I also question religious devotees adherence to their religion. There are no stats on it and it is impossible to measure... Perhaps a significant number of them secretly cheat.
In fact one of the recruiting rules was "2) Subjects who plan to fast during the religious month of Ramadan" and therefore "All subjects fasted for more than 14 h daily for 29 days beginning from May 06, 2019, until June 03, 2019".
See full text https://www.nature.com/articles/s41598-020-73767-w
1. Why ramadan is not explicitely told in the title. 2. Why using "dawn to sunset" which is not helpful at all to make generalisation (scientists usually have a clock). 3. Why the diet during the night is not explicited (at least in the abstract). 4. Why this would have different results if the diet is during the night or during the day.
All of this makes me suspicious that this is a kind of retro-science propaganda to make Ramadan looks healthy and justify the religion.
I maybe wrong but the abstract raises too many flags to not care about this hypothesis.
Or see https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3263199/ - "The recorded high prevalence of the MS and its key cardiovascular risk factors (15-60%) among Middle East population mandates the need for a national and international prevention programs to combat obesity, diabetes, hypertension, dyslipidemia, smoking and related comorbidities."
So I'm not sold.