After experimenting with fasting off and on for years, I don't do over 36 hours anymore. Somewhere between there and 48 hours I get cold.

If you got cold, your thyroid hormones started going nuts. This is the "starvation mode" where your metabolism slows drastically. Dead slow metabolism is not good for you and is why many dieters struggle with yoyoing weight and every diet getting harder to see results.

You'll do better for your long term health to refeed and then start a new 36 hour fast.

The long numbers for fast times are just like any other health fad. Fasting is good and a few influencers pick it up and start shilling it for views. Then everyone has to escalate to stay on top of the view charts so the easy escalation is to promote longer and longer fasts.

But what do I know? I'm just a martial artist who noticed that even though I felt great sitting around at 84 hours past 36 hours I start getting my ass kicked by people I usually beat easily. So I started digging more into the science. Turns out an endorphin dump isn't always good. Performance is a better measure than sensation. Remember that people feel warm right before they freeze to death. They feel so warm that people who froze to death are often found naked.