Using the same supplements for months at a time without changing up the routine puts your body in a state of boredom. The body builds a tolerance for the supplements it consumes consistently. If you have been taking the same things day in and day out for longer than 6 months then change things up and watch the results. If you like the supplements or vitamins you are taking to enhance your weight loss, but have noticed that they have been less effective, take a month off the supplements completely. This will help the body lose the tolerance for the supplement so when you start again, it will be in full effect.