I got some weighing scales for xmas (thanks redcrx) which tell you percentage of body fat and water and was just wondering how it works it out just by you standing on it???
it'll have metal contact pads that send elctrical pulses through you and the amount of resistance indicates the amount of non lean mass. Then the figures are extrapolated from knowd figures obtained from cadaver analysis. If it's one of the ones that do not have hand sensors then the results are less accurate.