Fitness trackers can backfire when it comes to weight loss

That fitness tracker you got for Christmas promises to make you healthier — but it doesn’t promise weight loss. And now it looks like there’s a good reason why: people in a weight-loss study who used fitness trackers dropped about five pounds less than those who didn’t, according to a study published this week in JAMA.

For the study, 471 overweight people ages 18 to 35 were randomly assigned to one of two groups. Both groups received diet advice, instructions to exercise, and group counseling sessions. After six months, one group started using Fit Core by BodyMedia (which has since been discontinued) to use and the other didn’t. Everyone ended up thinner and healthier than before, though most people gained some weight back. But at the...