I'm curious about the side effects of diet herbal medicine.

As summer begins, interest in diet herbal medicine has increased.
However, among the people I know, they all say that as soon as they stop taking diet herbal medicine, they gain twice as much weight.
Are the side effects of diet herbal medicine really severe?
Is it true that liver enzyme levels worsen significantly?
Is the effect of the diet medicine to suppress appetite or to reduce body fat?
I'm wondering if there is a diet herbal medicine that can be taken without side effects.