Fasting.

As a muslim I am required to fast for one month during the month of ramadan. The fasting is from sunrise to sunset. During the period you cannot take anything even a drop of water. It is a marvelous feeling after you break you fast. You will look forward to the next day. Try it.

I have never done fasting, though it is biologically good for health but it depends upon one will power to control yourself

I have fasted for 3 days, water only. You know how you think you have nothing in the house to eat and you just have to go to the store and get something? Well when you're fasting, it's amazing how much food you find in the house that's very tempting. The main thing that's hard is your brain is hardwired to chew, so you feel like something's missing. It does get easier the second day and the third you're not counting the minutes til your fast is up, you've kind of settled in to not eating as norm. When you come off a fast, even if it's only 3 days, don't go have a big steak dinner! Start out with some hearty vegetable soup, and work your way up to your normal diet or your digestive system may go into shock. Meat and dairy are harder for your system to digest, so get it restarted with veggies. This is not only a good spiritual exercise, it's good for the body. All the energy you normally use to digest food is used elsewhere, plus all your digestive tract gets emptied out, so you can start over again.