But at some point you'd have to be literally burning fat away right ? That's the point of exercising after all. I'm just wondering about the timeframe of that loss, whether it happens as you're exercising or at some point afterwards.
iirc, the liver is responsible for breaking down fat. You don't burn it off in the sense of a car engine burning gasoline (can you say inefficient use of fuel?) but in the sense that chemical reactions happen. When fat is 'burned' for energy, I suspect that the waste from the chemical reactions will have to be pooped out before you notice a loss in weight.
This is all based on a very basic knowledge of biology and physics, btw. I know that in order to notice a significant weight loss, you'd have to radiate a LOT of energy (as xenu pointed out, E=mc^2). The weight of energy--in this case infrared light, which we usually think of as heat, iirc--is reallyreallyreallyreallyreally infinitesimal.