Led by a video projected on to a whiteboard nine children, a mix of Latinos and African-Americans, walk or jump on the spot, swing their arms, stretch and reach in an exercise class that lasts around 15 minutes.

BBC: Obesity rates fall in Philadelphia

"The big picture here is, this is certainly not adding up to hundreds of calories a day by any stretch, " says Mendel, the programme director for exercise science at Mount Union University in Alliance, Ohio.

BBC: Who, Why, What: Can foods have negative calories?

It's still a bit of a stretch, which means your hands will thank you for the extra exercise, but Samsung also manages to alleviate the concern a bit by introducing features that recognize you're not going to be able to use both of your palms at the same time.

ENGADGET: Samsung Galaxy Note II for T-Mobile review Mobile