[cabinguy]

I've done a 12 day fast. The first 4-5 days were extremely difficult (caffeine withdrawal didn't help) , but by day 6, I had a feeling of euphoria. My original goal was a 10 day fast, but I didn't want to give up the clear mind and energy I was experiencing, so I extended it to 12 days.

I think this is a pretty common experience. You don't start feeling the "good feels" until you get past the 4-5 day mark.

Anyway, this was about 7-8 years ago and I haven't tried again since, but I often think about it.

For what it's worth, I do IF as a lifestyle (18:6). Basically (for me) it's a very easy way to help restrict calories. Hopefully there are some health benefits, too.