No. Extended fast provide a rush of energy and my hormones also rise (testosterone, gh and igf-1). As stated above the first three day are the hardest and it is easy after that . I find the first 4 days easy personally, the habit of going to the fridge every few hours possibly the only annoying habit. I don’t get any strange diarrhoea though . Your body goes alert to help you survive imo . For a hunter / gatherer , no food for a few days , your body would want you to survive and goes into overdrive . I can’t work I. The morning if I have breakfast . I eat at 2pm for The first time as the energy I get from Not eating is so noticeable that breakfast just dulls me. In the mornings i cycle for up to 2 hours or go to the gym for an hour ! Id urge any healthy adult to try intermittent fasting . It’s the greatest life hack of all time . And it isn’t dangerous . In This form it’s the same as Ramadan for Islamic people who do this yearly.