The Iditarod Calorie Burn

Iditarod dogs are mostly fueled by beef, corn-based kibble, chicken fat, beef fat, salmon, and hot water.

The Iditarod Trail Sled Dog Race starts today, and will wind up about 10 days from now.

This is the longest race on earth -- over 1,000 miles through some very tough country.

How do the dogs do it?

Magic!

Every sled dog in the Iditarod consumes roughly 12,000 calories a day, which is the equivalent of 24 McDonald’s Big Macs. Yet the dogs only weigh 40-60 pounds. How can they pack away -- and burn -- so many calories?

One secret is the food, which is loaded with fat. Iditarod sled dogs run on a mixture of hi-calorie corn-based kibble (such as Purina HiPro or RedPaw), beef, chicken fat, beef fat, salmon, and vitamin supplements. The whole mess is cooked up with hot water into a thick warm porridge which guarantees the dogs will get properly hydrated -- always a concern in the bitter cold.

Humans simply cannot consume -- or burn -- this much fat. The stomachs of top-rated athletes struggle to put away 6,000 calories a day, even though they typically weight three or four times as much. A top-end marathoner will burn about 100 calories per pound per day, but a sled dog can knock down 240 calories per pound a day -- and do it day after day after day.

Of course, being able to burn fat straight out of the blood stream is only part of what makes a long-distance sled dog a super athlete. Along with an astounding metabolic furnace, a sled dog has to have powerful lungs and a massive heart to power the circulatory system that is delivering oxygen and energy to the muscles. The aerobic capacity of a sled dog is about 5 times that of a human. And did we mention the fire called desire? Yes, that too is an essential element of a true sled dog!

The bottom line is that we don't fully understand what makes a sled dog tick. We do know that sled dogs can extract fat from their bloodstream and move it into the mitochondria of their muscle cells. We're just not certain of the mechanics. 

One thing appears to be true however -- the very act of long-distant running seems to trigger some sort of metabolic switch inside the dogs, and part of the switch has to do with insulin production. But the rest? We're not sure. 

Up in Alaska, some things are still a mystery,