Anyone who has worked in the field of addiction has seen individuals, even the most severely addicted, after detox control their addictive behavior at least for a short period of time. Twelve-step programs emphasize the importance of avoiding people and places and things associated with the addiction. In other words, the avoidance of temptation. And individuals who do not heed this advice often find themselves relapsing into their addiction. Those who fall back into their addiction often say that it was just too hard to avoid the temptation. And, indeed, there is a growing body of research that shows that resisting repeated temptation takes a mental toll.
This theory, which is known as willpower depletion, likens willpower to “a muscle that can get fatigued from overuse.” But willpower depletion isn’t just physical fatigue. Recent research has suggested that when willpower has been repeatedly tested, your brain may actually function differently. Brain chemistry changes. Other research has suggested that individuals who are being depleted of willpower may be running low on brain fuel, e.g., glucose. Human subjects in one study who had exerted willpower in lab tasks had lower glucose levels than control subjects. In another study, the researcher found that drinking sugar-sweetened lemonade restored willpower strength in depleted individuals while drinking sugar-free lemonade did not.