"A roughly 55-pound sled dog can burn up to 12,000 kilocalories per day - the equivalent of 24 Big Macs. A human athlete, to sustain Iditarod-level performance for just one day, would have to eat, *and* efficiently process, the equivalent of 72 Big Macs." (DogBlog.com)
Though the stats are pretty staggering, knowing that the Iditarod is a 10-20 day race where the dogs mush for 1,100+ miles (temps, can be as low as -40 degrees fahrenheit), I wouldn't say that the revelations here blew my mind. What is most impressive, however, is that these dogs can break down anything:
"Sled dogs eat a commercial race diet, but it can be supplemented by anything from salmon to congealed lard, all of which they’re able to convert to fuel."
Hence, the relevance of the Big Mac analogy above. I can't even jog after eating a turkey burger, by the way.
Short of going back in time and studying beasts that did battle in the gladiatorial arena, I think we might have found nature's preeminent competitor here.
Iditarod Dog Athletic Supremacy Explained (Discovery.com)