See below an article with 'scientific' proof of why fasting is good for the body. I usually don't forward 'scientific' proof kind of articles when it comes to food, because I don't believe in so-called science when it comes to food related matters. The only reason I forward a 'science' backed article is to discredit other 'science' backed articles, which does not necessarily make this particular article true :-).
The entire establishment is culpable in keeping the population unhealthy, and that includes the food industry, the pharma industry, regulators, 'nutritionists' (one of the fields where the more they learn the more you pity their state of knowledge, since they learn more and more of the wrong things!), and a lot of well intentioned people who don't know better.
So what are the information sources when it comes to things like this? Try Ayurveda, yoga, naturopathy, Chinese Taoist rules, and the prescriptions of various religions on things like fasting (which has nothing to do with whether you believe in God or not).
So what are the rules when it comes to fasting and related matters? This is my list, based on my reading, from the above sources. I will any day stake my life on these sources rather than the modern food and pharma industry. BTW, I have been following most of these rules myself, and they seem to be working fine as far as I am concerned.
The rules? A top of mind list follows:
1) Eat only when hungry. What is the definition of hungry? The previous meal should have been digested, i.e. moved out of the stomach into the small intestine.
2) That brings us to the next question: how long does it take for food to digest? A rough guide (indicative only) is, say: fruits, which are the foods most attuned to the human body, take about half an hour to forty minutes to digest. A 'normal' well balanced traditional Indian meal (if you have not over-stuffed yourself) should take perhaps four to six hours. 'Tiffin' especially of the South Indian variety, perhaps two to four hours. Burgers loaded with cheese, etc. will take more than ten hours to digest.
3) What happens if you eat before the previous meal has exited the stomach? Let us say, you eat fruits immediately after a meal. The fruit gets digested fast, but has no way to exit the stomach, since the meal that is still getting digested is blocking it. Not having an exit route, it putrefies and ends up poisoning the entire system. So fruits should be eaten about an hour or more before meals, never after.
4) How much should you eat? Enough to fill half your stomach. Of the other half, one-fourth should be filled with water, and the other one-fourth with air, i.e. should be empty.
5) What about calories? Counting calories is a harmful thing to do; don't even bother with that nonsense.
6) What should be the main meal of the day? According to Ayurveda, the digestive fire is maximum at mid-day, so your main meal should be lunch. Breakfast, of course, can be had, but the most important rule is to keep your dinner light, very light. Eat very little in the evening, or not at all (if you can manage that), and eat it at least a couple of hours before you go to sleep. There should be no food in the stomach when you hit the bed.
There is an old saying that the person who eats once a day is a yogi, one who eats twice a day is a bhogi (fortunate person), and one who eats thrice a day is a rogi (a diseased person)!
This modern tendency of doctors advising people to eat every three or four hours is total rubbish. If it is justified on medical grounds, like say diabetes, I have nothing to say except that one should introspect on why one got a lifestyle disease like diabetes in the first place. It is sometimes also justified on the grounds that eating often keeps the metabolic rate high, thus preventing weight gain. That argument to me sounds worse than models justifying chain-smoking on the grounds that smoking kills the appetite thus enabling them to stay thin!
8) What about fasting? Fasting is good. It is good to fast once in a while. There are various ways to fast. You could start, for example, by undergoing a juice fast, where you have only liquids. Or you could just skip four meals in a row. Or whatever. When all you are required to do is not eat, how much theory do you need to support that? Come out of the fast gently, meaning don't visit pizza hut or McD's to break your fast - some juice or fruits or light khichdi as the first meal would make a lot of sense.
All religions advocate fasting, and for good reason. The body gets the chance to divert its energies to throwing out accumulated waste from the cells, and generally clean itself up. If you keep stuffing yourself, when will you give the body a chance to do that?
The link to the article I mentioned is attached below: