(Concern) Diet herbal medicine

I've heard countless times since I was young that you can lose weight with herbal medicine.

I can't tell if it's really effective or if it's just a rumor that spread from person to person, but a friend I used to be close with in the past told me she was taking herbal medicine for dieting.

And then, after some time had passed, we met again, and she had lost quite a bit of weight.

So I asked if he did any kind of exercise, but he said he didn't do anything special and just took diet herbal medicine.

And then she said that she really goes to the bathroom very often.

At that time, I was skeptical, thinking that the diet herbal medicine didn't actually improve my constitution or anything like that, but rather induced diarrhea or something similar to temporarily cause the body to expel water or stool, resulting in a temporary weight loss effect.

And a lot of time has passed, but the distrust that arose back then hasn't been resolved.

What functions do diet herbal medicines have and how do they help with weight loss?

I'm very curious and I want to resolve any preconceived notions I may have had during this opportunity.