Is taking constipation pills every day to lose weight bad? Why is it or why is it not? (a friend did and lost 25 lbs & is in good health)

No! Do not do that. It is dangerous. First, the only weight you will lose is stool and water weight - not fat. Second, you will lose lots of electrolytes and nutrients as well as good gut bacteria. This all can lead to heart, nerve, and brain problems as well as kidney damage. That is not the way to lose weight.