Every 10 years or so, like the cycle of the high protein diet, someone decides that fat would be a better fuel source for working muscles. It sounds like a good idea, we have more stored fat than carbohydrates so maybe exercise performance would be improved by burning fat.
Except we don’t work like that.
The thinking behind these studies goes something like, muscles use fat and carbohydrates as fuel for exercise and we have more stored fat so maybe we could go further if we accessed stored fat to supply energy?
Disclaimer – when I read these studies I wonder if the researchers ever bonked during a workout? Bonking for the uninitiated is uncomfortable, unpleasant and happens when you run out of carbs for fuel. You won’t do it twice.
The research published in the Journal of Applied Physiology blocked half marathon runners ability to burn fat during a treadmill test. They ran at 95% of their personal best half marathon times until exhausted. Blocking fat use had no effect on their ability to use carbohydrate stores. Carbohydrates contributed up to 91% of total energy used and the researcher concluded that
Adding that runners should focus on increasing carbohydrate stores before and during events to enhance performance.
I would like to add that in 1995 Professor Edward Coyle, PhD wrote the following,
“Fat supplementation and special diets have limited ability to increase fat oxidation in people, especially during sport competitions. Therefore, fat from body stores and/or dietary supplementation cannot adequately replace muscle glycogen and blood glucose as fuels for intense exercise”
Somethings, like fat oxidation, aren’t going to change, but you can. If you want to go fast, fuel up with carbohydrates.
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