Just a personal observation. Way back when, in my twenties when I was doing a macrobiotic diet, I did a thirty day water and juice fast. After the fast I developed several issues that the doc said were a result of the fast. My metabolism sank like a rock - from then I cannot eat more than 1200 calories a day without gaining weight - doc said the fast made my metabolism super efficient because it had gone into starvation mode. And I developed some severe digestive issues that lasted for a very long time. I might add that I did the fast for health, not spiritual, reasons. I would not do it again. I did not see any positive results, from a health perspective. I have done shorter fasts for spiritual reasons, without obvious health problems resulting.
That is just what happened to me. I eat carefully and healthy now. I am lacto vegetarian, emphasis on organic fruits and veg and whole grains. I eat three times a day as I tend to develop very low blood sugar and faint if I go more than a certain number of hours without eating. Maybe because I am old.