A lot of activity trackers can count steps, track sleep patterns, monitor heart rate from your wrist, and display calls and texts. The does all that, too, but it can also measure your body composition. Read: it can tell you how fat or skinny you are.
Right now, we rely on the Body Mass Index to determine our ideal weight based on height. But it鈥檚 a crude metric. If you鈥檙e super fit but, say, a serious downhill ski racer, your quads and glutes are likely to be large and heavy, and that might tip the scales into the 鈥渙verweight鈥 category, according to the .
That鈥檚 because BMI is based on averages, not individuals, says Jeff Kim, head of marketing for InBody. 鈥淚t鈥檚 just a curve.鈥 When you get to the edges of that curve鈥攕ay a super trim, tall skier鈥攖he calculations fall apart.
The Band, on the other hand, works via bioelectrical impedance, the same way InBody鈥檚 deluxe devices work (those are more sophisticated, but the principle is the same). In essence, when you want to measure fat-to-muscle ratio, you tab through a menu on the watch and it sends out a low-level electrical impulse through your wrist. You then close the electrical circuit sent from the device by putting a few fingers on the Band with your other hand. More fat slows down the circuit, while less allows it to pass through our body more quickly.
The tech sounds simple, and , but it’s not infallible. Your hydration levels will affect the tech’s accuracy,聽exercise physiologist William J. Evans, director of the Nutrition, Metabolism, and Exercise Laboratory at the University of Arkansas for Medical Sciences, . Sweating or drinking alcohol聽could affect results, he says. That said,聽other studies have shown that bioimpedance is a more accurate measure of body composition than the rough BMI chart, so it’s a good start.聽
Kim says there鈥檚 value in this data, especially since there鈥檚 strong evidence that you might stay thin as you age, but, especially if you鈥檙e an endurance athlete, you could be losing muscle mass. If you can test for that easily, then the theory goes that you could also correct against the loss by adding more weight-bearing exercises to your regime.
Perhaps what鈥檚 most compelling about the system is that it shows how these devices are becoming sharper than mere digital pedometers鈥攁nd slowly but surely spitting out information that enables a proactive response to get you fitter.
Available in March for $179