Tone is a small, Seattle-mad device that can measure how much fat that your body is burning. The device does this by detecting the level of acetone in your breath which is a byproduct of your body turning fat into energy.
Determining whether that three-mile run or the 8-minute abs session helped trim more pounds is difficult to measure for most diet-conscious people, who often must rely on a scale to determine exact weight loss. Even then, it’s hard to know if those lost pounds are water, fat, muscle or something else.