I see two problems to address in this question, one ancient, and one very modern.
The ancient one was stated by Aristotle as "the problem of will" in which he says, "We know the good, but we do not do the good." In this case, moderation is good, but greed, excess, addiction, and even excessive deprivation (such as anorexia) are tendencies we fall into. Although most people no longer use the 7 Deadly Sins, it is worthy to note that at least four of them (lust, gluttony, greed, and sloth) are immoderate.
The solution to this ancient problem lies in what some call self-discipline or inner discipline. The East never saw a philosophical paradox in the problem of will, probably because the self-discipline of meditation is part of yoga, meditation, and qi gong. It was seen as a challenge, but not a paradox.
More recently, we've begun to understand how to develop genuine, non-repressive self-discipline through the field of emotional intelligence, a sub-field of psychology.
The second issue is modern. For over 100 years, clever marketers have realized that nothing sells like addictive substances: nicotine in cigarettes, cocaine in the original Coca-cola and Pepsi formulations, later replaced by caffeine, refined sugar, and more. In fact, there are over 2,500 addictive substances that can be added to foods and beverages for "enhancing flavors" which do not even need to be listed on the label.
Thus, unless we are very careful, we are subject to ingesting addictive substances and becoming addicted before we even know it. And, once the brain chemistry of addiction kicks in (no matter what the substance or habit, though some are worse than others), it is much harder to stop the addictive impulses of the body.
Thus self-discipline, essential for moderation, always difficult, is much harder now.
In my own experience, learning self-discipline, detoxifying the body, and "re-wiring" the brain for moderation, as difficult as it is, has uncounted wonderful rewards.
As life coach Dan Millman puts it, "Discipline equals excellence; Excellence equals freedom."