Counting calories burned is not as easy as 1-2-3

The L.A. Times reports:

Whether you're trudging on a treadmill, pedaling on an exercise bike or taking on Roger Federer in a Wii game of Grand Slam Tennis, the machine will probably give you a reading of how many calories are going up in sweat.

In fact, no matter what you're doing -- and that includes doing nothing -- you can find a gadget to compute how many calories you're working off.

But should you put a lot of weight on these figures?

"The short answer is no," says Dr. Chris Cooper, director of the UCLA exercise physiology research laboratory. "They're all estimates based on a number of assumptions."