S2 Body Fat not accurate

• BUMP
• Consent to be added to an internal case - yes, I consent
• Consent to access your Garmin Connect account (if needed) -  yes, I consent
• What device/test are you comparing your Index readings to - [DEXA] GE Lunar Prodigy Primo, InBody 570, EVOLT 360, Garmin Index 
• What does your Index S2 display vs what does your reference device display -  S2 Fat = ~16-18 (note high variance), DEXA = 9.3%, InBody ~6%, and EVOLT ~16% 
• What is your activity class set to, and is this appropriate for your activity level - 10, Yes

Edit + scale info:

• Software is up to date — Version 2.08
• Synced Friday, Apr 1 at 06:00

The body fat measurement on this scale has been driving me nuts that past few weeks. I get dramatically different readings each day and it seems to be completely based upon what the scale reads for water %. If water % is high on one day, my body fat is low. If my water % is low, my body fat is high. It swings 1 1/2% from 1 day to the next and I measure at the exact same time (when I first wake up) every single day. This is really frustrating as I can't use to determine if a cut or bulk is working or not. It's really throwing me off. 

I have read that people have changed their age to be 18 years old to get it to work. Does that really work to give an accurate body fat percentage?  

All BIA-based platforms are extremely sensitive to hydration, some go high, others are calibrated to read low. Regardless, being [over|under]-hydrated can have a significant variance and other body type/build variables factor into the measurement. From my own measurements and those shared here on the Garmin forums the S2 is nowhere near a reliable reference for bulking or cutting at this time. My advice is to go get a DEXA/DXA, use that as a reference, then adjust the S2 curve. Also keep in mind that most people should be somewhat dehydrated when they wake, regardless of fluids consumed prior to going to sleep, regulating fluid intake prior to bed and when waking on a regular basis may help compensate for the disappointingly inaccurate readings the S2 provides.

I am not an RD/RDN, but I've found for most folks that I work with that 16-20oz of water just before bed and immediately when waking usually gets them close. That varies, point being you don't want the amount of water you take in to disrupt your sleep pattern (no getting up in the middle of the night to go...). Find what works for you and try to be consistent with that. If you do that you'll have one less variable to adjust for when interpreting the S2 readings. Also note that as one normally picks up 3 to 4 grams of water per 1 gram of glycogen. If you are high-carb and store one (1) pound of glycogen you'll also be picking up three (3) or more pounds of water along with that one (1) pound gain in glycogen. The scale can reflect this in unexpected ways. This is normal observed in individuals with high-carb macros. The hardest part for me is finding the right amount of fluid intake and which carbs I like - and digest - the best, then determining when to consume them.

That said, I am also high carb low-fat, at least during race season, which is 80% of the year for me. It may take a month or two for your body to fully adjust to those macros. Most BIA scales - the S2, and the InBody or EVOLTs you'll find at your local fitness centers will have similar 'hydration biases', and also count 'carbs' differently, where some consider excess in your system to be fat and other scales will lean towards that being muscle. Ideally, get the DEXA/DXA for a baseline. At a minimum I would find one of those others [InBody, EVOLT360, etc.] to get a second BIA-based opinion, weigh yourself on the S2 before and after the other 'opinion', and do that every couple/few months, or as needed to support other training goals or per advice from your primary care physician. Maybe do the DEXA/DXA once a year...

I don't want to hijack the thread so if you have any other questions on the topic feel free to DM me =]

I have just returned mine…@Garmin, please don’t make us loose trust in you 

Interesting that Garmin have locked the thread 'Body Fat % on Index S2 Smart Scale Seems Inaccurate' which had 286 replies and 19412 views!  Maybe they are hoping it will just drop down the forum list and eventually dissappear. 

Dispite many of us agreeing to share data with them they seem incapable of fixing the issue and so we either have to accept the product does not do what the Garmin marketing sales spin says or return the device and buy an alternative that does.

Garmin-Kevin you responded to the original thread, can you (or anyone else in Garmin) comment?

It might be due to having multiple threads open for the same issue. Garmin could merge topics when appropriate, I'm fine with that as long as they clarify the merge/justification in the thread. They know this issue is not going away and many of Us, myself included, view the S2 as a downgrade from the original Index - equal to at best if not 'less than'.

• Consent to be added to an internal case - yes, I consent
• Consent to access your Garmin Connect account (if needed) -  yes, I consent
• What device/test are you comparing your Index readings to - In body
• What does your Index S2 display vs what does your reference device display -  S2 Fat = 29.4 In Body = 19.2
• What is your activity class set to, and is this appropriate for your activity level - 7- Yes

It makes no sense! Activity level should be picked up from my watch and the muscle mass (S2 = 22.7kg In body = 30.5kg) calculations and body fat are way off compared with in body done less than an hour apart. Surely it's something with the algorithm? Anyone been able to find a work around? 

This scale is absolute garbage, just got one today took one BF measurement and it's going straight back.  My BF tested with calipers and another scale is 10% the S2 shows 26%.

This is a clown product, I didn't bother reading reviews before buying because Garmin quality, well that was my mistake. The forums are full of people complaining about its innacuracy and I should have done my research.

Heading to withings who actually can make a decent scale.