its always a constant 5% for me. I wish in the mean time they would have an 11 setting which allows you to put a factor in there so for me it would be .72 (13/18) and I can have readings that match my history in TrainingPeaks until they fix this. Im completely baffled by Garmin's lack of response here.