Common pharmaceuticals (even vaccines) have known (and some extremely debilitating) side effects.
While the conclusion seems reasonable (ie, some people have adverse affects to not eating) it's by no means a condemnation of fasting.
Fasting is the universal method of allowing the body to heal itself, animals fast to heal naturally. (ie, no medicine actually heals only compliments/supports healing, the body does all the real work)
Check writings by Valter Longo. The two principles are autophagy during the fast getting of bad cells (precancerous, etc...), and hormones typically only present in kids during growth periods reappearing during refeeding (eating after fasts longer than a few days).
Wive's tales and home remedies still circulate because they often work. Of course, you're not going to read that on Hacker News because it's biased by people wearing modern American blinders that don't have the humility, courage, awareness or something else, to just try for themselves. I was that way until I tried psychedelics, meditation, pranayama breathing, lucid dreaming and many other alternative modalities just two years ago.
Scientific rigor is not just about gathering people as lab subjects, experimenting on them and publishing your findings in peer reviewed journals. In my experience, the strongest science, where the deepest knowledge arises, is by systematically performing experiments on yourself. This isn't possible for all things, but it's 100% available for fasting.
Animals fast on purpose to facilitate healing? Do you have a source for this? I suspect some are forced to fast because they are too injured/ill to obtain food.
A positive impact from entering a massive caloric deficit when the body is actively burning calories is counter-intuitive.
Not GP. I don't remember where I read it about wild animals, but my dog would have the occasional "low energy, don't want to play" day, followed by a couple of days of not eating, and then being super-energetic when he went back to eating.
On one of these occasions, I took him to the vet, who said he had a fever, likely of viral cause, and that him losing appetite was perfectly natural and likely helping him heal.
When I'm sick I lose my appetite (and don't eat, sometimes for a few days).
The positive impacts of fasting are supposedly due to increased efforts by the body to scrounge and scrape for calories, which up-regulates processes that have the effect of clearing undesirable built-up matter/cells/etc.
While the conclusion seems reasonable (ie, some people have adverse affects to not eating) it's by no means a condemnation of fasting.
Fasting is the universal method of allowing the body to heal itself, animals fast to heal naturally. (ie, no medicine actually heals only compliments/supports healing, the body does all the real work)