It's an option.
I've tried it. I perform better on an omnivore diet.
I'll be posting more information soon on the different energy systems that the body uses.
The quickest source of energy that the body can produce to make ATP comes from carbohydrates.
There's a larger yield but it is more time-consuming and many more steps involved for the body to break down fat to get the ATP.
I was really into fasting and I still do intermittent fasting occasionally but I'm trying to bulk so I've been breaking my fast upon awakening with a vegan protein powder and almond milk.
The system by which when breaks down fat for ATP or energy can be made more efficient by going deep into a fast or by consuming a ketogenic diet.
I do not prefer a ketogenic diet either.
I've spent half a year on the Paleo diet and had very minimal carbohydrate. The carbohydrates that I did consume were complex.
When I'm sprinting and lifting heavy I can tell the difference and how I feel and perform when I have carbs in my bloodstream or glycogen in my muscles versus being on a 24 to 36 hour fast during which my body is burning mostly fats for energy.
My educated opinion and personal practice is to have a balanced diet rich in protein.