Ah, thanks for clarifying. I've got several friends who believe in various forms of the pH diet. They also tend to be folks who believe in a lot of other woo, so I'm a bit trigger happy in shooting down pH-based diet theories (those diets are particularly ridiculous because they often categorize quite acidic foods into the alkaline category and vice versa). If there's ever been a good study about it, I'd certainly read it.

I think there's a lot of superstition in general, but one could certainly have independently noticed that eating sugar or fat alone (say butter or honey) is somewhat self-regulating. You get sick of it pretty quick. But, put them together in a pie or pastry or donut or something and suddenly it gets really easy to eat hundreds of calories worth of sugar and fat in a few quick bites.