I use such a scale myself to see trends and have written about it.
viewtopic.php?f=1&t=57312#p576470As a numbers guy, I own a body fat scale. I know it is not accurate but I also know it is consistent and reliable. So, I don't believe the number I see is accurate, but I know if there is any long term trend up or down, that is most likely is accurate. For me, it is more fun then anything else.
However, it is important to know that any small changes (ie, +/-3%) are really meaningless because there are so many other factors that influence those numbers at those small levels including error rates. The gold standard is called a DEXA and I have had a DEXA done every day for a week including several times in the day without changing my routine in anyway and the numbers were inconsistent with great variability.
From the link above..
At Pritikin, we owned a state of the art DEXA, the new gold standard. For fun, I ran several test on myself within minutes of each other, and several test within a week, with out changing exercise or food and there was quite a variance, even outside of the +/- 3% accuracy you often hear.
I have a whole thread why I recommend weighing regularly on a regular scale and explain why there may be changes in weight that have nothing to do with losing or gaining muscle or fat. We don’t need an inaccurate scale for that. Most minor changes in muscle mass, if accurate, are actually due to variations in glycogen and water and most minor changes in weight are due to fluid changes.
viewtopic.php?f=22&t=57741While some individuals, especially those who like numbers, may choose to focus on these things, we do not recommend them, especially to the newcomer and especially to somebody posting for their first time. It is just not the focus of our program.
The single most important concept to someone trying to lose weight and or maintain it, is calorie density.
In Health
Jeff