Body fat monitors?

I'm now starting see body fat scales that claim an precision of 0.1% rather than the 1% that earlier ones claimed. If this accuracy is genuine it looks like a better way to measure the progress of my diet and exercise program than just weight alone. But of course, just because they print out a value to 0.1% doesn't mean that the measurement really is that accurate and 1% is a rather coarse increment.

Does anybody have any idea just how accurate these really are? If you measure your body fat several days in a row how much is the jitter? I know that skin and sweat have a large effect on electrical resistance, for example.

Thanks

Probably +- 5%, unless you're highly muscled, very overweight, have dry skin, or in some other way don't look like the people they used to develop their algorithm. In that case, it's +-20%. They absolutely are not accurate to a single percent, much less 0.1%. The day-to-day variation with hydration and so forth is easily 1%.

More than that. I had fluctuations from one day to the next of 3-4% on a regular basis. It's doubtful[1] I could gain or lose 5 pounds of muscle in a day. The rolling average was more consistent, but you would expect that.

-Richard Campbell. [1] Impossible.

Can you actually buy a body fat monitors ?

Yes. Tanita is the big dog with HealtheTek gaining. I am skeptical of the 0.1% accuracy.

I think the supposed claim 0.1% accuracy may be the result of a misreading of Tanita material. Their most accurate scales provide read outs up to .1% accuracy. That doesn't mean, and they don't equal, that the reading is within that limit of approximation to actual body composition. On its web site the company claims only accuracy within 5 percentage points.

The reason, I think, for providing scales with far greater accuracy are twofold: test-retest reliability is much higher than absulate accuracy; people can use the scales to check hydration levels, based on just those changes that detract from reliability.

To claim .1% accuracy would probabily constitute fraud.

Stephen Diamond

While it is true that accuracy of the Tanita scale isn't '0.1%' (that being nothing more than its granularity), the fact is that there is no reason to think that the scale regularly puts out numbers at the far end of its scale of accuracy! Even though it is accurate to +/- 5%, just like most measuring devices, most of the time it should be accurate within a much smaller range, typically around the middle of the range of accuracy. The quibbling about the accuracy of the Tanita is seriously over-blown, probably coming mostly from folks who have a personal preference for

What isn't clear to me is exactly what the range corresponds to statistically. The standard error of measurement, the range of accuracies in 90$ of instances, or what? Perhaps there is some convention as to the precise meaning of 'range' I am unaware of. In the nature of things, 'range' cannot mean the absolute range, capturing 100% of properly taken measurements.

Stephen Diamond

The point is that the likelihood that any one person's particular measurements being grievously inaccurate are incredibly small.

If that's the case, why doesn't Tanita state to what statistic plus or minus five corresponds. If, say, only 2% of those using the instrument properly are outside that range (and if we agree that the 5% range marks the boundaries of grievous error), you would think they would plainly state that precise fact, somewhere.

On the other hand, If Tanita vaguely alludes to a 'range,' the chances are that range is as narrow as Tanita can get away with

A friend of mine calipered out at ~7%. He picked up an electronic BF tester . . . it read 40%!

So much for the +/- 5%! Yikes.