Many endurance sports nutritionists claim that runners should spare their limited store of carbohydrate by trying to rely on fat for as long as possible, and possibly by becoming “fat adapted.” However, marathon runners can actually run faster by relying on carbohydrate for as long as possible in the race.
As was first discovered more than 100 years ago, scientists August Krogh and Johannes Lindhard in 1920 found that the amount of energy derived from the metabolic consumption of oxygen depends on whether fat or carbohydrate is the primary source of carbon fuel. More energy is released for a given volume of oxygen when a greater percentage of energy used during the activity comes from carbohydrate than from fat.
What does this mean, Dr. Jason?
I’m glad you asked.
Relying more on carbohydrate when you run improves metabolic efficiency and running economy because it enables you to run at a faster speed for the same amount of oxygen used or, to put it another way, reduces the oxygen cost of running at a given speed. It’s cheaper to burn carbs.
Focus on creating as large of a muscle glycogen fuel tank as possible through training and dietary manipulations, rather than trying to become a better fat burner. You’ll run faster if you’re a better carbohydrate burner.