In: food.
Also: wet fasting.
Dry fasting
Fasting is a method of restricting food intake, and has been practiced for thousands of years.
Dry fasting means not eating and not drinking anything for X days.
It’s actually not extreme to have 1 day without food or water. If you eat you last food at 6 PM and you drink 1 cup of water around the same time, if you wake at 8, you already had 14 hours of dry fasting. If you drink coffee instead of water first thing in the morning, it’s not enough hidration anyway, so you can add a few more hours of dry fasting.
The body can survive a few days without any water, 1 day is absolutely not a problem. The mind will make it a problem, especially if you have other people eating in your house, or if you have food and drinks that you see and crave.
You won’t find many studies about dry fasting, not surprising at all, because who would pay for a study that doesn’t sell anything in the end? Fasting means reducing comsumption, the opposite of buying, it’s not like a wonder pill that people can buy, so it’s not profitable for the industry to study.
In Romania we call it “black fasting” and it used to be normal practice, 1 day before Easter, Christmas and other Christian holidays.
There’s several types of fastings: no animal products fasting, or no solid food at all, or no food and no water. Most people keep the first one and sometimes 1 day of water only, or 1 day of nothing.
Personal
My grandma was a religious person. She used to keep all the Cristian holiday fastings. Before Easter, she only drank water and she had some days without any water in between, for a few weeks. She was working on her farm all this time.
I didn’t try any dry fasting until I was an adult. I don’t find them very useful personally. I prefer wet fasting.