I am sure fasting proponents promise way too many things, but the underlying cell cleanup mechanism [0] is very real and received the Nobel Prize in 2016 [1]

[0] https://en.wikipedia.org/wiki/Autophagy

[1] https://pubmed.ncbi.nlm.nih.gov/27912049/

The wiki page does not mention fasting.

> fasting and CR [calorie restriction] are the most potent non-genetic autophagy stimulators, and lack the undesirable side effects associated with alternative interventions.

> We conclude that both fasting and CR have a role in the upregulation of autophagy, the evidence overwhelmingly suggesting that autophagy is induced in a wide variety of tissues and organs in response to food deprivation

From: https://pubmed.ncbi.nlm.nih.gov/30172870/

I have multiple relatives who are aging researchers.

Fasting is healthy and normal. Many humans historically regularly "fasted" by today's standards just by going 12+ hours between modest meals.

We know that it slows signs of aging, but it can also depress the immune system (which might be why it slows aging), so it can still cause you to die young.

The effects of fasting on all-cause mortality are generally positive, but it's unclear right now whether that means people need to do uncomfortable levels of fasting or if most of us are just killing ourselves with eating too much and too often.

FYI: https://www.nih.gov/news-events/nih-research-matters/fasting...

But as to the mechanism... not a scooby.

> Long periods of fasting between meals helped male mice live longer and healthier lives, regardless of the content of their diets. More studies are needed to confirm these results and understand how different fasting periods may impact health.