In terms of your comment regarding water yes millions of people may do this and as you say it has little impact and harm. I however prefer to drink water on a regular basis; it is what the body is primarily made up of and what the cells need for repair and regeneration. That and because many of us often think we are hungry when in fact we are dehydrated and the body is wanting more water – wanting more fluids this is why I encourage people to drink more water during fasting days than do a total fast.
And there’s more than anecdotal experience like Corbin’s that fasting can help people lose weight. In a one-year study, 100 obese adults ages 18 to 64 were assigned to three groups. One group practiced alternate-day fasting, eating 75 percent fewer calories every other day; another group followed CR, with a 25 percent calorie restriction every day; the rest were in a control group. Compared with the control group, the fasters averaged 6 percent weight loss, and those assigned to CR averaged about 5 percent, according to the 2017 paper in JAMA Internal Medicine.
Fasting during religious festivals is also very common. Common examples are Maha Shivaratri (Most people conduct a strict fast on Maha Shivratri, not even consuming a drop of water ), or the nine days of Navratri (which occurs twice a year in the months of April and October/November during Vijayadashami just before Diwali, as per the Hindu calendar). Karwa Chauth is a form of fasting practised in some parts of India where married women undertake a fast for the well-being, prosperity, and longevity of their husbands. The fast is broken after the wife views the moon through a sieve. In the fifth month (Shravan Maas) of the Hindu calendar, many celebrate Shraavana. During this time some will fast on the day of the week that is reserved for worship of their chosen god(s), while others will fast during the entire month.
Fasting is the willing abstinence or reduction from some or all food, drink, or both, for a period of time. An absolute fast or dry fasting is normally defined as abstinence from all food and liquid for a defined period. Water fasting refers to abstinence from all food and drink except water, but black coffee and tea may be consumed. Other fasts may be partially restrictive, limiting only particular foods or substances, or be intermittent.