Are fitness trackers, the increasingly popular devices championed by employers to help workers develop healthier lifestyles, as all-knowing as they are made out to be?

Researchers who recently compared the devices to traditional methods of counting calories say they are not impressed. The two old school methods had people consume a liquid that allows analysis of calorie expenditure via urine and, of course, shutting them in an airtight chamber and monitoring every calorie consumed and burned.

In two experiments, the 12 gadgets, including the Fitbit Flex and JawBone Up24, did not appear to accurately track the number of calories consumed and burned. In some cases they dramatically underestimated the number of calories burnt, and in other cases, they overestimated.