But just how much fitness trackers contribute — if at all — to better health and lower health care spending isn’t yet known. Among the studies that cast doubt on their effectiveness is one published in 2016 by the University of Pittsburgh. That research found young adults who used fitness trackers in the study lost less weight than those in a control group who self-reported their exercise and diet.

Source: Advocates Worry About Fitness Tracker Data Privacy : Shots – Health News : NPR