Here’s my vague understanding of why this happens with melatonin; if someone can correct me I’ll have learned something.

Taking supplements your body naturally produces, like melatonin, creatine, and some weight loss products in large doses makes your body turn off its own production. You’re also training your body to process and live with more than it needs, and considering it always wants to reach homeostasis, you end up needing more of it to have the same effect (like many drugs).

Back in the 90’s a lot of people on diet pills ended up gaining a lot of weight back once they stopped taking the pill because their bodies took a long time to produce the same chemicals naturally, having essentially been overdosed for a while.

Yes but it’s risky. The poop on the 4th day may make you have to retile your bathroom.