There is lots of academic research on the subject.
Here is one example...
https://www.researchgate.net/publication/40759596_Effects_of_Ramadan_Intermittent_Fasting_on_Sports_Performance_and_Training_A_Review
That is nonsense. So if our best player was suspended and missed a league win vs a bottom of a table team you wouldn't then start him in a cup final a week later because it would be changing a winning team?
No we didn't. A newly promoted from L1 Saints finished 2nd and West Han were 3rd and went into the playoffs, despite the Hammers having a vastly more expensively assembled squad than us.