You are a soul, composed of three parts: body, mind, and spirit. You are so much more than your body, and there are certain aspects of your body that you need to be the master of, not the other way around. Hunger is one aspect of your body that you need to master. Don't try to control your appetite, but don't let your appetite control you. Fasting is one way to master it.
Fasting is a spiritual discipline, not a health related activity. I do not suggest that you go on a fast to lose weight. That is counter productive. Fasting causes your body to shut down or slow down certain systems, since it has no idea when the next meal is coming.
Take the time you would spend eating and use it for a spiritual activity. Obviously, I would suggest bible reading and prayer, but you may be into meditation or yoga or whatever, and I understand that. The point is that fasting isn't just about not eating.
On a spiritual level, fasting is an offensive maneuver. There are defensive spiritual disciplines, but when you want to attack a problem, fast. In Matthew 17:21, Jesus teaches that a particular type of demon can only be cast out by fasting and prayer. Other types, it appears, can be cast out with a command. Fasting is helpful in overcoming addictions, such as to nicotine and other drugs. This is because addiction is a spiritual problem as well as a physical one.
On a mental level, it teaches you to deal with your hunger. Have you ever been driving home and been so hungry that you decide to hit the drive through first? Don't you have (healthier) food at home? If you have ever fasted, you realize you can make it home, and don't "need" to eat right now. It teaches you what hunger really is. So you are more apt to realize that you might not be hungry, but actually bored or depressed or thirsty. It also teaches you coping mechanisms to deal with actual hunger. What else could you do instead of eat when your a little hungry right before bed? It will also give you an appreciation of how food tastes. You take some things for granted. If you don't eat them for an extended time, you appreciate them much more. I broke a fast at Shabbat dinner, so the first thing I ate was grape juice and challah. I had no idea just how sweet challah was. Sure, grape juice is sweet. But challah is, too.
There may be health benefits to occasional fasting, like detoxification, reducing chronic inflammation, quieting allergic reactions, etc. But that's secondary, in my opinion.
Fasting has various intensity levels. One day a year, on Yom Kippur, observant Jews abstain from EVERYTHING. No food, no water, no brushing teeth even. You can do anything for 24 hours. It isn't easy, especially going without water. But you are more than your body, remember. You'll live through it. And it's only sundown to sundown, so as soon as it is over, we have a meal and drink a good bit of water.
Another level of fasting is just abstaining from food, while still drinking juice. This is sometimes called a "juice fast". I have friends that do this occasionally.
Another level is called a "Daniel" fast. In the Book of Daniel, the Prophet ate only vegetables and fruit, and drank only water for 10 days. Later, he went on a second, 3-week fast. To quote the Bible, Daniel "ate no pleasant food, no meat or wine."
For Roman Catholics, there is a form of fasting that limits food intake to two small meals a day, both of which don't add up to one regular meal. During the Lenten season, denying your self one pleasurable food is a form of fasting.
If you have never fasted before, you may have to work up to this. I know people who have a hard time just skipping lunch. The longest I have fasted is a week. I have a friend that was having a major problem in his work environment. He decided to fast by skipping lunch, and praying during that time, until the problem was resolved. He had no idea how long it would take. It really depends on your spiritual situation.
Moses went without food or water for 40 days, but he was in the presence of the Lord. Jesus fasted for 40 days, but he WAS the Lord. In the book of Esther, she entreats the entire Jewish population to not eat or drink for three days. But then, they were about to be annihilated as a people. I wouldn't suggest going on a long fast unless there was a major spiritual reason to do so. Moses was receiving the Torah from the Lord. Jesus was preparing for his earthly ministry. You are probably not at the spiritual level of either of them. If your entire family is under threat of being annihilated by an evil provincial governor, then you may want to fast for a long time.
If you are a religious person, I would suggest that you follow your faith's existing fast protocols, if any. For Judaism, this starts with Yom Kippur, but also includes these minor fasts. In Islam, fasting is one of the five pillars, and one should fast during the daylight hours of the entire month of Ramadan. I am not familiar with Islam enough after that. In Christianity, there are varying "fast days" depending on the denomination. The Roman Catholic Church does have specific fast days and regulations. The Reformation movement rejected the canon law of the Catholic Church. Protestants and Evangelicals are encouraged to fast, but with no dogmatic rules on how and when.
If you are not a religious person, start occasionally skipping a meal. Then try going an entire day without food, but with water. Don't try to fast without drinking water for more than one day.
I have another friend who fasts almost every other day. I do not recommend this, but he has A.D.D. and knows he has a problem controlling how much he eats. To counter act his over eating, he just doesn't eat for a time.
Fasting for an extended time can give you really bad breath. Eating parsley, while countering the idea of fasting, can help alleviate the problem.
In Judaism, the very young, the very old, and the infirmed are all exempt from fasting.
There are medical conditions that are contraindicative to fasting, so check with your doctor first. Diabetes comes to mind as an obvious one.