That paragraph is saying that for what you are trying to accomplish can be done w/ diet & training. In this case, specifically diet. This doesn't involve putting foreign substances into your body that can introduce their own effects on your body (expected or not) and then either leave you in a different "state" that your body needs time to recover from or the effects will leave if you go off whatever you were on. With a diet, you are simply modifying the times you eat, what you eat, the combinations of what you eat and the amounts you eat. Since you need to eat anyway, you aren't introducing anything foreign into your system and you also get a much better handle on how your body responds to the changes you make in your diet. Since you are really changing a behavior (how you eat), the results will follow your behavior, which can be translated into a sustainable lifestyle.
As Shadow would prefer it, the shorter response is basically saying no pill, AAS or supp, will produce more predictable, easier to adjust, easier to maintain and cheaper results than just changing your diet.
To your last post saying that you think your diet & training are good enough already, as Dr. Phil says, "How's that workin' for ya?" You aren't getting the results you want with your current approach are you? (That's why you are posting this thread.) So let's take a look at what you are doing and see where we can tweak it. Often the tweaks are not major but there is optimization that you can do to get the results you are looking for.
Post up what you eat on a typical day and let's start the analysis!