The Tanita, made famous by
The Biggest Loser, and other
body fat scales use bioelectrical impedance (BIA) to gauge the amount of lean mass, water, and fat in your body by sending a current from the metal plates under your feet through your body and timing how long it takes. While they are a relatively cheap option—you can find them for as little as $19.99 at any department store, and you can use them in the privacy of your own home—they are notoriously unreliable. Take a huge drink of water and watch your percentage change by up to 10 percent.
