On Fresh Air Thursday, Terri Gross interviewed David Linden, author of The Compass of Pleasure: How Our Brains Make Fatty Foods, Orgasm, Exercise, Marijuana, Generosity, Vodka, Learning, and Gambling Feel So Good. He had a lot of interesting things to say about pleasure, about genetics and about addiction. What interested me was "fatty foods" at the top of his list. Those of us with a genetic propensity for brain alteration through pleasure (the way our bodies respond to dopamine production) means that anything that makes us feel good, we will want more of, even after it no longer makes us feel good.
Sugar and fat are an addictive combination for those of who focus compulsively on one pleasure at a time and we become just as addicted to them as nicotine or alcohol or sex. Unfortunately, the brain alteration that occurs is permanent. That's why we cannot go back to our naive use of a substance or behavior once we've become addicted. And it is clearly, in his opinion, physiological although our original impulse may be to relief stress (emotional/psychological), eventually the physical part of the brain is running the show.
This confirmed a lot of stuff for me. You might enjoy listening to his podcast on NPR.