How accurate are the scales that measure body fat?

Question

I am speaking of the floor scales that anyone can purchase for little more than a simple bathroom scale. Apparently they generate an electronic current through your body that is then measured to calculate your body fat percentage. I understand how such a device is supposed to work but I wonder how it compares to a professional body fat percentage test. It just seems like a consumer product rather than a scientific instrument. Thoughts?

Answer 1

It depends totally on the brand and a lesser degree the model.

Unfortunately none follow a set template and are based on internal 'research' for their resistance calculations. I am the head of QA for a sporting goods manufacturer and recently trialled a common American brand which we were looking to rebrand under ourselves in a new design. As part of the QA process accuracy is a must when making fixed claims on peoples body fat, muscle etc for legal reasons. As a trial we bought 6 other off the shelf brands with similar function and claims then ran a trial of 10 people (5 men, 5 women) through the six current and our sample received.

Of these the variances were 10-15% on total body fat between some brands! The results were needless to say outright terrifying that some are out there telling people they are overweight when clearly they are not. Some brands were recording body fats of over 30% claiming 'obese' for some who are in fact amateur athletes. Needless to say our sample received failed and on questioning the discrepancies of the manufacturer (who sells under a license brand to the US and Europe) it was revealed their research and analysis was based solely on Chinese participants whose bone and body structure is quite different to western people. I personally found the most accurate of the 'averages' to be weight watchers or propert brands for this comparison.

I won't say the names of the others for legal reasons, in total 3 of the 7 seemed accurate with a <5% variance, the rest were very inaccurate. I would suggest having your body fat % measured professionally, then test this against anyone you know how has one or in-store units to see which you can find is closest. In short, some are 'reasonable' once used as a benchmark but be wary of thinking they are all the same, this is really not the case.

In my experience the best you can do is get a good set of scales for weight and stick to using a measuring tape for recording on paper between weigh ins to see what your different body measurements are like otherwise do as previously suggested but use the scales as an ongoing starting benchmark only (once have a set, only compare within that set) to see changes\effects of dieting but never rely on them as dead accurate overall, just to see how your tracking from the starting point.