Fitness trackers have opposite effect

Fitness trackers designed to help people keep in shape offer no useful weight-loss benefit, a US study suggests.

The two-year JAMA study of 471 overweight people found that the wearable devices may help people lose weight but they’d be better off if they opted for a conventional weight loss approach by exercising under their own steam.

Participants were placed on a low-calorie diet, prescribed increases in physical