Body Fat% is a way off PART3

that sounds even more wrong than everything else from these scales.

the only chnage that should happen over the course of a run is some dehydration, yet you are seeing the opposite of that, plus some other changes. the dehydration will result in the weight loss you are seeing, the scales are then completely misinterpreting the body composition changes. it is reasonable that muscle mass is considered lower since this is closely linked to hydation, yet the scales are not identifying the hydration drop and the muscle mass drop is not real, only perceived due to the hydration drop. unfortunately you will not have lost any fat during a run (but might afterwards)

Hi I just moved from Withings to Garmin and found the Fat Percentage to be well off. Is there an athlete mode on them or something. I know I am overweight and have about 15% body fat (as per Withings and I can agree with that but 26.9% on GARMIN ?????) . However I am more muscular due to years of weight training and I don't think the Muscle percentage is correct either. As I said I have just purchased this S2 and so far am very disappointed.

I know 2 Options:

Set your Activity Level to 9 or 10 or change your birthday

I am going from a Withings to the Garmin scale and concur that the Body Fat measurement is way off.  I am literally a bone, super skinny with very little fat on my body.  The Garmin scale says my body fat is 25% which can't possibly be the case.  I bought the scale hoping for more accurate readings than my Withings.  Honestly, I don't trust the other measurements either.  Wow!  Not a good investment.  Apparently, they can't fix this with software or they already would have.  

No that didn't work either. I set it to age 23 with a Activity Level of 10 and still I am 21.7% fat...... Weird thing is I have a visible six pack, 33" waist, 43" chest @ 186lbs and 5'8" tall. I work out between 3 and 7 times a week and monitor my food intake!!!! I do not eat junk and I am NOT lazy or couch potato. These scales DO NOT WORK for these measurements!!!!!! GARMIN - take some ownership and fix your algorithm !!!!

Try setting your birth year to 2005. For me, it gives me a similar value compared with the tanita scale

absolutely it shouldn't require workarounds. more importantly though, given it does require such a hack to get anything lke a correct result (and for me at least its still a bit off) you have to question whether it is of any use - if you change the inputs to get the output you expect then you're not really measuring anything. will it then actually change appropriately if your body composition changes?

Of course but that's why we are here waiting for a solution from Garmin(if there's any...)

Changing age is a really poor workaround and we shouldn't be forced to do that. Changing age would likely affect VO2max calculation, Calorie burn, and potentially more.