I'm curious about traditional Korean medicine diet.

How is traditional Korean medicine diet created? I heard that they examine your body type and tailor it to each person, is that really true? But does the weight only come off while you're taking it, and if you stop eating it, do you gain weight again? I see many people around me taking it, and it seems almost the same. I thought that through herbal medicine, your body type could be improved so that you wouldn't gain weight even if you stopped, but it seems that's not the case. Is that correct?