"Autophagy", that famous process which supposedly happens during fasting, that miraculously regenerates us, actually happens during caloric restriction, and it's actually a daily process that happens during the night, in everyone, while glycogen stores get naturally depleted.
And we have no evidence that increased autophagy levels are beneficial, quite the contrary, we have some evidence that, right after fasting, the immune system is suppressed. The bigger the caloric restriction, the larger effect on refeeding. An effect very relevant for malnourished populations that suddenly get access to food.
This is basically modern quackery, medical technobabble lacking any evidence other than obscure studies done on mice.
What "healers" and witches used to do, but taken to the next level.
And unfortunately it is also a recipe for serious eating disorders. Hello anorexia.