PS In my last post, I mentioned body fat an analysis scales. These are made by Tanita not Tanica. See www.tanita.com . Omron also make them. They use bioelectrical impedance analysis (BIA) technology. Like many devices, even if they're not 100% accurate, they are useful for monitoring your trend (ie are you gaining or losing body fat). I haven't read enough to get more technical than that.
Ben Balzer