Fasting is one of those things. I get annoyed every time someone mentions fasting because it’s always done in a weird way. As though, simply by ignoring food, you have become spiritually mature.
Near as I can tell, the Bible never says we should fast. Fasting, if anything, is more assumed or mentioned in passing that someone was doing it. There is no fasting command.
All that being said, I’ve done it. The first time I did it was just to see what it was like. I read a book about this guy who almost died of starvation and he started having hallucinations. Cool. I planned on seeing how long I could make myself go without food. I made it 60 hours and then ate manicotti. No hallucinations.
I also did it one day a week for a few weeks, 24 hour long deals. The point of fasting is to develop self-control. The battle of the flesh takes over and you hear your flesh’s justifications, “Oh just eat food. You’re the idiot depriving yourself, who cares if you eat? Hey, you’re under grace anyway.”
It did help me lose weight. It also helped me eat less on other days. Did I find spiritual benefit from it? Actually, yes I did. It did work my self-control and put my flesh battles in perspective. I found it helpful, which is why I think people do it.
I’d recommend giving it a try every once in awhile, just to get those self-control muscles working again. Also, trying not to tell anyone you are doing it while doing it is another battle of self-control. It’s fun stuff.