Recommended reading:
https://dx.doi.org/10.1126/science.aau2095
Thank you. I know this publication, I have even blogged about it 
It’s now 4 years in a row that I do a short fast or a fast mimicking diet at the end of my season. Nothing crazy 2-3 days of fast or 5 days FMD in 2018
But I am not sure of the relatioship between fast and fat max/endurance, what do you mean ?