...in the New Scientist. Unfortunately you have to sub to get the full gist, but the article was based upon research reported in the Proceedings of the National Academy of Sciences.
Apparently men who run at least 4 hours a week consume 54% more fuel at rest than those men who don't run. At rest, runners will be burning extra fuel as heat. And if I'm right to make this link, it seems that wasting energy like this also means you are likely to live longer.
Altogether it was quite enough to get me jumping out of a nice hot bath, and out into the freezing cold to go for a jog. Now I'm off to slob out and eat pizza.