Ramadan involves a number of societal changes beyond just not eating during daylight hours, from fasting to abstinence to busier public squares and restaurants. I'd want to see something control for the differences in movement patterns, passenger miles driven, meals eaten outside the home vs. at home, and so on. Public squares and restaurants are typically packed during Ramadan at night.

Here's one (theoretically) similar example:

https://www.datagraver.com/case/relation-terrorism-attacks-a...

Fasting during Ramadan is not the same as IF at all. During Ramadan you can't have even a sip of water, whereas in IF you are encouraged to drink water and even add a bit of salt if needed. That alone makes them too different to compare effects.

That’s a very good point and not something I had considered. Still, I am curious as to how the feeling of sharpness translates to actual performance.

The most obvious culprit is the lack of sleep, since feeding can only be done at night.