Fasting has a lot of well-documented benefits. Unfortunately, most of us can't slow down enough to really benefit from it.
As an Orthodox Christian I fasted for years - too many details that will bore everyone, as most 'fasting' days are actually vegan days, but there are times that observant Orthodox truly go without all food (and water, for the advanced) for a number of days. And then eat vegan, once daily, for a number of weeks. People don't die from this.* We can get along on much less than we think.**
Then I lost faith, lost sight of a lot of stuff, stopped fasting for a few years. Diagnosed with cancer. Lesson?
No lesson. Cancer happens. Maybe I would've been diagnosed much earlier without the fasting, but who knows?
*providing they weren't cachectic already.
**there's a news special available on youtube about an Orthodox monastery on Mt. Athos; the monks are physically active, eat a plain meal of vegetables twice daily, and there is nothing for the MD/monk to do. No cancer, no heart disease, no diabetes, nothin'. Just monks who live to be ridiculously old and then die peacefully. Of course, ymmv.