Are fake doctors giving you drugs in the form of medicine to cut on weight ?

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I just saw the movie " Requiem For A Dream " and was horrified to see how a sound old lady turns insane , after she visits an unqualified doctor , who gives her some pills to cut weight , those pills have huge side effects and disturbs the lady's mental balance ! Is this something happening in real life ? Do we need to recheck on what pills are we given ?