In March 2019 researchers from Saudi Arabia published the results of their study to assess whether intermittent daytime fasting increased sleepiness. Eight healthy individuals, average age 24 years, were included in the study. Slow frequency EEG waves reflect increased sleepiness and each individual underwent EEG assessment 1 week before Ramadan (non-fasting control), 4 weeks before Ramadan whilst fasting from dawn to sunset for 1 week, during the second week of Ramadan whilst fasting, and 2 weeks after Ramadan. Results showed that during waking hours no difference in EEG assessments was observed between the non-fasting control period and fasting during and outside Ramadan.
Almeneessier AS et al. Effects of Diurnal Intermittent Fasting on Daytime Sleepiness Reflected by EEG Absolute Power. J Neurophysiol 2019 Mar 4. [Epub ahead of print]