It seems there is renewed interest in periodical fasting. What are the basic ideas?
First, an idea is that fasting turns on ‘garbage collection’ in body. The key time span seems to be 16 hours – at about this point, the mechanisms kick in. This is real fasting for 16 hours (no food or drink, except water).*
*This is easier than you might think. Finish dinner at 6pm. Wake up the next morning at 6am. You have now fasted for 12 hours. Wait until 10am. Voila, 16 hours.
Second, an idea is that fasting allows for the digestive system to heal itself more efficiently (I am guessing because you have less or no food in it after a period of time). It seems various health issues are linked to unhealthy digestive tracts – allow the digestive tract to heal, and you solve the problem to a large extent.
For contrast, consider how fasting is being treated in this new movement as opposed to how fasting is treated by the Catholic church for Lent. The Catholic church now has a watered-down version, where the time is reduced and ‘fasting’ is now meant to include 3 snacks during the course of a day.
It seems plausible that watered-down religious practices no longer do what they once did – that calling something, in this case, ‘fasting’ doesn’t mean it is, and doesn’t mean one can expect to get the results that people in the past would (even when it comes to building will-power, a traditional reason given for periodical fasting).