Fasting is common among all traditions and is an ancient practice.
It is also researched in modern universities.
Perhaps, the clearest and most comprehensive documentation is found among Muslims.
The Arabic word for fasting is sawm – صوم –
It is obligatory for Muslims to fast one month a year.
This month is called Ramadan – رمضان –
The fasting starts at dawn and ends at sunset each day.
People who have health issues are exempt from fasting.
This is also the rule if it threatens their health for whatever reason.
This health issues could be permanent or temporary.
For example, a woman who is breast feeding may not be feeling strong enough to fast.
Therefore, she is exempt. Furthermore, she is rewarded for not fasting in this case.
Fasting is mainly a ‘no outward action’ way.
Hence during the fast, you are not allowed to eat, drink or have any lawful sexual intercourse.
As the outward actions are minimised, the inner ones are maximised.
Hence the main activity happens in your ‘inner world’.
That main action is to sharpen your resolve not to harm.
However, if that is not possible then you move to the next level and that is to reduce harm.
This harm could be personal, family related, communal, environmental, local or global.
Hence someone who truly fasts will naturally support the following causes:

• no to harming oneself or others
• no to environmental harm
• no to the use of religion (or anti-religion) to support corruption in an administration

In the Quran, this is all summarised in one word : -تتقون-

“
يَا أَيُّهَا الَّذِينَ آمَنُوا كُتِبَ عَلَيْكُمُ الصِّيَامُ كَمَا كُتِبَ عَلَى الَّذِينَ مِن قَبْلِكُمْ لَعَلَّكُمْ تَتَّقُونَ”
البقرة

“O you who have believed, decreed upon you is fasting as it was decreed upon those before you that you may become rooted in ‘not harming’ ” (1)
Quran 2:183

When fasting, you will find that your senses are sharper.
All of a sudden, you will find that you can clearly hear and see.
Even the sense of smell is sharpened.
The mind is also sharper.
There is no better activity than contemplating the meanings of the Quran and helping the needy.
When you feel tired, rest.
From ancient times, humans used the sun and the moon to manage their daily life.
This is clearly found in the Sumerian writings and it is from them that we inherited the 60 minutes in an hour, the 360 degrees of a circle etc.
The moon sighting with the naked eye is the simplest in marking the beginning and the end of each month.
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(1) This is usually translated as ‘become righteous’. Unfortunately, you will also hear some preachers translate it as to ‘fear God’. I find that those translations miss the point and are diversions from its rooted meaning.