There are entire sects of people in India that do 5-10 days of fasting many times a year [1]. This has been going on for thousands of years. Personally I know 3

There are entire sects of people in India that do 5-10 days of fasting many times a year [1]. This has been going on for thousands of years. Personally I know 3 people who fast like that. And they all look 10 years younger than they are, have lot of energy and focus. This may be anecdotal. For example they also only eat vegetarian and don't drink any caffeine. But they claim that fasting helps them a lot. [1] https://en.wikipedia.org/wiki/Fasting_in_Jainism https://en.wikipedia.org/wiki/Fasting_in_Jainism