The brain permanently swings between necessity and pleasure. This is the whole issue of the relationship between two key areas called the arcuate nucleus and the nucleus accumbens. The former, which is located in the hypothalamus, is part of the brain stem, i.e. of what is sometimes improperly called “reptilian brain”, the realm of instinct. There sits the need to eat in order to assuage one’s hunger. The nucleus accumbens, on the other hand, belongs to a less “archaic” part of the brain, which houses the headquarters of hedonism, and therefore handles the reward system. The balance of these two systems plays a key role in our eating behavior and our behavior at large. Hedonism involves behaviors such as the one described in the famous ‘episode of the Madeleine’ in Proust’s Remembrance of Things Past: the brain is eager to experience again a pleasant sensory recollection. It responds to a correlation between a taste and the memory of a pleasurable instant. This element of pleasure explains why each of us is partial to one ‘Madeleine’ only, instead of a dozen… and why it is never boiled fish or broccoli! As a rule, our happy memories recall lipids or carbohydrates, and ideally a hard to resist combination of the two. As long as our metabolism and our hedonism (our eating behavior) work hand in hand, we remain healthy; any discrepancy between them brings health disorders, and if our hedonic quest encourages us to go against our metabolism, we fall prey to addiction and/or disease.