There's mixed science on the cellular benefits particularly when it comes to tumors. When the cells rapidly repair coming off of fast, there's potential for it actually increase tumor growth potential. If the science was clear and positive, but would be a huge motivating factor - but that's not the case. I wish it were, but it's not that clear cut.

However, there’s a caveat: if cancerous mutations occur during this regenerative phase, the mice are at a higher risk of developing early-stage intestinal tumours."Having more stem cell activity is good for regeneration, but too much of a good thing over time can have less favourable consequences," said Omer Yilmaz, an associate professor of biology at MIT and the senior author of the new study. Intestinal stem cells help to renew the lining of the intestine, which is replaced entirely every five to ten days.This rapid division makes them more likely to develop precancerous changes than other cell types in the intestine.

Anyone have evidence of a multi-day fast doing anything? Sometimes I'll fast a day if I'm sick or something which is rare but why multiple days?

Came across this just by chance scrolling X.