I am always surprised when someone asks me if they should try a quick diet or a 3 day fast. I even get people asking me "is 7 day slimming pill safe?" To which I answer, "a better life long eating pattern is the safest." You can't rush your body, you have to let it adapt to healthier living over a period of time.
Don't for the instant results that fail in the long term. Go for change that is permanent.