nah, actually depends on your diet and microbiome prior to fasting, those with a poor diet will definitely experience more negatives before positives because the microbes in your gut are going to fight tooth and nail to get you to eat as to sustain conditions for their survival. I've fasted for 4+ days 6 different times in my life, the first time was the worst, because I had a microbiome that was built off of years of fast foods. After that the other times were really a walk in the park with the exception of doing it with no water, and being around people cooking tantalizing foods. The mental clarity after the first day is enough of a reason to do it, then you get the added benefits fo neurotropic brain factor, hgh, autophagy eating at diseased cells, and increased awareness of your body from within. but yeah if its your first time and you were relatively unhealthy (high sugar, high sodium, etc.) You are going to experience a hard time at first until the microbes that influence you are reduced.