I’ve been fasting for 4+ years and have really loved it. It’s been a little while since I’ve done an extended fast, and I just finished a ~50 hour fast. At around the 36th hour I started feeling euphoric and my senses were absolutely heightened (I felt like imagine a tiger might stalking its prey). This all came with a mild headache, but it was definitely a pretty amazing feeling. I did some reading on it and apparently one type of ketone, BHB, can act like the drug, GHB, by activating GABA receptors. Also found an interesting article on fasting’s effect on the microbiome
I just finished a 43hr fast. It was unintentional. I was only aiming for a 20hr fast but I didn’t feel hungry and felt great so I continued. I definitely experienced the euphoria/well being and by hr 40 I did have a moment where EVERYTHING was so clear and I just slowly stared at objects in my room as if it were the first time I’m really seeing them. I felt like I had super human senses. It was a very cool experience and I was incredibly alert and very productive all day!!