5 days is longest I’ve done. Day 2 and 3 are hardest. Day 4 and 5 are much easier. Eating ketogenic in the several days to weeks leading up to it makes the fast much easier. When doing it in the summer and sweating a lot from work outside I had to add salt to avoid passing out. So now routinely will eat/drink more salt if fasting. Some vitamins inhibit autophagy so I stop vitamin supplements with fasting. Jason Fung is the person I think has most helpful info on the topic. Depending what meds people are on they may need to decrease/stop them in order to make fasting safe. 

 Thank you! What did you eat the first day / few days after? Will checkout JF 

 Usually just start with smaller amount of things I commonly eat. Meat, eggs, bone broth, maybe small amounts of veggies. I’d suggest avoiding more processed foods i.e. things in boxes, cans, and bags all the time but especially after fasting.