The same cycle happens--effective for a while and then not so effective anymore.
What I recommend is to stick with simple organic fitness routines--workout, eat balanced, eat natural, relax and have fun.
It's the natural movement of marketing--now and then they come up with a new product, a new gimmick. It doesn't really help much--often they have the same ingredients as what old products have--but they highlight an ingredient (or invent a so-called "super" ingredient) and then do extra promotion on it.
They usually hire models who are already fit and healthy (not due to the benefits of the products promoted) and then make false claims and testimonies of how the models ended up with such fit bodies since they used the products.
Don't go for that crap. You see this online and on TV. And I'm amazed at how people are easily duped about them.
Well, it isn't bad to try one really good product now and then. Make sure to study their pros and cons first before you buy. But most times, all you have to do is stick to the 5 organic and simple routines mentioned above which often really works for everyone.
And you know what? The vitamin you often only need is natural Vitamin C.
So, beware of fitness fads. Go for the simplest and most organic.