When I was in college I took a couple of classes on Nutrition and Behavior, and it was fascinating how food effects our behavior. One of the assignments in the class was to write down everything you ate or drink for a week, see what was on that list the most, and then go without it for a week. The assignment was about experiencing withdrawal and we had to write a paper about it.
At that time for me what showed up most on my list was chocolate, and I went without chocolate for a week. I went through chocolate withdrawal, craving, and dreaming about chocolate at night, etc. For other students it may have been peanuts, or some other food that they frequented. There are all sorts of food addictions.
After graduating I had a client while living in Colorado, and Eskimo girl who went through withdrawal from whale meat. It was highly improbable to be a vegetarian or vegan where she was from in Northern Alaska. Up there they ate for much more then just nutrition. A lot of people can’t fast, or don’t fast, because of withdrawal discomforts. But I think short term fasting can be beneficial.
Back in the 1970’s hanging around with a bunch of hippies, the prevailing wisdom at that time was that we should chew our liquids and drink our solids. Chewing liquids meant swishing liquids around in your mouth and actually chewing it, and drinking your solids meant not to swallow your solids until they were semi-liquefied. This was suppose to better help digestion.
The thing is I am in my seventies and I know a lot of people in their eighties who are healthy, and they drink alcohol and do all the things some say they should not be doing. Talked to a lady who was 102-years old and she attributed her longevity to smoking cigars and drinking whiskey. I must say I feel better about staying away from those things, and I also feel very good about short term periodic fasting.