Have you been relying on your fitness tracker to measure your calories burnt? According to a study conducted by the Aberystwyth University in Wales, fitness trackers overestimate calories burnt by as much as 50 percent. The overestimation was found to be different for different activities, like walking and running. Various brands of fitness trackers were studied during the research. The study concludes that the information derived from these devices can be used as a motivational tool but not for altering your food intake.