I mean that they should do this! You cannot evaluate how you will react from someone else's experience. This is basically the survival part of the NOLS courses. Other organizations and the military also do these kinds of exercises. You need to do it with others to be safe. If you hike off-trail regularly, then do it off-trail; if you hike on trails, then do it on trails. You also need to be sure you do not have some metobolic disorder that would make this unsafe. Most people in the USA have never even gone without food for one day, let alone four. You also need to be in the real situation - not sitting in your house! Obviously you need to learn your survival skills before this "test". To be conservative - first do a 2-day survival, then a 3-day and then a 4-day. This is an exercise without food, NOT without water.