Can normal weight be achieved through diet pills to the point of extreme thinness?

I have an average body type but want to lose weight with diet medicine.
The price wasn't cheap, but from the people I know who have taken it, the effects seem definitely noticeable.
But my friends all stopped taking diet herbal medicine at the same time and said they experienced a huge rebound, so they advised against continuing the medication.
Are the side effects of diet herbal medicine really that severe? Is it true?
Is it true that my liver enzyme levels have worsened and that I am becoming someone who easily gains weight?
I'm worried whether I really have to take diet medicine for the rest of my life once I start.