What is this conjecture based on?

There is a lot of evidence to suggest that fasting, and even intermittent fasting, is a good thing (actually, I seem to recall some papers/articles have ended up on HN). Fasting has also been shown to regenerate the immune system[1]

Besides, I have enough body fat to supply calories for a good bit longer than 5 days :)

[1] https://news.usc.edu/63669/fasting-triggers-stem-cell-regene...

Depends who you ask. I did a 12 day fast once, nothing but water. I intended to do a 10 day fast, but I felt so wonderful, so healthy, so clear, that I decided to add 2 extra days.

For those interested, most of the benefits (for me) happened after the 5th day. Thats when the hunger and caffeine withdrawal ended.

I don't know all of the science behind it, but I can honestly say that I never felt better/healthier in my life.

3 days and your immune system "reboots." Not sure if anything after that helps but an extra day or two hardly sounds troubling.

Depends on the person. Angus Barbieri completed a 382 day medically supervised fast in 1966. Depending on body composition and physiology, one might reap a lot of benefit from simple intermittent fasting while another person might continue fasting for longer stretches to help reset their body to more normalized hormone levels.

As is often the case, it depends on the context. For someone obese and/or diabetic, extended fasts of 3-7 days as recommended by Dr. Fung can be very beneficial.

Why do you think that?