A question about fat measuring scales

(karen) #1

I’m noticing there are a lot of fat measuring scales on Amazon for $40 or less. my question is, are they actually measuring MY fat, or are they taking the average fat composition for a person of my height, age, sex and activity level, and extrapolating pounds of fat from my total body weight. It seems a bit surprising that a scale that could actually measure bone, fat and so on would cost so little.

I guess my question for y’all with scales like this: does the ratio of, say, bone to water or water to fat fluctuate (indicating the scale is actually measuring something), or is it always the same (indicating it’s just using a formula)?

(Wendy) #2

Mine says it uses an algorithm. I’ve heard being dehydrated messes it up some.

(G. Andrew Duthie) #3

They aren’t measuring fat at all.

Most, if not all, of these scales measure impedance. That is, you stand barefoot on a set of electrodes, which run a tiny electrical current through you. The resistance measured is used to guesstimate your body fat % by using assumptions about differences in impedance between fat and lean body mass.

As already noted, hydration level, as well as other factors, can affect the readings.

Nothing wrong with using them as a (very) loose measure of the trends, but not accurate at all, so far as I’m aware.

I have such a scale, and it’s not unusual for me to see a day to day variance of as much as 2-3%, though most days it’s pretty stable.

If you want accuracy, better to use calipers, or get a Dexa scan.

(Jay AM) #4

If you have to enter your age, height, gender. You can assume that it is basing its information on averages while taking into account your weight.

Here’s a good write up on BIA scales.

(Chris W) #5

i use the the omron body fat game pad, its only accurate to + or - 3%, my health coach told me that is the preferred method for men and the scales are the preferred method for women. The ideal unit has both a feet sensor and hand sensors, at best they are only so accurate. They are decent feed back if you use them regularly, but if you only use them on occasion with out much logging they are going to be of less use. Things like showering, sweating, hydration, meals all effect them. The omron game pad will also vary if you raise or lower your hands so I have to stand in the same spot and aim at the wall to get constant results. Several people have had dexa scans and found there BF to be lower than the impedance measuring devices.