A three or four-day water fast can lead to feeling unwell for the first one to two days, followed by a significant improvement in well-being and a lack of hunger.

“When he does a three or four day water fast, the first day or two, he feels like crap. I'll just say up front, don't do it if you've got an important meeting or business trip or anything. Don't be-- CHRIS PALMER: This is just consuming water. ANDREW HUBERMAN: No black coffee? CHRIS PALMER: I usually tell him he can have plain black coffee or tea. But-- ANDREW HUBERMAN: You have mercy after all. CHRIS PALMER: I have a tiny ounce of mercy. But when he does it, his blood sugars plummet in a good way, his blood sugars are normalizing. But the last time he did it, he actually got to seven days at one point. And he said, I feel great.”

“When he does a three or four day water fast, the first day or two, he feels like crap. [...] And he said, I feel great. I want to keep going. I can't believe that I'm not hungry. But I am not hungry at all. I don't miss food at all.”