https://www.inverse.com/mind-body/fasting-gut-health-science
Also, Moon is relevant in Islam, as a calendar and timekeeping, nothing to be worshipped.
Also, All Monotheistic Religions have had fasting (the 3 big ones that survived so far) but again, the worst enemy of the people is their own selves and not the devil, and thus they modified what was given to them.
We know for a fact that this is false. For example, the Egyptians were building the pyramids and worshipping their gods at least a thousand year before any known monotheistic religion. The native people of Australia have even older polytheistic religions.
What evidence there is specifically in this case suggests that the monotheistic middle eastern religions were derived from the evolution of a polytheistic belief system into a monotheistic one via a stopping-off point that acknowledged multiple deities, but consistently only worshipped one of them. https://en.wikipedia.org/wiki/Israelites and https://en.wikipedia.org/wiki/Yahweh are worth a read, and there are several references to multiple gods in the Old Testament, often in the PAY NO ATTENTION TO THE OTHER GODS BEHIND THE CURTAIN sense rather than as direct callouts, as you'd expect.
So unless we might mean that the sidetracking happened before the archaeological record of Canaanite polytheism starts, it's not really tenable as a suggestion.
I do not say this to devalue or challenge anyone's beliefs today; just that ignoring facts has a tendency not to go well. The moral and personal value of religious belief need not, to my mind, lean on historical record for its validity.
"In Zoroastrianism or Mazdaism, however, fasting has been implicitly rejected throughout the faith’s history. Zoroastrian doctrine perceives no disjunction between spirit and matter along lines of good and evil; rather, it regards both as essential for achieving piety and both as susceptible to unrighteousness. Hence, Zoroastrians believe that the body should function as a means by which the soul can fight evil and regard any action that physically weakens the body as sinful. Moreover, sex is viewed as essential for procreation which brings more believers into the world. Standard or Young Avestan texts such as the Vidēvdād (Avesta, ed. Geldner, 3.33, 4.48, 7.70) emphasized that eating was essential for life, claimed consumption of meat enhanced spiritual perception, and suggested hunger and thirst caused much suffering. Pahlavi commentaries continued this anti-ascetic theme, stressing the notion of moderation or paymān between gluttony and privation in partaking of food, drink, and sex. Piety was said to result from not fretting about moderate consumption, and deviation from this mean was equated with concupiscence (Dēnkard, ed. Madan, pp. 267, 295)." https://www.iranicaonline.org/articles/fasting
Then Mani came along, introduced fasting. It was the main rival to Christianity before Islam came along. Both Islam and Christianity are heavily influenced by Mani and vice versa. https://en.wikipedia.org/wiki/Manichaeism
After 30 years of trying, I'm pretty sure I can't believe any religion was ever true. It's literally all made up, and the only bits that survive are the unfalsifiable parts or rely on nostalgia or ignorance.