While achieving dramatic results from your fitness program in a short period of time is possible, the probability of sustaining your results for a long time is very unlikely. It takes me 16 weeks of intense exercise and very strict dieting to get ready to compete in a bodybuilding competition, and I cannot sustain that peak physical condition for very long. So, buying into those quick fix programs is a waist of your money, because you can't keep up the effort it takes to sustain the results for the long-term.
Staying healthy and fit is a lifetime effort which is most easily accomplished through balance and moderation in your diet combined with regular exercise. The quick fix approach is just a short-term answer to a long-term problem.