The reason sled dogs are used in research surrounding fat/carbs is due to the endurance aspect. It has nothing to do with how cold it is. It's related to the conditioning of the dog for the event. The entire issue about carbs/fats is that the dog should be changed at least 4-6 weeks to a higher fat diet so the dog's body grows accustomed to the higher fat content. Lower carbs/higher fat improves the conditioning of the dog. The conditioning allows the dog to do what? Go at a faster pace, for longer, if properly conditioned. Carb loading is great for people. Carb loading simply isn't optimal for dogs as it simply isn't their primary energy source, and that will never change.