As for many people, the New Year means a new life and a new them. Most would first and foremost want to shed those bellies off from the holidays. And the most "in" thing to help with the ultimate challenge is some wearable technology.

Although these wearables promise to keep track of physical activity and other behaviors, users are warned as they are inaccurately measuring sleep, according to a new research. The new study systematically reviewed 22 published studies that covered activity trackers', namely, Fitbit and Jawbone, potential to monitor steps, distance, physical activity, calories (energy consumption) and sleep.

A number of the articles claimed that both in the lab and field, both devices were able to carry out the counting task accurately. On the other hand, only one study scrutinized Fitbit's ability to measure distance, where it was found that the tracker is predisposed to overestimating slow speed and underestimating fast speed.

Physical activity was measured through its accelerometry. High correlation was noted in one study, and wide range correlation on the other. Furthermore, assessing a number of various comparative analyses found that both wearable devices underrated calorie levels while inflating sleep hours.

As a result, the new study pointed out that these devices show preciseness when measuring steps but may not be on calculating calories and sleep. In order to keep these tracking devices accurate as possible, lead author Kelly Evenson from the University of North Carolina Gillings School of Global Public Health and his colleagues highly suggested to wear the tracking devices in the same spot, constantly update personal details like weight and height, adjust the walking stride, input additional vital data in its journal and interact with the sleep mode feature.